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G4beamline User`s Guide

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1. Event 1 Completed 1 events realTime 1 sec 1 0 ev sec Event 2 Completed 2 events realTime sec 2 0 ev sec Event 3 Completed 3 events realTime 1 sec 3 0 ev sec Event 4 Completed 4 events realTime 1 sec 4 0 ev sec Event 5 Completed 5 events realTime 1 sec 5 0 ev sec Event 6 Completed 6 events realTime 1 sec 6 0 ev sec Event 7 Completed 7 events realTime 1 sec 7 0 ev sec Event 8 Completed 8 events realTime 1 sec 8 0 ev sec Event 9 Completed 9 events realTime 1 sec 9 0 ev sec Event 10 Completed 10 event realTime 1 sec 10 0 ev sec Event 20 Completed 20 event realTime 1 sec 20 0 ev sec Event 30 Completed 30 event realTime 1 sec 30 0 ev sec Event 40 Completed 40 event realTime 1 sec 40 0 ev sec Event 50 Completed 50 event realTime 1 sec 50 0 ev sec Event 60 Completed 60 event realTime 1 sec 60 0 ev sec Event 70 Completed 70 event realTime 1 sec 70 0 ev sec Event 80 Completed 80 event realTime 1 sec 80 0 ev sec Event 90 Completed 90 event realTime 1 sec 90 0 ev sec Event 100 Completed 100 events realTime 1 sec 100 0 ev sec Event 200 Completed 200 events realTime 1 sec 200 0 ev sec Event 300 Completed 300 events realTime 1 sec 300 0 ev sec Event 400 Completed 400 events realTime 1 sec 400 0 ev sec Event 500 Completed 500 events realTime 1 sec 500 0 ev sec Event 600 Completed 600 events realTime 1 sec 600 0 ev sec Event 700 Completed 700 events realTime 1 sec 700 0 ev
2. radius The radius of the cylindrical particlefilter mm innerRadius The inner radius of the cylindrical particlefilter 0 mm solid height The height of the rectangular particlefilter mm width The width of the rectangular particlefilter mm length The length of the particlefilter mm maxStep The maximum stepsize in the element mm material The material default parent s color The color of the particlefilter white decay A comma separated list of particle names to decay kill A comma separated list of particle names to kill keep A comma separated list of particle names to keep nWait Intersection to do the kill default 1 referenceWait Intersection for reference default 1 require Expression which will kill the track if zero steppingVerbose Nonzero to display track kills decays Synonym for decay Interface to the Geant4 General Particle Source 1 10 14 TJR The Geant4 General Particle Source GPS is a very flexible and general way to generate events It is controlled by Geant4 commands which should follow this command in the input file If you have a macro you can include it using either the G4beamlin include command or the Geant4 command control execute Note that G4beamline only recognizes Geant4 commands when the is in column 1 G4beamline User s Guide 73 physics 1 10 14 TJR Due to the design of the GPS only one partic
3. To plot sigmaX and sigmaY using gnuplot do plot profile txt using 1 4 with lines profile txt using 1 6 with lines HistoRoot can also be used to plot profile txt Note the simulation ends when tracks start leaving the world making the number of tracks in the bunch drop below 95 of the initial number around meanZ 10000 NOTE the spacecharge command currently has the limitation that the reference particle must be parallel to the z axis The spacechargelw command uses no reference and has no such limitation but is computationally limited to about 1 000 macro particles nMP 5000 takes 3 min on my Mac gives same plot as nMP 50000 The default deltaT is 0 100 ns which may well be too large for practical use 1 10 14 TJR G4beamline User s Guide 114 7 m Bunch parameters Beam parameters percentil percentil param unse param unse param unse parallel param unse EEEF E a physics QGSP BERT disable Decay nMP macro particles totalCharge total charge of the bunch number of et totalCharge 1 makes spacecharge negligible At the default P 200 the effects of space charge start to become visible around totalCharge 1E10 At 1E12 the focus is very washed out and at 1E13 is gone The default bunch has sigmaX sigmaY sigmaZ 20mm The default quadrupole strengths are scaled with momentum so the focus remains at z 6000 ind
4. Note that event 0 will be ignored as that value of IEVT is reserved for the reference particle 9 4 BLFieldMap Blank lines beginning with are printed to stdout Tesla for B and MegaVolts meter for E data points use different units The input file starts with a set of commands and lines beginning with or are comments Units are mm for coordinates use normB and normE Lines if the to define the parameters FF F FF F F FF FF F FF FF F FF F F F F of the map field components ExX Ey EZ Each command has a specific grid Bx By Bz of the map CJ BEWARE followed by blocks of lines containing the values of the The field component names depend on the type of map cylinder Br Bz Er Ez the parsing is not exhaustive are silently ignored capitalization of argument names but invalid inputs may not be detected and may yield results list of arguments to define parameters For instance invalid arguments which means you must verify the spelling and Correct inputs will yield correct seemingly correct but unintended results The first command is usually a param command arguments 1 10 14 TJR which has the following G4beamline User s Guide 172 a maxline The maximum number of characters per line default 1023 current The current corresponding to this map default 1 0 gradient The gra
5. The idea is to put Zoffset 0 Xoffset 0 stepping Verbose 1 onto the command line or Parameters in the GUD and re run the simulation while varying their values until the reference particle is on the centerline at z1 3000 To speed this up it is useful to temporarily set the beam command s to run one event nEvents 1 To avoid laborious scanning of a long output file with many steps it is useful to use the command line program and pipe it into grep with an appropriate pattern to select a step near or at z 3000 because step lengths can vary it may help to temporarily place an object at z 3000 and grep for it NOTE be sure to look at the reference particle and not any tune or beam particle First keep Xoffset 0 and vary Zoffset You will quickly learn how changes in value relate to distance from the centerline This usually executes in about 3 5 seconds and you ought to be able to find the required value of Zoffset in a few minutes Using the command line history in your shell greatly speeds this up To tune Xoffset you must add this command to make the reference particle visible and white trackcolor reference 1 1 1 I put it just after the beam command you can leave it in Once you have the value for Zoffset then add viewer best to the end of the command and re run it typing run beamOn 1 to the Geant4 Idle gt prompt as indicated by the comments preceding it In OpenInventor select wireframe mode right click DrawSt
6. NYL TESTI UE p Fi ETHANE TISS RIETHYL P UM_DICARBIDE ROPANE ATE RU 4 TISSUE M ROETHYLENE T JUORIDE URANI Ol REA VALINE VITON WATER Kr lXe PbWO4 Galactic _VAP HIT oD Pp CYTOSIN a E E SODIUM MONOXIDE SOFT IC NIUM MONOCARBIDE R XYLENE Cc DIOXID HLORIDE UM IODIDI RIDINE GI Gl Gl IODID pD G EVLAR STAINLESS STEEL CR39 OCTADECANOL E THYMINE URACIL DNA ADENINE DNA 7 GUANINE _THYMINE DNA URACIL DNA AD URIDINE DNA METHYLURIDINE DNA U c i Aliases LHe lHe Air AI Scintil1 Named Argum a Z density pressure POROUS LUC DACRON NOSINE DNA GUANOSIN DNA_MONOPHOS DNA MU Stainless304 Stainless316 lHe PHATE H2 nw I ator POLYSTYRENE ents Density of the material Pressure of the material Atm gm cm 3 temperatur state Temperature of the material K State of the material g l or s G4beamline User s Guide 2O WATER Vacuum Galactic L Effective Atomic Weight of the material Effective Atomic Number of the material H2 g mole J lza H l GI 67 movie multipole
7. 1 10 14 TJR G4beamline User s Guide 110 solenoid Endl coilName Endl current 62 80 solenoid Center coilName Center current 64 44 solenoid End2 coilName End2 current 67 11 TIronShield is the downstream magnetic shield for the detectors tubs IronShield innerRadius 250 outerRadius 750 length 100 material Fe color 0 7 0 7 0 7 t The MIC bl Trackers APPROXIMATION each SciFi station is approximated as 2 0mm scintillator GUESS the vacuum window is 1mm Al flat placed in the center of End2 APPROXIMATION the tracker pipe ends at the vacuum window make room for the Diffuser virtualdetector SciFi radius 150 length 2 0 color 0 0 1 material scintillator tubs TrackerPipe innerRadius 200 outerRadius 255 length 2491 material Al kill 1 color 1 0 1 tubs TrackerWindow outerRadius 200 length 1 0 material Al color 1 0 0 group Trackerl material Vacuum length 2491 radius 0 place TrackerWindow z 1245 0 place SciFi rename Trackerla z 1045 5 place SciFi rename Trackerlb z 595 5 place SciFi rename Trackerlc z 245 5 place SciFi rename Trackerld z 45 5 place TrackerPipe z place SciFi rename Trackerle z 54 5 endgroup group Tracker2 material Vacuum length 2491 radius 0 place SciFi rename Tracker2a z 54 5 place TrackerPipe z 0 place SciFi rename Tracker2b z 45 5 place SciFi rename Tracker2c z 245 5 p
8. virtualdetector place four de Det z 1000 Det z 2000 Det z 3000 Det z 4000 Lace Lace Lace Lace Pl pl Ppl pl 0 0 0 0 Det radius 1000 0 color 0 1 0 tectors putting their number into their names rename Det rename Det rename Det rename Det 6 2 ExampleN02 g4bl The Geant4 ExampleN02 physics QGSP material Pb A 207 19 Z 82 density 11 35 box Target width 50 height 50 length 50 material Pb color 1 0 0 1 10 14 TJR ExampleN02 g4bl mimic Geant4 examples novice N02 APPROXIMATELY G4beamline User s Guide 102 material Xe A 131 29 Z 54 density 0 005458 virtualdetector Detl width 480 height 480 length 100 material Xe color 1 1 1 virtualdetector Det2 width 1344 height 1344 length 100 material Xe color 1 1 virtualdetector Det3 width 2208 height 2208 length 100 material Xe color 1 1 1 1 iyl virtualdetector Det4 width 3072 height 3072 length 100 material Xe color virtualdetector Det5 width 3936 height 3936 length 100 material Xe color beam gaussian beamZ 200 sigmaX 0 sigmaY 0 sigmaXp 0 sigmaYp 0 meanMomentum 3824 sigmaP 0 particle proton nEvents 100 OT ORO O Lace Lace Lace Lace Lace Lace e Det1 Det2 Det3 Det4 Det5 Target z 0 z 800 z 1600 z 2400 z 3200 z 4000 6 3 FieldLines g4bl FieldLines g4bl display magnetic field lines Display magnetic field lines for 5 solenoids uncomment the followi
9. A Synonym for a g mole Z Synonym for z keep A comma separated list of particle names to keep all others are killed ignored if empty kill A comma separated list of particle names to kill require An expression that must evaluate nonzero or the track is killed Generate movie NTuple This command outputs a set of NTuples suitable for generating a movie Named Arguments coordinates Coordinates global centerline or reference default r construct a generic multipole magnet Multipole magnetic fields from dipole through dodecapole are implemented with a cylindrical field region and optional surrounding iron ironLength 0 or ironRadius 0 omits it All fields with positive strengths are oriented so in the X Z plane for X gt 0 beam left the field is purely By Negative strengths are allowed and reverse the field The fringe field computation is not implemented Named Arguments cannot be changed in place cmd fieldLength The length of the field region mm ironLength The length of the iron mm ironRadius The outer radius of the iron mm apertureRadius The radius of the aperture mm ironMaterial The material of the iron region fieldMaterial The material of the field region dipole Strength of dipole Tesla quadrupole Strength of quadrupole T m sextupole Strength of sextupole T m 2 octopole Strength of octopole T m 3 decapole Strength of
10. Each positional argument is X Y Z of the position as many positions as desired can be used The same text is displayed at each position Empty text means use a circular marker The marker or label always faces the camera The default height of text is 12 pixels the default diameter of markers is 5 pixels some viewers have rather narrow limits on sizes Coordinates can b ither centerline or global the default Named Arguments text The text of the label empty gt circular marker color The color 1 1 1 size The size in pixels coordinates Coordinates global construct a simple Lithium lens This element consists of a current carrying cylinder and its field The field exists only between the end planes of the cylinder out to adial infinity Named Arguments radius The radius of the current carrying cylinder 5 mm length The length of the cylinder 100 mm current The current in the cylinder 100000 Amp material The material of the cylinder Li color The color of the tube or cylinder invisible maxStep The maximum stepsize in the element mm provides interactive list of interesting internal tables list with no arguments lists all lists except processes list name lists that specific one list exit name s will exit after listing List names are commands all commands materials currently known materials physics a physics lists
11. invisible Implement a cornerarc in the centerline The centerline is bent by a rotation Thr corners are used to approximate an arc the total angle and path length are equal to those for the arc Should be used immediately after an idealsectorbend or a genericbend The z value is for the front face of the arc NOTE This command is self placing do not use the place command it also affects all following placements and it cannot be issued inside a group This command is well matched to a sector bend but can also be used with a normal bending magnet normally the magnet is placed before the cornerarc and is rotated by half the bend angle The only useful rotations are those around the centerline Z z angle and centerRadius are required parameters NOTE all placements before this command must have z values before the corner and all placements after this command must have z values after the corner Note also that the angle is limited to 90 degrees Note that the radiusCut is important to reduce or eliminate ambiguities in the global to centerline coordinate transform It can also be used to shield the beamline to prevent particles from taking unusual paths around the outside of beamlin elements Named Arguments Z The centerline Z of the cornerarc mm centerRadius The radius of the centerline arc mm angle The angle of bend gt 0 left lt 0 right degrees
12. mm mm mm maximum stepsize in the element material of the box color of the box invisible mm nonzero to kill every track that enters G4beamline User s Guide 49 bug1021 coil 1 10 14 TJR Workaround to improve accuracy of bug When a charged particle turns around wildly incorrect kinetic energy distance to turn around until minStep is reached Simulations in which there are no E f particl ver gets below 0 001 MeV i to apply this workaround Named Arguments minStep Minimum step in space defines a coil part of a solenoid A coil is a geometrical tube that can a solenoid The field is computed for infinitely thin current sheets evenly solenoid specifies the actual current computation is too slow computed and written to filename mm 1021 in E field in an E field ields n an E a bug in the Geant4 transportation process can sometimes give it a This workaround computes the and limits the step to half that vlue at that point the track is reflected or no charged field have no need default 0 002 carry current when part of a set of nSheets spread radially For tracking the so a field map on a grid in r and z is defaults to coilname dat The While there are lots of parameters specifying the field map it is recommended to simply accept innerRadius toleranc Th outerRadius length mat the defaul
13. substitutions 0 MacroName 1 S 9 Positional arguments of the command S macro expansions for generating unique names NOTE Sparamname is expanded in the define command but SSparamname is expanded when the macro is invoked demo command This demo command takes both positional and named args and is the prototype class for all commands All argument values are merely displayed demo default name value sets default values Named Arguments sl a demo string argument s2 a demo string argument dl a demo double argument d2 a demo double argument Construct a Detector that generates an NTuple A Detector generates an NTuple of tracks when they enter th physical volume of the Detector summing up the total energy deposited until it leaves the volume By default an entry in the NTuple is generated for each event with the track variables set by the first track as it enters the detector Set perTrack 1 to generate an entry for each track A detector may be placed via multiple place commands usually with a rename det argument to distinguish the different placements Each placement creates an individual NTuple If material is not specified it uses Scintillator For a circular Detector give radius for a rectangular one give height and width length is always needed G4beamline User s Guide 53 by The NTuple by default uses local coordinates The NTuple of
14. torus totalenergy 1 10 14 TJR Bx By Bz Ex Ey Ez ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Tesla Megavolts meter Valid Formats ignore case ascii bltrackfile dummy for009 for009 dat root trackfile Extended asciiExtended rootExtended Named Arguments cannot be changed in place cmd time The global time of the sampling ns format The NTuple format see above for list filename The filename of the NTuple file Synonym for filename require Expression which must be nonzero to include the track default 1 coordinates Coordinates global centerline or reference default c referenceParticle Set to 1 to include the Reference Particle construct a torus This is a direct interface to G4Torus The major radius is in the X Y plane with phi 0 along X Named Arguments innerRadius The inner radius of the torus mm outerRadius The outer radius of the torus mm majorRadius The major radius of the torus mm initialPhi The initial phi around major radius 0 degrees finalPhi The final phi around major radius 360 degrees maxStep The maximum stepsize in the element mm material The material of the torus color The color of the torus invisible kill Set nonzero to kill eve
15. uses iven modeling for the reactions of energetic ons and nucleons It employs quark gluon string the punch through interactions of the e with a nucleus the string excitation tions being calculated in quasi eikonal tion A pre equilibrium decay model with an evaporation phase to model the behavior of the after the punch It uses current best pion tion GSP but using Geant4 Bertini cascade for primary neutrons pions and Kaons below 10GeV In n to experimental data we find improved agreement ompared to QGSP which uses the low energy ised LEP model for all particles at these nergies neutrons agreement QGSP_BERT CHIPS QGSP_BERT_ HP Lik QGSP_BIC Like QG protons a replacing neutrons better d Gl GI The Bertini model produces more secondary and protons than the LEP model yielding a better to experimental data No synopsis available e QGSP_ BERT but with _HP modeling for neutrons SP but using Geant4 Binary cascade for primary nd neutrons with energies below 10GeV thus the use of the LEP model for protons and In comparison to teh LEP model Binary cascade produced nuclei QGSP_BIC_HP Like QGSP_FTFP BERT N QGS_BIC No synop QGSP_INCLXX No s Shielding No syn Defines a pillbo A Pillbox RF cav linac The phase at the center of is determined fr tracked through zero crossing of used rather than The Pipe walls wall collar wi th
16. Arguments are of the form name 1 1 0 where name is the name of a material and 1 1 0 is the R G B value desired for its color for invisible Set hideOthers 1 to make all other materials invisible BEWARE Vacuum and vacuum are different materials as are Iron and Fe defines a solenoid a coil and current A solenoid is a coil and a current If alternate is nonzero then each placement of the solenoid or an enclosing group will flip the sign of current Named Arguments cannot be changed in place cmd coilName The name of the coil must exist current The current density in the conductor Amp mm 2 color The color of the solenoid invisible alternate Set nonzero to alternate sign each placement kill Set nonzero to kill all tracks that hit the coil coil Synonym for coilName Beam frame Green s function space charge computation This is a space charge computation for bunched beams It uses a grid in the beam frame to solve Poisson s equation via a Green s function with infinite boundary conditions the E field is boosted back to the lab frame E and B for tracking Macro particles are used to enable the simulation of larger bunches than can be feasibly simulated as individual particles the macro particles have zero radius but are pro rated into the nearest eight grid points when placed into the grid This computation can handle up to about a million macro par
17. Outside the grid an approximation is used An approximation grid is constructed with the same size of the Poisson grid but using nxApprox nyApprox nzApprox points Particles are placed into this approximation grid and the mean position is kept as well as the charge Approximation grid points with less than 1 of the total charge are consolidated with their inner neighbors The non zero approximation grid points are treated as point charges when computing the potential outside the grid For reasonably Gaussian bunches 7 7 7 are reasonable values for the approximation grid sizes The E field in the beam frame is computed via the derivatives of the linear interpolating function using the eight nearest grid points and is boosted back to the lab frame E and B for tracking by the usual Geant4 routines Bunch particles that get destroyed cease contributing to the bunch As the bunch particles are selected during start up no additional particles ar ver added to a bunch This algorithm handles multiple bunches of any particle types NOTE For now the reference MUST be parallel to the Z axis Named Arguments deltaT Time step ns charge Charge of macro particles times particle charge nx Number of grid points in x 65 ny Number of grid points in y 65 nz Number of grid points in z 65 dx Max distance of particle to reference in x mm dy Max distance of particle to
18. cornerarc Implement a cornerarc in the centerline start Define the initial start of centerline coordinates Beam definition commands beam Define the Beam cosmicraybeam Define a Cosmic Ray muon beam particlesource Interface to the Geant4 General Particle Source reference Define a reference particle Auxiliary definition commands material construct a new material particlecolor Set the colors for particle tracks trackcolor Alias for particlecolor Beamline element definition commands absorber construct an absorber boolean Construct an element from a boolean operation between elements box construct a box coil defines a coil part of a solenoid cylinder Alias for tubs extrusion construct a solid extrusion with axis along z fieldexpr implements a field map E and or B from expressions fieldmap implements a field map E and or B from a file genericbend construct a generic bending magnet genericquad construct a generic quadrupole magnet helicaldipole construct a helicaldipole magnet helicalharmonic construct a helicalharmonic magnet idealsectorbend construct an ideal sector bending magnet lilens construct a simple Lithium lens multipole construct a generic multipole magnet 1 10 14 TJR G4beamline User s Guide 43 particlefilter Will kill particles from a list or force particles to decay pillbox Defines a pillbox RF cavity polycone construct a polycone with axis along z rfdevice Define
19. rotation The rotation of the cornerarc see above radiusCut The radius cut for this following segment mm cosmicraybeam Define a Cosmic Ray muon beam 1 10 14 TJR The muon beam is nominally headed in the Z direction implying that Z is physically DOWN The beam intersects a box defined by beamWidth beamHeight and beamLength centered at X Y 0 and beamZ For each event a point is selected randomly within this box angles theta and phi and the muon momentum are generated according to a fit to their sea level distributions the track is extended backwards to the celestial sphere and that is the initial beam position for the event The muon flux through the G4beamline User s Guide 52 cylinder define demo detector 1 10 14 TJR rectangle at Z beamZ is used to display an estimate of the sea level exposure time for the run Named Arguments nEvents Number of events to process beamZ Beam location in Z mm radius Radius of celestial sphere mm beamHeight Rectangular Beam height mm beamWidth Rectangular Beam width mm beamLength Rectangular Beam length mm Alias for tubs defines a macro argument expanded set of commands The first argument is the macro name additional arguments become lines in the body of the expanded macro The macro name becomes a command with up to 9 positional arguments When the command is issued the body is expanded and executed with these
20. s Guide 95 trap tube tubs 1 10 14 TJR NOTE the trackerplane s of a tracker MUST be placed in the order that particles will hit them the code does not sort them Usually this means that each place command of a trackerplane must have a larger z value than the previous place command They must also come after the trackerZ value of the tracker command Named Arguments tracker The tracker to which this plane belongs REQUIRED radius The radius of the circular tracker plane mm innerRadius The inner radius of the circular tracker plane 0 mm height The height of the rectangular tracker plane mm width The width of the rectangular tracker plane mm length The length of the tracker plane mm theta Wire angle in X Y plane deg 0 gt x 90 gt y wireSpacing Wire spacing mm wireOffset Wire 0 offset mm errType Error type fixed gaussian rect errTheta Error in wire angle deg errSpacing Error in wire spacing mm errOffset Error in wire offset mm sigmaTime Sigma for timing plane ns default 1 maxStep The maximum stepsize in the element mm g material color The material of the tracker plane The color of the tracker plane invisible A construct a solid trapezoid with axis along z This is a direct interface to G4Trap The trapezoid is symmetrical left right but upper or lower width can be larger or smaller N
21. NER File Etc Help Motion X Motion Y E D Oo amm Motion Z doublecellAssembly The macro may be used as H lt z mm gt lt Pout MeV c gt lt maxGradient MV m gt doublecellAssembly 1000 250 0 23 09 Another macro describing a superconducting solenoid its field map counterwound conductors and iron shield may also be defined solenoidAssembly lt z mm gt lt current A gt solenoidAssembly 500 LeS Both macros as well as a couple predefined tubs section 5 77 may be placed inside yet another macro that constructs a whole cryomodule SI 2 3 4 1 10 14 TJR G4beamline User s Guide 168 middleCryomodule lt z mm gt lt current A gt lt Pout MeV c gt lt maxGradient MV m gt define middleCryomodule place beamPipe z 1 zo miPipe length LmiPipe S cl rename miPipe solenoidAssembly 1 zo misolenoid 2 SO N doublecellAssembly 1 zo midoublecell 3 S4 place beamPipe z 1 zo mivaPipe length SLmivaPipe cl rename mivaPipe place valveAssembly z 1 zo mivalve Note that macros are invoked while objects are placed For example to put this cryomodule off the Z axis one would need to modify the macro that defines the cryomodule to pass the x and y parameters to each of the individual place commands within each macro Also note that when using field maps the current and maxGradient quantities multiply the quantities within
22. Oo 0 0 O O lace Box z 0 rename Beam color 0 1 0 lace Quad z 2000 rename Q1 gradient SQF lace Quad z 3000 rename Q2 gradient SQD lace Quad z 4000 rename Q3 gradient SQF lace Box z 10000 rename End color 1 0 0 profile file profile txt partic le mut zloop 0 01 10000 100 1 10 14 TJR G4beamline User s Guide 115 6 10 SampleMovie g4bl SampleMovie g4bl Just like Examplel g4bl but with movie command added Simpl xample g4beamline input file a 200 MeV mut Gaussian beam is tracked through 1l meter drift spaces into four detectors movie QGSP is the default physics use case for High Energy Physics but QGSP BERT is better for low energy simulations physics QGSP_ BERT the beam is nominally headed in the Z direction beam gaussian particle mut nEvents 1000 beamZ 0 0 sigmaX 10 0 sigmaY 10 0 sigmaXp 0 100 sigmaYp 0 100 meanMomentum 200 0 sigmaP 4 0 meanT 0 0 sigmaT 0 0 a reference particle reference particle mut referenceMomentum 200 BeamVis just shows where the beam comes from box BeamVis width 100 0 height 100 0 length 0 1 material Vacuum color 1 0 0 place BeamVis z 0 define the detector virtualdetector Det radius 1000 0 color 0 1 0 place four detectors putting their number into their names lace Det z 1000 0 rename Det lace Det z 2000 0 rename Det lace Det z 3000 0 rename Det lace Det z 4000 0 rename Det Pl pl Ppl P
23. a pattern that matches its name in the detectors the ntuple command Note that includes rename not the name given to this command noSingles argument may be useful in this case to avoid a NTuple of singles an empty NTuple may be created argument to must match the name as placed The Lees huge Note that secondary particles created within the virtualdetector will not get an entry until they have taken one step They ar guaranteed to do so The standard NTuple fields are X Y Z mm Px Py Pz MeV c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 The following additional fields are appended for format format asciiExtended and format rootExtended Bx By Bz Tesla Ex Ey Ez Megavolts meter ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Valid Formats ignore case Extended ascii bltrackfile dummy for009 for009 dat root trackfile Extended asciiExtended rootExtended Named Arguments cannot be changed in place cmd radius The radius of the circular VirtualDetector mm innerRadius The inner radius of the circular VirtualDetector 0 mm solid height The height of the rectangu
24. and sigmaYp are determined empirically to be larger than the actual beamline acceptanc SH HEHE H 1 10 14 TJR G4beamline User s Guide 107 In the beam command sigma lt 0O means a flat distribution with that halfwidth beam gaussian sigmaX 2 57 sigmaY 1 0 meanMomentum SpiMomentumRef particle pi sigmaXp 0 040 sigmaYp 0 020 sigmaP 17 firstEvent Sfirst lastEvent Slast amline magnets and components EH define the b EH virtualdetector 1 TargetDet radius 100 length 1 material Vacuum noSingles 1 genericquad QuadTypeIV fieldLength 853 4 apertureRadius 101 5 ironRadius 381 ironLength 914 ironColor 0 6 0 kill 1 Type I bend shimmed to 200 mm gap genericbend BendTypeI fieldWidth 660 fieldHeight 200 fieldLength 1038 ironColor 1 0 0 ironWidth 1828 ironHeight 1320 ironLength 990 PSI solenoid coil Decay innerRadius 60 0 outerRadius 97 0 length 5000 0 maxR 60 0 mapFile Magnets DecaySolenoid solenoid DecayS coilName Decay current SDecaySolenoidCurrent color 1 1 0 color 1 1 0 color 1 1 0 invisible shiel tubs SolenoidBody innerRadius 97 0 outerRadius 180 length 5000 kill 1 tubs DecayEnd innerRadius 48 outerRadius 180 length 68 material Fe kill 1 d to kill junk from B1 that misses the apertur tubs DecayShield color invisib innerRadius 180 outerRadius 1000 length 2 kill 1 e the assempled DecaySolenoid group DecaySolenoid
25. argument to the command line 2 13 Event Time Limit Every event is subject to a per event time limit This is controlled by the parameter eventTimeLimit which defaults to 30 seconds but can be set by the param command As long as the program is taking physics steps this time limit will cause the current event to be killed and the next event to be simulated restarting the time limit In case the code gets into an infinite loop an alarm is set at the start of each event for eventTimeLimit 10 and if this fires the entire program will be aborted recovery is not possible this prevents it from exhausting your CPU allocation on a cluster Note that systems with stable particles and electromagnetic traps can run literally forever You may not think your system has this property but low energy delta rays e can surprise you Note also that putting a medium or high energy electron or photon into a block of material can generate many thousands of secondaries which can take a very long time to track A different type of time limit is implemented via the maxTime argument to the trackcuts command it is a limit on the global time in the simulated world 2 14Wall Clock Limit An additional processing limit is determined by the parameter wal ClockLimit It defaults to 1 indicting an infinite time limit Setting it to a positive value will limit the run time to that many seconds This is most useful on a supercomputer where jobs are limited by
26. gammaToMuPair Nonzero to add gamma gt mut mu 0 spi syn syn max Fur The LHE FTF QGS QGS a E mE a w w M _HP Lis CHI FTF NO nTracking Nonzero to track particle spins 0 chrotronRadiation Nonzero to add synchrotron radiation to the physics list for e and et chrotronRadiationMuon Nonzero to add synchrotron radiation to the physics list for mu and mu NOTE This is experimental and may not work correctly Time Maximum time for tracking 1000000ns PAY OLES DESTO SRE FS ther guidance in selecting physics lists is available at ea Zo 5 a default all around physics list for HEP is called FTFP B P uses exclusively parameterized modeling lists use the FRITIOF description of string excitation and fragmentation P lists use the quark gluon string model C are as QGSP except applying CHIPS modeling for the nuclear de excitation ERT uses Geant4 Bertini cascade below 10 GeV C uses Geant4 Binary cascade below 10 GeV MV suffix indicates a faster but less accurate EM modeling X suffix indicates the low energy EM processes suffix uses the data driven high precision neutron package thermal to 20 MeV E suffix indicates a list for comparison with earlier releas t of available physics lists PS No synopsis available P BERT For calorimetry The FTF model is based on the FRITIOF description of st
27. outerRadius The outer radius of the sphere mm initialPhi The initial Phi value deg 0 for all finalPhi The final Phi value deg 360 for all initialTheta The initialTheta of the sphere deg 0 for all finalTheta The finalTheta of the sphere deg 180 for all maxStep The maximum stepsize in the element mm material The material of the sphere color The color of the spher invisible kill Set nonzero to kill every track that enters Define the initial start of centerline coordinates If used this command must come before any other command that puts an element into the world or affects the centerline coordinates place beam corner cornerarc and reference commands This command may not always be needed but it is needed to eliminate the ambiguities in the global to centerline coordinate transform and when simulating a ring to ensure that sensible values of the centerline coordinates are used Note that the radiusCut is important to reduce or eliminate ambiguities in the global to centerline coordinate transform It can also be used to shield the beamline to prevent particles from taking unusual paths around the outside of beamlin elements Named Arguments x The global x position of the start y The global y position of the start Z The global z position of the start initialz The initial centerline z value rotation The initial rotation of the centerline radiusCut The radius cut
28. that makes it difficult to update G4beamline similarly the G4beamlineExamples directory is not a good place to work except to run the examples It is usually a good idea to work in your HOME directory and to make a separate directory for each simulation this is especially true if you are using the GUI I have a single directory in my HOME called g4work under which I create a new directory for each new simulation using a descriptive name 7 6 Files Common to Multiple Simulations Many G4beamline commands reference additional files In some cases there will be a collection of different simulations that share common files such as field maps window profiles etc It may be convenient to put these files into a single directory called Common at the same level as the simulation directories Then in each input file reference these common files as Common filename ext 7 7 Basic Execution in a Command Line Environment Most modern desktop environments permit the user to have multiple command line windows open simultaneously This can significantly improve your productivity while developing a new G4beamline simulation or optimizing parameters of an existing one Multiple windows are not necessary and what I describe in parallel can be performed sequentially in a single command line window it is noticeably more efficient with multiple windows however Usually when developing a new simulation or optimizing the parameters or config
29. ultiply multiple scattering and energy loss by factors The multiple scattering and ionization energy loss processes are not really independent the msc factor applies to scattering in both and the eLoss factor applies to the fluctuations of energy loss in both The mean energy loss is not affected note that in some EM models including the one used for muons the fluctuations only increase the loss from the mean so the average energy loss is affected but only slightly The deltaRay parameter is the probability of keeping any given delta ray The 3 momentum of each discarded delta ray is added back into the particle s 3 momentum and its K E is recomputed Note that with msc 0 tracks can still be scattered if deltaRay gt 0 This command applies ONLY to multiple scattering and ionization energy loss Other processes still apply which can scatter and cause a reduction of the track s energy For muons you may wish to disable these processes in the physics command muBrems muPairProd CoulombScat Decay similarly for other particles Problems may occur if any factor is gt 1 0 in particular the position may be wrong it might even cross a volume boundary illegally causing major tracking errors code is optimized for 0 0 lt msc eLoss DeltaRay lt 1 0 Named Arguments particle Comma separated list of particle names or patterns default none msc Ratio for multiple scatt
30. 2 RMS 279 7 leet 500 0 500 1000 1500 The way to find this event is to use a slider and the EventID features in historoot to select the outlier event and write a histo_events txt file X HistoRoot Use the File menu to open file s select an NTuple and Plot type then enter expressions below g4beamline root VirtualDetector Deti 1000 entries g4beamline root VirtualDetector Det2 1000 entries g4beamline root VirtualDetector Det3 1000 entries g4beamline root VirtualDetector Det4 1000 entries Plot Type 1d Histogram C 2d Histogram scatter plot C X Plot Ptot KEproton KEmuon KEalpha x y z Px Py Pz t PDGid EventID TrackID ParentID Weight I errorbars sqrt sum of weights squared Enter expressions below using the fields of the NTuple listed on left and C arithmetic functions and operators A right click will insert from the list of fields of the NTuple x fx y weight errorbar X errorbar Y The sliders below impose range cuts on the NTuple Ix See the Help for explanations of the following fields Max Events Bericlelyned EventiDye venti Create Plot 1 10 14 TJR Note that slider S1 has the same expression as the histogram x this permits you to use S1 to select just the outlier event As the EventID field contains an expression that evaluates to the event of the NTuple G4beamline User s Guide row his
31. 5 ranks as rank 0 needs only a few percent of a core On a supercomputer using dozens or hundreds of cores rank 0 should have its own core By default MPI message passing does not block in order to reduce message latency This means that rank 0 will use 100 of a core even though it does very little processing On a supercomputer with hundreds of ranks working that is appropriate but it is wasteful on a small computer with just a handful of cores Setting MPI IdleSleep 1 will make rank 0 sleep for 1 millisecond when it is idle i e is not processing a message from a worker On a 4 core computer running 5 ranks this can improve throughput by about 20 Larger values only reduce throughput There is little point in changing either MPI_PackTracks or MPI_PackNTuples larger values do not help and smaller values only reduce throughput The parallel performance of G4beamline on your simulation will depend on a the speed of the CPUs b the speed and latency of the network among them and c the size of the system being simulated See section 8 5 2 below Some aspects of G4beamline have their operation modified in MPI mode steppingVerbose 1 Performed independently on each rank writing to files rank out unless MPI WorkerOutput 0 fieldntuple Performed only in rank 1 to avoid duplication These printfield commands are not normally used in MPI mode as they are probefield primarily for debugging tr
32. B2 reference referenceMomentum muMomentumRef particle mu beamZ 12164 7 place ProtonAbsorber z 15070 9 place BendTypelI rename B2 By B2 z B2z x 100 rotation Y15 fieldMaterial Air cornerarce z 15281 7 angle 30 centerRadius 2005 2 place Collimator z 16760 x 353 place Collimator z 16760 x 353 place QuadTypeQC rename 04 gradient SQ04 z 17361 6 fieldMaterial Air 1 10 14 TJR G4beamline User s Guide 109 place QuadTypeQC rename Q5 gradient SQ5 z 18521 6 fieldMaterial Air ironColor 0 0 6 place QuadTypeQC rename Q6 gradient SQ6 z 19681 6 fieldMaterial Air place QuadTypeQC rename Q7 gradient SQ7 z 22993 7 fieldMaterial Air place QuadTypeQC rename Q8 gradient SQ8 z 24153 7 fieldMaterial Air ironColor 0 0 6 place QuadTypeQC rename Q9 gradient SQ9 z 25313 7 fieldMaterial Air place Diffuser z 27165 3 place DiffuserDet NOTE the entire cooling channel has moved upstream End coil 1 1 upstream face is now z 27169 1 Define and place the MICE upstream particleID elements material scintillator density 1 032 C 0 918 H 0 082 virtualdetector TOFO height 500 width 500 length 50 8 color 1 1 1 material scintillator virtualdetector TOF1 height 480 width 480 length 50 8 color 1 1 1 material scintillator place TOFO z 20537 0 TOF1 and TOF2 are placed with the cooling channel material F Z 9 A 18 998 density 1 5 material C6F14 de
33. COM BRAIN IC CADMIUM CARBON T CELLULOS CALCIUM ULFATE BE PACT ICR RP BUTANI TUNGSTAT zj Z WN Ow Z Z m m E BERYLLIUM OXIDE _CORTICAL ICRP BO BUTYL ALCOHOL C 552 CALCIUM CARBONATE OXIDE CALCIUM SULFATE ETRACHLORIDE CELLULOSE RON CARBI AAG CALCIUM CALCIUM T CELLOPHANE CELLUL FL UNGSTATE BGO BLOOD IC CADMIUM UORIDE BON DIOXID B R DE B TELL P O U RON OXID RIDI J CAR OSE ry ry ESIUM FLUORIDE CHLOROBE CESI E NITRATE CERIC SULFATE NZENE CHLOROFORM CONCRI CYCLOHEXANE DICHLO RODIET HYL ETHER 1 2 DIC ETHANE DI N N DIME HYL CE ea 1 2 DIC m l H UTYRATE UM IODIDI HLOROB CI GI GI ENZE ER ETHYL ETHANE THYL FORMAMIDE DIMETH el 3 THYL ALCO HOL O F H YL L Cl EI LLULOSE ETHYLENE EYE ICRP FERRIC OX EON 13 PHOT UTAMIN THANU UM UM ESI MAGN MS20 TI MUSCLE NITROB m E gt v A ra B a a Et EN RROUS OXIDE F U ESIU S R SULFOXID S ER REON 12B DE GALL FERROUS_SULFATE EON 13I1 GADOLIN ION Pyrex Glas RI Bl OQ EMULS EAD GLASS IDE ERROBO 2 F IUM PLAT kal D m j O N 13 RSENIDE GLUCOS Eal ROL GUAN
34. G4beamline 2 14 mpi G4beamline 2 14 source configure enable mpi disable visual make Note the export of variables CC and CXX to prevent the Makefile from using the defaults which are an old version of gcc and g which you do NOT want to use MPI is already known by the compiler Be sure to do module load PrgEnv gnu in your batch script to gsub it is needed to find shared objects On Hopper use the default MPI_IdleSleep 0 NOTE Hopper does not have a very good method of detecting when memory is exhausted on a worker node even though G4beamline itself does You really want to avoid running out of memory as Hopper does not permit the job to closeup gracefully and all results will probably be lost The message OOM killer terminated this process indicates the job was killed due to a worker node being Out Of Memory If you are part of a project that uses G4beamline there may already be an installation of G4beamline for your project For the Muon Accelerator Program MAP look in project projectdirs map Codes Here is an example script for submission via gsub PBS q debug PBS 1 mppwidth 24 PBS 1l walltime 00 30 00 PBS N Benchmark PBS j eo source project projectdirs map bin compiler gnu source project projectdirs map Codes G4beamline bin g4bl setup sh cd PBS_O WORKDIR g4blmpi 24 Benchmarkl1 g4bl wallClockLimit 240 These parallelization plots were made on hopper nersc gov using the scripts in the B
35. It will also place a copy of the G4beamlineExamples and the G4beamlineDocumentation into My Documents G4beamline Examples Delete the downloaded file after installing it To use the command line programs you must a install the Cygwin environment b use its bash shell and c add the G4beamline programs into your PATH source C Program Files MuonsInc G4beamline bin g4bl setup sh You may put this into your HOME bash_ profile There is a similar g4b setup csh 1 10 14 TJR G4beamline User s Guide 6 The first time you run G4beamline it will launch a helper program G4bIData to download the required Geant4 data files 1 1 1 2 Linux Intel Prerequisites e Java SE Runtime Environment 1 5 or later http java sun com if you have the JDK installed that includes the runtime environment e Root 1 24 or later http root cern ch Root is not required if you will use only ASCII output files though you probably will find the HistoRoot program useful to generate plots of Root and ASCII files and it requires a specific version of Root The distribution file is G4beamline VERSION Linux tgz available from http g4beamline muonsinc com Simply download it and un tar it in your HOME tar xzf g4beamline VERSION Linux tgz Delete the downloaded file after doing this This will construct an icon on your Desktop to run G4beamline g4beamline VERSION Linux bin g4bl icon You can copy this icon into any men
36. Tesla ximum stepsize in the element mm terial of the field region lor of the field region terial of the iron region lor of the iron region nzero to kill particles hitting the iron field computation set to 0 to disable or a separated list of 6 Enge function parameters depth factor 1 0 nzero to omit the aperture volume genericquad construct a generic quadrupole magnet The field region is a tubs with gradient specified A positive gradient yields a horizontally focusing quad for positive particles If apertureRadius gt 0 the quad has a circular aperture For bugs in th a rounded ap poleTipRadius coilR latter rture using circles for the poles set adius coilHalfwidth Due to visualization case you cannot see through the aperture it is solid black A fringe field computation based on the method of COSY INFINITY is included by default extending the field region This is first order only and the fringe field extends outside of th rtur magnet ap straight along local it is slightly non Maxwellian It is computed using Enge functions only in a cylinder extending the aperture z As the fringe field is first order only Note that there is no field inside the iron this can result in gross tracking errors for particles in the iron and implies that kil 1 1 is des irable If ironLength lt 0 Named Ar
37. The new g4blmovie command has one argument an input file to describe the movie This gives great flexibility in organizing the picture as a number of panes each displaying a pair of expressions using the track variables The panes are laid out in rows with no inherent limit on either the number of panes in a row or on the number of rows but too many of either will probably make the movie unwatchable The input file is quite similar to that of G4beamline except that quoted arguments are not allowed spaces are not permitted or needed in any argument and there are no parameters g4blmovie input file commands Command Argument Description setup This command must be first It sets basic parameters for the movie outputFile The output movie file Its extension determines the format any format supported by ffmpeg can be used The following extensions are known to work mov swf avi Beware spaces are not allowed windowWidth The movie window width in pixels All panes scale to this value windowHeight The movie window height in pixels All panes scale to this value tMin The simulation s start time of the movie ns tMax The simulation s end time of the movie ns duration The real time duration of the movie in seconds 10 frameRate The frame rate of the movie frames sec 24 textHeight The default height of text in pixels 15 Changeable in other commands background The ba
38. apertureRadius nonzero the latter is controlled by the parameters shown in the figure Note the rounded aperture uses circles to approximate the poles real magnet poles are between hyperbola and circle to compensate for proximity to the neighboring pole and the coil ironRadius ironRadius coilHalfwidth poleTipRadius apertureRadius coilRadius 4 8 G4beamline Commands by Type This section is just the output of the help command with a little re formatting The help command help provides interactive help 1 10 14 TJR G4beamline User s Guide 42 man Alias for help Program control commands define defines a macro argument expanded set of commands do Do loop endgroup ends a group definition exit exit a command file for For loop g4ui Accesses the Geant4 user interface geometry Arranges to perform a geometry test group begins definition of a group if Conditional execution of command s and if elseif else endif include includes a command file list provides interactive list of interesting internal tables output redirects stdout and stderr to a file param Defines parameter values randomseed control pseudo random number generator seeds showmaterial Set the colors for selected materials trackermode Sets mode for all trackers manages track fitting tune Tune a variable used as argument to other elements Centerline layout commands corner Implement a corner in the centerline
39. by extendX flip Bx Ex and the field flips will be the products of both commands cylinder maps are a 2 D map with rotational symmetry around the Z axis Each field component has a single block with lines being Z and the columns being R The cylinder command has the following arguments ZO The Z value for the first line in each block nR The number of columns per line nz The number of lines per block dR The R increment between colums dz The Z increment between lines tolerance The tolerance for pointwise data default 0 01 mm After the cylinder command the following optional commands can be given extendZ flip This command behaves the same as for the grid map After the commands each block consists of a line containing the name of the field component followed by the lines of the block The values within a line can be separated by whitespace or a followed by optional whitespace Field components that are not given are set to 0 0 everywhere Missing values will be considered to be 0 0 For grid maps the first block is for Z Z0 and successive blocks FF F F FF F FF F FF F F FF FF F FF FF F FF FF F FF F FF F F F FF F FF FF F FF F F F FF F F F FF F FF FF FF F F FF F F KF OF 1 10 14 TJR G4beamline User s Guide 173 FF F FF F F F FF F F FF F FF F FF F FF F F F FF F FF F FF F FF FF FF F FF FF F FF F FF F F FF F FF FF F F FF F F KF OF inc
40. c construct a polycone with axis along z This is a direct interface to G4Polycone For a solid polycone omit innerRadius and it will be filled with zeroes The number of entries in z innerRadius and outerRadius must be the same Not that a polycone is placed at its z 0 r 0 point which need not be its geometric center Named Arguments cannot be changed in place cmd G4beamline User s Guide 78 innerRadius Comma separated list of inner radii mm outerRadius Comma separated list of outer radii mm Z Comma separated list of z positions mm initialPhi The initial Phi value deg 0 for all finalPhi The final Phi value deg 360 for all maxStep The maximum stepsize in the element mm material The material of the polycone color The color of the polycone invisible kill Set nonzero to kill every track that enters printf prints track variables and expressions This is an interface to the C printf function The first positional argument is the format and the following positional arguments are double expressions printed with the fields in the format Up to 16 expressions can be printed The print is performed only if the required expression is nonzero as each track reaches one of the Z positions in the z argument centerline coordinates Multiple printf commands with the same file will be combined into the file as tracks reach any of their Z positions More th
41. c MeV c MeV c ns OR mm mm mm MeV c MeV c MeV c ns When writing mm are used on reading mm are assumed but a comment line containing cm cm cm switches to cm Thereafter follow the tracks one per line While the input routine can handle initial spaces in the first column it is STRONGLY suggested you not put any there so cut grep will work Any fixed or floating point format will do PDGid EV TrkId and Parent are integers but 00 can be appended FF F F F F F F FF F FF F FF F FF F FF F FF F OF Common PDGid s e Jal e 11 mu 13 mu 13 pi 211 pi 211 proton 2212 nti pr ton 2212 neutron 2112 anti_neutron 2112 gamma 22 9 2 Trace File When writing track traces with format ascii in the trace command the output is as follows The first 12 columns are identical to those of BLTrackFile Columns 13 14 15 give Bx By Bz in Tesla Columns 16 17 18 vive Ex Ey Ez in MegaVolts meter The first 3 comment lines are similar to those of BLTrackFile giving a comment the column names and their units All values are in the selected coordinates from the trace command centerline global or reference 9 3 FOR009 DAT NOTE Because the FOR009 DAT format requires the particles be sorted by region JSRG all tracks are stored in memory until close is called the file is written at that time The ICOOL region is determined from the Z position of the
42. decapole T m 4 dodecapole Strength of dodecapole T m 5 ironColor The color of the iron region kill Set nonzero to kill tracks hitting the iron maxStep The maximum stepsize in the element mm fringe Fringe field computation set to 0 to disable fringeFactor Fringe depth factor 1 0 openApertur Set nonzero to omit the aperture volume muminuscapturefix Fixes up the G4MuonMinusCaptureAtRest process 1 10 14 TJR This class adds extra neutrons to mu capture The neutrons are added with a Poisson distribution having a mean of neutronMeanNumber and with an exponential distribution in kinetic energy 1 neutronMeanEnergy exp KE neutronMeanEnergy As the muonic atom cascades to its ground state it forgets the incident mu direction so the extra neutrons are generated isotropically in the lab G4beamline User s Guide 68 The extra neutrons are added only to those captures that are hadronic i e not decay in orbit The value of neutronMeanNumber should reflect this The default values correspond to Aluminum Named Arguments neutronMeanNumber Mean mumber of extra neutrons per nuclear capture 2 5 neutronMeanEnergy Mean energy of neutron spectrum MeV newparticlentuple NTuple containing particle tracks when created ntuple 1 10 14 TJR Note that initial beam particles are included unless require is set to ParentID gt 0 The standard NTuple fields are X Y Z mm Px Py Pz Me
43. directory and type any input file will do g4bl Examplel g4bl viewer best Once the viewer opens its window you will get an Jdle gt prompt to which you can reply help lt CR gt and obtain help on any Geant4 UI command Note there are lots of options for the Geant4 viewers and this is only a short list of those that users have requested in the past If there is some aspect of drawing that you want chances are fairly good that it is available 2 8 1 1 Different Drawing Scales Many beamlines are much longer than they are wide or tall This makes the transverse dimensions difficult to see in a viewer and when magnification is increased to see them only a very small portion of the beamline is visible at a time This can be addressed by using different drawing scales for x y and z The command to scale x by 2 y by 3 and z by 4 is g4ui when 4 vis viewer scaleTo 2 3 4 Or type vis viewer scaleTo 2 3 4 to the idle gt prompt 2 8 1 2 Changing the Background Color To set the background color to white use this command 1 10 14 TJR G4beamline User s Guide 20 g4ui when 4 vis viewer set background 1 1 1 The 3 values are for red green and blue and should each be a value between 0 and 1 black is 0 0 0 the default A fourth value for opacity can be given 2 8 1 3 Drawing Axes Drawing the coordinate axes can make it easier to find your way around the image of the system in a viewer You can draw a set
44. energy loss 1 10 14 TJR G4beamline User s Guide 32 3 3 Electromagnetic Field Map Tolerance Several elements that implement electromagnetic fields internally construct a field map because evaluating the field during tracking is too CPU intensive These are coil and fieldexpr They each have a tolerance argument that is used to determine the required grid spacing of the map Its value obviously affects the accuracy of the simulation This is of course also true for externally supplied EM field maps 3 4 Secondary Creation Threshold in Physics Processes An important trade off between physics accuracy and CPU time in Geant4 is the production of low energy delta rays e and other particles which diverge at low energies The approach is to only generate a secondary when the range of the particle in the current material exceeds a user specified minimum range cut which is converted to a kinetic energy threshold for each material Particles with shorter ranges are not produced as secondaries but are lumped into the continuous ionization energy loss in the material In G4beamline this is set by the minRangeCut argument to the physics command its default value is 1 mm If your simulation has objects smaller than that or you are working at scales much larger than that you should consider changing its value unless you just don t care about these low energy particles 3 5 Track Cuts The trackcuts command applies cuts to every track both b
45. for the initial segment mm ring Set nonzero to indicate a ring is present survey command The survey command writes the coordinates of the front and rear points of each element to a file stdout if For most elements the points written are the geometrical centers of their front and rear faces Elements are all objects put into the world via the place command Entries are sorted by Zfront The format of each line is command name Xfront Yfront Zfront Xrear Yrear Zrear Coordinates can be global centerline or reference if present Named Arguments coordinates Coordinate type global filename Filename to write file Synonym for filename coord Synonym for coordinates Alias for tessellatedsolid G4beamline User s Guide 88 tessellatedsolid construct a tessellatedsolid test timentuple 1 10 14 TJR A tessellatedsolid is defined by facets on its surface Each facet is either a triangle or a planar quadrilateral and of surfaces must be closed the set The surface definition can be read from a file or from the input file Leading whitespace is removed and represents a series of 0 or more non blank chars The first word in the line describes its content comment ignored tess also ignored v a vertex containing 3 doubles x y z in local coords ve a vertex containing an integer and 3 doubles index x y zZ 4 a facet containing 3 or 4 indexes into the v
46. has two rather serious deficiencies 1 it includes all tracks with no sigma cut so a single outlier track can have a large effect on sigmas and emittances 2 its emittance does not include the vector potential To avoid these deficiencies it may be better to write NTuples and apply an external program such as ecalc9 Named Arguments Z Comma separated list of Z positions for profiling mm zloop Loop in z first last incr mm require logical expression for cutting default true particle Name of particle to profile default mu file Output filename default stdout filename Synonym for file coordinates Coordinates centerline or reference default c control pseudo random number generator seeds This randomseed command controls the pseudo random number generator seed at the start of each event The unnamed argument can be any of case insensitive EventNumber None Time Set 12345 Now 12345 EventNumber is the default and permits events to be re run None does not re seed the PRNG at each event and Time is like None after seeding with the time of day in microseconds Set Now seeds the generator immediately with the value of the second argument a long and then acts like None 1 10 14 TJR Define a reference particle The reference particle is nominally headed in the Z direction Multiple reference particles can be defined at different positions momenta particle typ
47. height and width The wires are at angle theta from the vertical so theta 0 means vertical wires that measure x theta 90 means horizontal wires that measure y theta 180 also measures x but increasing x means decreasing wire Setting wireSpacing 0 means there are no wires which is useful for a trackerplane that models a scintillator used for track timing set sigmaTime gt 0 to indicate that sigmaTime gt 0 means this plane can measure the time of the track with that resolution A Gaussian random number is added to the true track s time at this plane when reading the TrackHit NTuple Survey errors can be modeled using the err arguments the values they specify are applied during trackfitting but not for true tracks errType fixed means error values given are th actual values gaussian means error values are the sigma of a Gaussian random number rect means error values are the half width of a uniform random number The random number is picked before the run begins the random number seed is set from the clock so every run will have different random errors trackerplane has 3 modes true The trackerplane reports the hit wire and time to the tracker fit The trackerplane reports the Chisq contribution of the fit track distance to the true track s hit wire center plus survey errors if any The track time also contributes to the chisq ignore Any track is ignored G4beamline User
48. in each segment of the centerline If no radiusCut is specified the ambiguities can become so bad that they prevent the use of centerline coordinates especially if there are many corners large angles or if the tune command is used which jumps the tune particle simulating a ring may not work at all without a radius Cut and needs the ring argument to the start command which assists in resolving the ambiguities unique to a ring 2 4 4 Reference Coordinates Reference coordinates are the usual coordinates used by accelerator physicists with the Z axis along the reference orbit X to the beam left and Y up In G4beamline the actual track of the reference particle is used for the Z axis As the reference track is stepwise linear between the physics steps of the tracking it is usually necessary to specify a rather small maxStep often 10 mm is about right Note these coordinates can be used only for output objects cannot be placed using them and tracking always uses global coordinates As an example consider a system having a uniform By 8 T with vacuum everywhere and a Gaussian beam injected with Py 0 centered on the Z axis there is a particlefilter to limit the number of turns each particle can take Each particle including the reference particle traces 6 circles that lay right on top of each other When using global coordinates for the trace the circles are quite evident using reference coordinates the tracks are sinusoid
49. innerRadius 700 outerRadius 725 length 1900 material Al color S vacuumPipeColor group RF radius 0 material Vacuum length 1900 place Pbhox z 690 rename C1 place Pbhox z 230 rename C2 place RFPipe z 0 place Pbox z 230 rename C3 place Pbox z 690 rename C4 endgroup HEH Cooling channel vacuum components HEH tubs vacuumPipeA innerRadius 200 outerRadius 255 length 285 material Al color S vacuumPipeColor group vacuumA radius 0 material Vacuum place vacuumPipeA endgroup Ht Lay out the MICE cooling channel use z 0 for the center of Absorber2 TrackerlEnd2 US edge is at z 29486 0 Het AUGOS value Cooling Channel TRD 09 09 2005 place OFFSET z 33180 1 place TOF1 z 6611 place IronShield z 6461 place End2 z 5951 rotation Y180 current 0 place Center z 5201 rotation Y180 current 0 place Trackerl z 4705 5 place Endl z 4451 rotation Y180 place Match2 z 4052 rotation Y180 place Matchl z 3611 rotation Y180 place vacuumA z 3317 5 place Focus z 2955 rotation Y180 place Absorber rename Absl1 z 2750 place Focus z 2545 place Coupl z 1375 place RF rename RF1 z 1375 place Focus z 205 place Absorber rename Abs2 z 0 place Focus z 205 rotation Y180 1 10 14 TJR G4beamline User s Guide 112 lace RF rename RF2 z 1375 lace Coupl z 1375 rotation Y180 lace Focus z 2545 rotation Y180 lace Absorber rename Abs3 z 2750 lace Focus z 2955
50. irean a i a a abe eg a ae a a aa 39 WAISCE MAIS OUS sercnrn reem E E N N A E E INE A T put File Descrpti iss in n N A A A E aA E a T E ANR a a ad AM EXPrESSIONS eire E vetoes aig eee sa E E E A Ae aia ew ae ets 42n Element Naeser rissie ses ar aaa E AEEA EAAS AREA EEEO tap haedn Masel AA OERS ARORA A 3s Parameters einna Og a Nc a a Na a ac eal hal Gat ee a a AA Pillbox Geometry and Dimensions ssssessesessssessesseseessessesresstestesresstesesresstesseserssressessessressesnt 4 5 Absorber geometry and Dimensions ss ssesessssessessresressesstesresstesesresstesesesstessesrsstessessessressesnt 46 Cornerare geometry enro eon ao a aE E Aa E EN EE E E Aaaa AA cgenencguad Pe PLUS a rnn a a ay Saucon E a a ey a n a a E R E ER 4 5 G4beamline Commands by Type s ss sessseesseseesssessessrssressessteseesseestesesstessesesseessesersstessessessressesne 5 G4beamline Commands Alphabetical ssnssesessseessessesseessessrsseesseesresesseeseesessseessesersseesesersseessessess 1 10 14 TJR G4beamline User s Guide 6 EAN TIO ES 5 E Wades Sian cs aa caercc tot a A a O e A asec tad evan Sosa 101 6 1 Examplel Simple Tracking and Virtualdetectors cccccccccccsseesseceteceseceeceeeseecsseceseeeeneeeaees 102 6 2 ExampleN02 g4bl The Geant4 ExampleNo2 0 0 ccc ccccccesecessceeseeeseeceaeceseeseceeescecsaecneeseneenaees 102 6 3 PPE PAINS OAD ti soca aeae E o a e dtd ccs canal e E E 103 6 4 St dy2 Cooling g4bb n n
51. is added A 2 mm square is 1 1 1 1 1 1 1 1 scalel The XY scale at the upstream z end 1 0 scale2 The XY scale at the downstream z end 1 0 maxStep The maximum stepsize in the element mm material The material of the extrusion color The color of the extrusion invisible kill Set nonzero to kill every track that enters vertexes Synonym for vertices implements a field map E and or B from expressions A fieldexpr element can be either a box or a cylinder set length and radius for cylinder set length and width and height for a box Units are Tesla MegaVolts meter mm and ns Expressions for the field components can use x y z for a box or z r for a cylinder the tim xpression can use t If present the time expression multiples all components Expressions can use all C operators except and x n is x to the nth power n integer The following functions are available abs min max sqrt pow sin cos tan asin acos atan atan2 sinh cosh tanh exp log log10 floor ceil if if condition a b replaces the C condition a b A field map is used for tracking efficiency the number of points in the map is increased until the largest map error divided by the maximum field is smaller than tolerance or 1M points is exceeded Similarly for the time dependenc For time dependence if t timeOffset lt tmin the val
52. it cannot be issued inside a group If radius height width 0 then no volume is associated with the corner and a bending magnet should be placed nearby to bend the particles around the corner Normally the bending magnet is placed before the corner and is rotated by half the bend angle For a sector bend it s usually best to use the cornerarc command rather than this one NOTE all placements before this command must have z values before the corner and all placements after this command must have z values after the corner Note also that the angle is limited to 90 degrees Note that the radiusCut is important to reduce or eliminate ambiguities in the global to centerline coordinate transform It can also be used to shield the beamline to prevent particles from taking unusual paths around the outside of beamlin elements Named Arguments Z The centerline Z of the corner mm rotation The rotation of the corner s above radiusCut The radius cut for this following segment mm default previous G4beamline User s Guide 51 cornerarc radius The radius of the circular corner volume mm height The height of the rectangular corner volume mm width The width of the rectangular corner volume mm length The length of the corner volume mm maxStep The maximum stepsize in the element mm material The material of the corner volume color The color of the corner volume
53. lace vacuumA z 3317 5 lace Matchl z 3611 lace Match2 z 4052 ace Endl z 4451 lace Tracker2 z 4705 5 lace Center z 5201 current 0 ace End2 z 5951 current 0 OO O 10 OOO OO O 0 10 lace IronShield z 6461 ko Downstream PID counters OFFSET for cooling channel still applies DS edge of Tracker2End2 6011 APPROXIMATION the octagonal Cherenkov2 is approximated as a circle APPROXIMATION an additional window is used in place of the mirror virtualdetector TOF2 height 480 width 480 length 50 8 color 1 1 1 material scintillator material aerogel density 0 2 Si 0 292 0 0 666 H 0 042 tubs Cherenkov2Window outerRadius 400 length 1 0 material Al color 0 0 1 virtualdetector Cherenkov2 radius 425 length 100 material aerogel color 0 0 1 tubs Cherenkov2Light outerRadius 640 length 367 material Air color 1 1 1 material calorimeter density 3 7 Pb 0 85 scintillator 0 15 virtualdetector Calorimeter width 1200 height 1200 length 160 material calorimeter color 0 1 1 SH He HEHEHE SHE lace TOF2 z 6586 4 lace Cherenkov2Window z 6710 5 lace Cherenkov2 lace Cherenkov2Light This Cherenkov2Window is standing in for the mirror so there are 2 lace Cherenkov2Window lace Cherenkov2Window lace Calorimeter z 7308 SO TWO H O OU U O Het an NTuple for good particles n tuple GoodParticle category NTuples detectors TargetDet TOFO Cherenkovl TOF1 SciFi TOF2 Ch
54. maxX would be appropriate for a horizontal transverse deflecting cavity Independent of how OdegRF is found exactly two of the set of maxGradient phaseAcc and one fixed output quantity fixMomentum fixEnergyGain fixTransitTime fixXdeflection or fixYdeflection must be specified to deterimine the final rfdevice timing For example with maxGradient and phaseAcc set the energy gain would be determined while if maxGradient and fixEnergyGain were set the phaseAcc would be determined The pipe walls and collars are made of copper by default Pipe wall collar winl and win2 may be omitted by setting their thickness to 0 Common usage is to set the collar values such that by placing multiple rfdevices sequentially the collars form a beam pipe between them Note that section 4 4 of the User s Guide has a dimensioned G4beamline User s Guide 83 drawing of a pillbox Due to the presence of an usually invisible timing volume care must be taken when placing objects within an rfdevice See the User s Guide for details on how to use this complex element Named Arguments cannot be changed in place cmd Tunable maxGradient The peak gradient of the cavity MV m color The color of the cavity frequency The frequency of the cavity GHz innerLength The inside length of the cavity mm innerRadius The inside radius of th
55. n a Oe ee a a R a a a a eee ney 103 6 5 MultipleScattering g4bl ein a a E a a aai 105 6 6 Tungsten Target g4bli aitnser e Ean Eea eas Ea R EEn e aE a aed ENAREN 105 6 7 MICE StageV L AI rnan ie a ta Ea E E a EEE ol lt eal ky 106 6 8 Ideahzed De 4bl Ropes rs case cea ds cc se T E E T a A i E A a EE naetes 113 6 9 MSpace Nate OA DN oaks ae e ah a e a a a a a aa 114 6 10 Sample Movie GAD nmr enei i a aa ia TE EE Aisa E E aT Aisa 116 a MA BE N K Aa EYS 1 PE AE E A EE E O EEA 116 6 12 triplet sh tune a quad triplet for point to point focus ss sessessesessessessesseseesesseseessssersessesee 117 6 13 emittancematch sh attempt to match a quad triplet into a solenoid e cee eeeeeeeeeeteeeeeee 118 T Hpsa d TechiigueS eonan a a naaa a aa a EE A E E E AOR SR 119 7 1 Getting Help on Using G4beamline sssseseseeseeseesseesseseessessessesseessesstesresseeseesesseeseesrrssessesers 119 7 2 Reporting Bugs in G4beamline ise occas cc aeie cs ga Sdades sc oace Nas aus san mucaes yoSdeabuad sane Noten cae aeunie abd eeaa as 119 7 3 Requesting New Features in G4beamline is cases csasecepsassinausnsiscandsnrenasevatecaphacsdesaaerstapbaaninetbaeeds 119 74 Getting Help on Individual G4beamline Commands 0 0 0 0 cece cccecsseceseceeeeeeeeeeseeceaecnseeeeeeenaees 119 7 5 In what Directory should I Work cena eccacsavaceodeysceceondsedaeians do caoncdacadenedtbsoeNopatstaace uaatnaenedens 120 7 6 Files Common to Multiple Simulations 2
56. of deflecting cavities or very slow particles will the methods give much differing results The default method is timingMethod atZlocal where the timing is adjusted so the particle would arrive at the local to the rfdevice timingZlocal location default is 0 mm inside the rfdevice at the appropriate phase this was used in earlier versions of G4beamline In actual practice however most people adjust a real cavity for maximum energy gain timingMethod maxEnergyGain corresponding to 90 RF for a positive particle and 270 RF for a negative particle When using a multicell cavity the latter method is usually preferable 1 10 14 TJR G4beamline User s Guide 160 For special cases including deflecting cavities other methods of determining the base timing are available as shown in the following table Here the transit time is considered relative to the drift time so timingMethod noTransitTime corresponds to the same transversal time as a simple drift Available timingMethods for determining 0 RF method abbreviation default description timingAtZ atZlocal atZ middle used by G4beamline 2 08 and earlier generally not used with fix output requirements maxEnergyGain maxE exit most common method for most RF noEnergyGain noE exit for RF bunchers minEnergyGain minE exit for decelerating RF maxTransitTime maxT exit for special applications noTransitTime noT exit for special applications min
57. parameter and any parameter can be set on the G4beamline command line gminuit can be used to tune any value in your input file based on any 1 10 14 TJR G4beamline User s Guide 145 criterion you can script It is possible to determine the gminuit value to minimize by either reading the output from G4beamline with steppingVerbose 1 tailor steppingFormat to suit or by reading the file generated by virtualdetector format ascii or trace format ascii Remember that most shells only do integer arithmetic so it is appropriate to use a tcl or perl script to interpret the G4beamline output and return a value for gminuit to minimize See the gminuit documentation for details The file examples triplet sh is an example that uses gminuit to tune a quad triplet 8 2 Violating the Rules on Geometrical Intersections Geant4 tracks particles through the geometry hierarchy by looking for the next geometrical boundary along the track s path and arranging so there is a step that ends at each boundary crossed by the track To keep the search for boundaries efficient Geant4 only looks for the outer boundary of the current volume and for boundaries of all daughter volumes of the current volume So if sibling volumes A and B overlap if the track enters A first then it will be tracked in A through the region of intersection but if it enters B first then it will be tracked in B through the region of intersection Similarly if a daughter A1 of A extends outsid
58. parameters are constant mean sigma Note that after typing a user expression you MUST do Set parameters or you will get an error Function with name does not exist There is a button to set the initial values and ranges of the parameters for the selected function There are a number of options If you select Use range then the double slider below becomes active and will set the range of the fit displayed visually in the plot as you move the slider ends When fitting it is useful to check the plot s menu item Options FitParameters so the fit results are displayed in the statistics panel of the plot you can drag its edges to make it larger and its font will scale For further details see the Root documentation 1 10 14 TJR G4beamline User s Guide 136 Note that if you want to play with backgrounds you can select Options CanEditHistograms then with the mouse you can drag any histogram bin s value up or down as you wish You can then re fit to see how your changes affect the results 7 28 Interfacing to Other Programs Many different file formats are used in physics today and no program can implement all of them G4beamline supports ASCII file formats that are suitable for interfacing to other programs including both track files and field maps A conversion program in C or Java can easily be written to read an ASCII file and write another in a different format e g new order of items different units etc Roo
59. process spinTracking 1 will enable tracking the spins of e e mut and mu only including pion decays to polarized muons polarized muon decays and the force from the particle s magnetic moment The rare pion decay to e nu is included but the e are unpolarized The muon decays give the correct distribution for the electron but only approximate distributions for the neutrinos and all are unpolarized NOTE this command defines the particles used throughout the simulation so this command must come before others that use particle names T NOTE the rare decay mode for pi pi to e nu is always added with branching ratio 1 230E 4 The default all around physics list for HEP is called FTFP BERT NOTE At present there is a bug in Geant4 tracking and the magnetic moment is not used For gt 1 GeV muons and practical G4beamline User s Guide 74 http geant4 web cern ch geant4 support physicsLists referencePL index shtml 1 10 14 TJR fields this is a very small error Named Arguments disable Comma separated list of processes to disable e g Decay msc inactivate Synonym of disable deactivate Synonym of disable doStochastics Set to zero to disable all stochastic processes fluct Set to zero to disable ionization energy loss fluctuations min lis RangeCut Minimum range cut for particle production 1 mm a Nonzero to list the processes later in output
60. reference in y mm dz Max distance of particle to reference in z mm nxApprox bins in x in approximation 7 nyApprox bins in y in approximation 7 G4beamline User s Guide 86 nzApprox bins in z in approximation 7 maxBeta Max beta v c of particle in beam frame 0 1 verbose Non zero for verbose prints 0 ignoreFieldWhenTracking For testing only 0 useApproximationOnly For testing only 0 fixedGrid Nonzero prevents re sizing the grid 0 percentil Percentile of charge distribution used for grid Sizing 99 minActive Minimum active tracks in bunch if lt 0 is of initial bunch size 95 spacechargelw Lienard Wiechert space charge computation sphere 1 10 14 TJR This is a space charge computation that uses macro particles to Simulate more particles than is feasible Each macro particle is tracked as a singl charge is multiplied by the macro particl Singularity from a point charge outside the point charge field is multiplied by K are parameters The trajectory of every particle is kept field at a point the intersection of the with the trajectory is used to determin to track individually e particle but its e charge when computing the field The radius of the macro particle is used to avoid the the radius the macro particle is treated as a point charge inside the radius r radius K radius and and when computing the point s past ligh
61. replaced by trackId for oneNTuple the default filename is AllTracks txt Note that without a trace command no traces are generated so to trace just the tune and reference particles include a trace command with no arguments In collective tracking mode oneNTuple must be nonzero and the entries will be generated only at collective steps usually ata specified deltaT Unlike other NTuple commands the requir xpression applies to entire tracks not individual entries The standard NTuple fields are X Y Z mm Px Py Pz MeV c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 The trace includes the following fields Bx By Bz Tesla Ex Ey Ez Megavolts meter The following additional fields are appended for format Extended format asciiExtended and format rootExtended ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Valid Formats ignore case ascii bltrackfile dummy for009 for009 dat root trackfile Extended asciiExtended rootExtended Named Arguments cannot be changed in place cmd nTrace Number of tracks to trace format Format of the NTuple see above for list 1 10 14 TJR G4
62. rho 1700 rho 1700 rho 1700 0 rhot rho rho0 rho3 1690 1 10 14 TJR PDGid 321 PDGid 321 PDGid 311 PDGid 130 PDGid 310 PDGid 3122 PDGid 13122 PDGid 3124 PDGid 23122 PDGid 33122 PDGid 13124 PDGid 43122 PDGid 53122 PDGid 3126 PDGid 13126 PDGid 23124 PDGid 3128 PDGid 23126 PDGid 4122 PDGid 13 PDGid 13 PDGid 2112 PDGid 12 PDGid 14 PDGid 16 PDGid 223 PDGid 100223 PDGid 30223 PDGid 3334 PDGid 227 PDGid 4332 PDGid 0 PDGid 333 PDGid 100333 PDGid 337 PDGid 100211 PDGid 100211 PDGid 100111 PDGid 211 PDGid 211 PDGid 111 PDGid 10215 PDGid 10215 PDGid 10115 PDGid 2212 PDGid 100213 PDGid 100213 PDGid 100113 PDGid 30213 PDGid 30213 PDGid 30113 PDGid 213 PDGid 213 PDGid 113 PDGid 217 G4beamline User s Guide 196 rho3 1690 rho3 1690 0 s_ quark sd0Q_ diquark sdl_ diquark sigma 1385 sigma 1385 sigma 1385 0 sigma 1660 sigma 1660 sigma 1660 0 sigma 1670 sigma 1670 sigma 1670 0 sigma 1750 sigma 1750 sigma 1750 0 sigma 1775 sigma 1775 sigma 1775 0 sigma 1915 sigma 1915 sigma 1915 0 sigma 1940 sigma 1940 sigma 1940 0 sigma 2030 sigma 2030 sigma 2030 0 sigmat sigma sigma0 sigma_c sigma_c sigma_c0 ssl _ diquark su0_ diquark sul_diquark t_quark taut tau triton u_quark ud0_diquark udl_diquark uul_diquark xi 1530 xi 1530 0 xi 1690 xi 1690 0 xi 1820 xi 1820 0 xi 1950 xi 1950 0 xi 2030 1 10 14 TJR PDGid 2
63. sequentially from 1 the primary TrackID s are assigned sequentially from 1 within each event and secondary TrackID s are assigned sequentially from the secondaryTrackID argument to the beam command default 1001 This means that when generating a beam file to be read into G4beamline you can assign both EventID s and TrackID s in whatever manner you like subject to the above constraints For instance you could assign bins to the phase space of a generated beam and set either EventID or TrackID to the bin number of each track in the beam file After running G4beamline to determine which tracks are accepted by the system a plot of the acceptance can be made by post processing the output file with knowledge of how many tracks were generated in each bin 7 30 Examining Outlier Events It often happens that some sort of puzzling event occurs or an outlier entry appears in some histogram Here is a method to find such events and then visualize them As a simple example consider this bending magnet red followed by a virtualdetector green with 100 beam tracks shown blue 1 10 14 TJR G4beamline User s Guide 137 45 40 35 30 25 20 15 10 5 0 Eile Plot Help NTuple This looks fine until one runs 1 000 events and histograms x in the virtualdetector clearly there is an outlier track at x 1500 KERT p ERAN A EEE ERE LPL USUI LPL RERA x at the green virtualdetector Plott Entries 991 Mean 399
64. several tens of meters This command does nothing if not in visualization mode For best results use the Open Inventor viewer and give your magnets a transparency of about 0 3 e g color 1 1 1 0 3 if necessary use the right button menu to set the DrawStyle TransparencyType to sorted object add With field lines in 3 d you will want the ability to zoom rotate and move the image interactively Setting exit 1 will display the system and the field lines without any event tracks exiting the viewer will then exit the program With exit 0 field lines are drawn only at the end of the first run Named Arguments Time at which field lines are plotted 0 ns center Center of circle x y z to start lines mm global G4beamline User s Guide 58 fieldmap fieldntuple 1 10 14 TJR radius Radius of circle to start lines mm nLines Approximate number of field lines to plot 100 dl Interval between points plotted 10 mm color Color of field lines white 1 1 1 minField Minimum B field 0 001 tesla maxPoints Max points plotted in a line 10000 subdivide field integration points between plotted points 10 N grid points in x and y 128 exit Set nonzero to display field lines and exit 0 square Set nonzero to start from square rather than circle 0 Efield Set nonzero to draw E field 0 minField is in MegaVolts meter forever Set nonzero to draw
65. the desired acceleration of the reference particle is achieved 3 Automatically set the field of bending magnets so the Reference particle is parallel to the centerline downstream of the magnet 4 Automatically determine the initial momentum of the Reference particle so that it has a specified momentum at some later point in the beamline Unfortunately this method cannot be used to tune the position of bending magnets because of their fringe fields the center of a bending magnet must normally be offset by a small distance downstream of the corner in order to make the Reference particle go right down the centerline after the magnet As an example consider tuning the By value of a genericbend reference referenceMomentum 200 particle mut beamZ 0 0 tune B1 z0 100 z1 3000 initial 0 6500 step 0 01 expr Px1 Pz1 tolerance 0 000001 genericbend B fieldWidth 500 fieldHeight 500 fieldLength 500 ironWidth 800 ironHeight 800 ironLength 500 fieldMaterial Vacuum place B z 2000 rename Bl rotation Y15 By B1 corner C z 2000 rotation Y30 The tune command specifies to tune the value B1 so that at Z 3000 the expression Px Pz will be zero to within the tolerance of 0 000001 That is that the Reference particle be parallel to the centerline within a microradian The genericbend named B1 uses the tune variable B1 as its By argument value What happens is that when the Tune particle reaches z0 100 it is saved and
66. the visualization Just ignore them 7 31 Increasing the Number of Events Displayed Visually By default the maximum number of events displayed in a viewer is 100 To increase this limit to 1000 events execute this command g4ui when 4 vis scene endOfEventAction accumulate 1000 7 32 Building G4beamline Adding Your Own Code There are several reasons why you might want to build G4beamline from source e You want to run it on an unsupported system or OS e You want to optimize it for your system e g a 64 bit build e You want to add your own new feature or code 1 10 14 TJR G4beamline User s Guide 139 Before you can add your own code to G4beamline you must build it from source Read BUILD txt and README txt in the doc directory of any distribution for details Note the required tools and the details of the build procedure differ for different OSs Once you have built G4beamline from source test that g4b make works on your system cd test test72 If this says test 72 compiling user code omitted then there is an error in your configuration If test72 takes 20 30 seconds and prints nothing but its 1 line synopsis then it succeeded all tests succeed silently but print an error on failure Now you are ready to add your own code First create a directory in which to work for this example P11 call it testing cd mkdir testing cd testing copy or create your new code in a file such as testing cc g4blmak
67. to carefully adjust their maxGradient so the output beam has the desired energy or momentum The operators of the machine arrange for this either manually or via an automated feedback system In G4beamline this can be done two ways The first is the autoTiming technique and it is local to just its own rfdevice requiring no information from downstream locations In this method generally both the appropriate timingMethod maxE and the step size maxStep ought to be specified as the defaults may not be good choices rfdevice timingMethod maxE maxStep 1 timeOffset tabsolute NS fixMomentum Pour MeV c phaseAcc degRF fixEnergyGain AE MeV phaseAcc 9 degRF fixMomentum Pour MeV c Common gradient finding option combinations The second technique requires the tune command and is done while tracking the Tune Event 2 particle usually in parallel with setting their phases see previous section The tune command defines a tune variable and will arrange to save the Tune particle at one Z position z0 track the Tune particle to a second Z position z1 and then evaluate an expression using track fields It then varies its tune variable in an attempt to make the expression evaluate to 0 0 This of course requires that some relevant beamline elements between z0 and z1 use the tune variable to change their behavior appropriately In this case we ll vary the maxGradient of all RF cavities between z0 and z1 and use an expressi
68. to run it you need to have all the necessary libraries and physics data sets available in your environment which happens when a you setup to build G4beamline b you run the g4b script c you run the g4b gui script or d you double click the G4beamline icon In addition the g4b command arguments can contain commands to be interpreted before reading the input file These are interpreted in the order given after all the parameters on the command line are defined If the command has arguments it must be quoted because of the spaces between arguments The usual commands this is used for are eventcuts used by g4b gui and movie used by users to add the movie NTuples to an existing simulation g4bl input file movie namel valuel name2 value2 For visualization the viewer def file is looked for in the current directory and then in the directory from G4BL_DIR in your environment If you aren t using the g4b script you probably want to set G4BL_DIR to the distribution directory so you don t need to link viewer def into every working directory G4BL_DIR is set when you setup to build G4beamline and also by g4bl g4blgui and the icon G4beamline has two modes of operation visualization and tracking If the parameter viewer has been set to anything other than none it will run in visualization mode which displays an image of the simulated system as specified in the viewer def file for the viewer specified For viewer none the default
69. tracked to z1 3000 which goes through the genericbend B1 When the Tune particle reaches z1 3000 the expr Px1 Pz1 is evaluated and if it is within tolerance of zero the tuning is complete If it is out of tolerance a simple linear solver is used to update the value of the variable B and the saved track from z0 100 is re tracked to z1 3000 and the process is repeated If the process does not converge with 10 attempts the tuning fails and the program exits information about each step is written to stdout The other tune procedures are similar in that the Tune particle track is saved upstream of the region to be tuned and downstream of the region its properties are used to modify a variable that affects the tuning and the saved track is re tracked until the result is within tolerance In practice it is often necessary to use multiple tune commands They must be properly nested so each tuning region is either disjoint from the others or is wholly contained in one or more other regions separation of 0 01 mm is usually adequate For instance in a muon cooling channel with bending magnets and RF cavities it is probably necessary to tune the reference momentum the bending magnets and the RF gradient s Note that g4beamline can only tune based on the Tune particle and can only tune tunable arguments to certain commands These limitations are due to technical details of the implementation and cannot 1 10 14 TJR G4beamline User s
70. wall clock time Note that it can take several seconds to several minutes to close up so the value of the G4beamline parameter should be suitably 1 10 14 TJR G4beamline User s Guide 29 smaller than the limit of the job This limit is checked only between events which is another reason it should be smaller than the job limit 2 15 Event and Track Numbering EventID TrackID EventID is intended to identify a particular event which may have multiple tracks In G4beamline each beam track is a separate event For internally generated beams EventID is incremented for each beam track and is thus unique within a given run For beams read from external files the assignment of EventID s to tracks is contained in the file this means that multiple events can have the same EventID and that EventID s might not be monotonically increasing Moreover NTuple s use float s to hold each data item and a float has only 24 bits of mantissa This implies that any event number gt 16 777 216 will be truncated This applies to both reading and writing Root files Two workarounds avoid this truncation for many cases e BLTrackFile format ASCII avoids the truncation internally both reading and writing e Commands that generate a track NTuple will map format ascii to format bltrackfile This includes beamlossntuple newparticlentuple timentuple virtualdetector zntuple The result is that this truncation of EventID occurs only for Root NTuples and i
71. 0 0 ccccceecceeseeesseesseceseceeeeeeeeeseecsaeeneeeeeeenaees 139 7 33 Displaying Magnetic Field Lines is3 243csdcctbatdazacchandiasssaduet vaek aaehlslastedeonlastecdeeiaeeishcasiatmanvaeies 141 7 34 Setting the Phase of RE Cavities rfdevice is a tisssccissdecnestecaedsventeses jase et addenda hte Quads 142 7 35 Tuning the maxGradient of RF Cavities rfdevice cecceceeseeseceneceeeeeeeeeeseecsaeceeeeeeeenaees 143 8 Ady nced TOpiCS aeneae nen c bested an auc Garant ash poet RER e Sansui as 145 8 1 Writing Scripts Using G4beamline ic csscicictedecs hes cavecsssdcnscavsvkavncsadsee Ata cesvtededcns ataveestndascd Aaa cuess 145 8 2 Violating the Rules on Geometrical Intersections cccecceeceesceececeseceeeeeeeeeseecaecneeneeeennees 146 8 3 Making a Mow ie cxesccts ety bei scaescsiayastenancs EE AE E aba eres nee aaa eds 146 8 4 User Code for the usertrackfilter Command 000 ccc ceecceccccceseceneceeecesscecsaeceseceeeeenseecaecneeneneenaees 151 8 5 Multiple Instances of G4beamline using MPI czcccssasdeccsscdescesdncsiteasediessaatden ddaustesdedssttaatdev ees 152 8 6 G4beamline Helper Programs and Scripts cccecceesessseeseceseceeeeeeseecaeceseceeeeeeseecsaecnteeseeeensaes 157 Bed Setting Up AIT VICE he sco conan e se ade den E A a E E E R ERER 159 9 Fil Formatieren a oR a Ee eS ee eee re 171 9 1 BLTrackFile generated by NTuple s read by beam 0 ccceccceccceesseesseceteceseceeeeesscecuecnseeneneensaes 171 92 Tra
72. 0 0 k2_star 1980 k2_star 1980 k2_star 1980 0 k3_star 1780 k3_star 1780 k3_star 1780 0 k_star 1410 k_star 1410 k_star 1410 0 k_star 1680 k_star 1680 k_star 1680 0 k_start k_star k_star0 1 10 14 TJR PDGid 100221 PDGid 9020221 PDGid 100331 PDGid 10225 PDGid 10335 PDGid 331 PDGid 10221 PDGid 9030221 PDGid 10331 PDGid 9000221 PDGid 9010221 PDGid 20223 PDGid 20333 PDGid 225 PDGid 9030225 PDGid 9060225 PDGid 335 PDGid 22 PDGid 0 PDGid 21 PDGid 10223 PDGid 10333 PDGid 100321 PDGid 100321 PDGid 100311 PDGid 10321 PDGid 10321 PDGid 10311 PDGid 10323 PDGid 10323 PDGid 10313 PDGid 20323 PDGid 20323 PDGid 20313 PDGid 10325 PDGid 10325 PDGid 10315 PDGid 325 PDGid 325 PDGid 315 PDGid 100325 PDGid 100325 PDGid 100315 PDGid 327 PDGid 327 PDGid 317 PDGid 100323 PDGid 100323 PDGid 100313 PDGid 30323 PDGid 30323 PDGid 30313 PDGid 323 PDGid 323 PDGid 313 G4beamline User s Guide 195 kaon kaon kaon0 kaon0L kaon0s lambda lambda 1405 lambda 1520 lambda 1600 lambda 1670 lambda 1690 lambda 1800 lambda 1810 lambda 1820 lambda 1830 lambda 1890 lambda 2100 lambda 2110 lambda_ct mu mu neutron nu e nu mu nu_tau omega omega 1420 omega 1650 omega omega3 1670 omega_c0 opticalphoton phi phi 1680 phi3 1850 pi 1300 pi 1300 pi 1300 0 pit pi pid pi2 1670 pi2 1670 pi2 1670 0 proton rho 1450 rho 1450 rho 1450 0
73. 1 20 March 2012 Copyright Geant4 Collaboration Reference NIM A 506 2003 250 303 WWW http cern ch geant4 KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK geometry nPoints 100 printGeometry 0 visual 0 tolerance 0 002 Here are some lines beginning with from the input file Examplel g4bl simple first example Simpl xample g4beamline input file a 200 MeV mu Gaussian beam is tracked through l1 meter drift spaces into four detectors ah BRS OE Es ah Some output from the physics command comes before the command itself G4PhysListFactory GetReferencePhysList lt QGSP BERT gt EMoption 0 lt lt lt Geant4 Physics List simulation engine QGSP_ BERT 3 4 lt lt lt Reference Physics List QGSP_ BERT is built physics QGSP_BERT disable inactivate deactivate doStochastics 1 minRangeCut 1 list 0 gammaToMuPair 0 spinTracking 0 synchrotronRadiation 0 synchrotronRadiationMuon 0 Next is the beam command beam GAUSSIAN particle mu nEvents 1000 firstEvent 1 lastEvent 2147483647 beamX 0 0 beamY 0 0 beamZ 0 0 maxR 1000000 0 meanMomentum 200 0 weight 1 000000 1 10 14 TJR G4beamline User s Guide 186 sigmaX 10 0 sigmaY 10 0 sigmaZ 0 0 sigmaXp 0 10000 sigmaYp 0 10000 SigmaP 4 0 sigmaT 0 000 meanXp 0 00000 meanYp 0 00000 meanT 0 000 The rest of the commands from the input file referen
74. 124 PDGid 1214 PDGid 22212 PDGid 22112 PDGid 32212 PDGid 32112 PDGid 2216 PDGid 2116 PDGid 12216 PDGid 12116 PDGid 22124 PDGid 21214 PDGid 42212 PDGid 42112 PDGid 32124 PDGid 31214 PDGid 42124 PDGid 41214 PDGid 12218 PDGid 12118 PDGid 52214 PDGid 52114 PDGid 2128 PDGid 1218 PDGid 100002210 PDGid 100002110 PDGid 100012210 PDGid 100012110 PDGid 10211 PDGid 10211 PDGid 10111 PDGid 9000211 PDGid 9000211 PDGid 9000111 PDGid 20213 PDGid 20213 PDGid 20113 PDGid 215 G4beamline User s Guide 190 a2 1320 a2 1320 0 alpha anti_BO anti_Bs0 anti_DO anti_N 1440 anti_N 1440 0 anti_N 1520 anti_N 1520 0 anti_N 1535 anti_N 1535 0 anti_N 1650 anti_N 1650 0 anti_N 1675 anti_N 1675 0 anti_N 1680 anti_N 1680 0 anti_N 1700 anti_N 1700 0 anti_N 1710 anti_N 1710 0 anti_N 1720 anti_N 1720 0 anti_N 1900 anti_N 1900 0 anti_N 1990 anti_N 1990 0 anti_N 2090 anti_N 2090 0 anti_N 2190 anti_N 2190 0 anti_N 2220 anti_N 2220 0 anti_N 2250 anti_N 2250 0 anti_b quark anti_c_quark anti_d_quark PDGid 215 PDGid 115 PDGid 1000020040 PDGid 511 PDGid 531 PDGid 421 PDGid 12212 PDGid 12112 PDGid 2124 PDGid 1214 PDGid 22212 PDGid 22112 PDGid 32212 PDGid 32112 PDGid 2216 PDGid 2116 PDGid 12216 PDGid 12116 PDGid 22124 PDGid 21214 PDGid 42212 PDGid 42112 PDGid 32124 PDGid 31214 PDGid 42124 PDGid 41214 PDGid 12218 PDGid 12118 PDGid 52214 PDGid 5211
75. 17 PDGid 117 PDGid 3 PDGid 3101 PDGid 3103 PDGid 3224 PDGid 3114 PDGid 3214 PDGid 13222 PDGid 13112 PDGid 13212 PDGid 13224 PDGid 13114 PDGid 13214 PDGid 23222 PDGid 23112 PDGid 23212 PDGid 3226 PDGid 3116 PDGid 3216 PDGid 13226 PDGid 13116 PDGid 13216 PDGid 23224 PDGid 23114 PDGid 23214 PDGid 3228 PDGid 3118 PDGid 3218 PDGid 3222 PDGid 3112 PDGid 3212 PDGid 4212 PDGid 4222 PDGid 4112 PDGid 3303 PDGid 3201 PDGid 3203 PDGid 6 PDGid 15 PDGid 15 PDGid 1000010030 PDGid 2 PDGid 2101 PDGid 2103 PDGid 2203 PDGid 3314 PDGid 3324 PDGid 23314 PDGid 23324 PDGid 13314 PDGid 13324 PDGid 33314 PDGid 33324 PDGid 13316 G4beamline User s Guide 197 xi 2030 0 PDGid 13326 xi PDGid 3312 xi0 PDGid 3322 xi c PDGid 4232 xi c0 PDGid 4132 1 10 14 TJR G4beamline User s Guide 198 Appendix 7 Error Messages Errors and warnings generated during execution are handled by the G4Exception function they are printed as a 7 line message starting and ending with a row of asterisks that makes them stand out visually in a long printout Those that are issued by a routine beginning with G4 came from Geant4 code while those issued by a routine beginning with BL came from G4beamline code those that are issued by a command name are also from G4beamline code This list may not be complete it does not attempt to list all error messages from libraries such as Geant4 CLHEP GSL OpenInventor OpenGL
76. 4 PDGid 2128 PDGid 1218 PDGid 100002210 PDGid 100002110 PDGid 100012210 PDGid 100012110 PDGid 5 PDGid 4 PDGid 1 anti_ddl_ diquark PDGid 1103 anti_delta 1600 PDGid 32214 anti_delta 1600 PDGid 32224 anti_delta 1600 PDGid 31114 anti_delta 1600 0 PDGid 32114 anti_delta 1620 PDGid 2122 anti_delta 1620 PDGid 2222 anti_delta 1620 PDGid 1112 anti_delta 1620 0 PDGid 1212 anti_delta 1700 PDGid 12214 anti_delta 1700 PDGid 12224 anti_delta 1700 PDGid 11114 anti_delta 1700 0 PDGid 12114 anti_delta 1900 PDGid 12122 anti_delta 1900 PDGid 12222 anti_delta 1900 PDGid 11112 1 10 14 TJR G4beamline User s Guide anti_delta 1900 0 PDGid 11212 anti_delta 1905 PDGid 2126 anti_delta 1905 PDGid 2226 anti_delta 1905 PDGid 1116 anti_delta 1905 0 PDGid 1216 anti_delta 1910 PDGid 22122 anti_delta 1910 PDGid 22222 anti_delta 1910 PDGid 21112 anti _delta 1910 0 PDGid 21212 anti_delta 1920 PDGid 22214 anti_delta 1920 PDGid 22224 anti_delta 1920 PDGid 21114 anti_delta 1920 0 PDGid 22114 anti_delta 1930 PDGid 12126 anti_delta 1930 PDGid 12226 anti_delta 1930 PDGid 11116 anti_delta 1930 0 PDGid 11216 anti_delta 1950 PDGid 2218 anti_delta 1950 PDGid 2228 anti_delta 1950 PDGid 1118 anti_delta 1950 0 PDGid 2118 anti_delta PDGid 2214 anti_delta PDGid 2224 anti _delta PDGid 1114 anti_delta0 PDGid 2114 anti_k 1460 0 PDGid 100311 ant
77. 4 TJR G4beamline User s Guide 35 4 Input File Description A G4beamline simulation is completely specified in a single ASCII input file plus whatever auxiliary files it references e g magnetic field maps window profiles etc Each line in the input file is either a comment or a command Comments are blank lines lines beginning with and lines beginning with which are printed to stdout giving a convenient method to document your output files Lines beginning with are commands passed directly to the Geant4 user interface command interpreter this happens before the geometry is initialized see the g4ui command to defer execution of Geant4 UI commands Lines beginning with are passed directly to the shell with the stripped On any line introduces a comment to end of line if it is preceded by a space or tab and is not enclosed in quotes A command is a single line beginning with the command name optionally preceded by white space followed by any number of arguments Lines can be continued by preceding the ending newline with a backslash Commands can have any combination of positional and named arguments which are separated by white space spaces or tabs A named argument is of the form name value where the name is like a C identifier except it can also contain the characters and which are needed for particle names If spaces or tabs are present in the value t
78. 5 delta 1905 0 delta 1910 delta 1910 delta 1910 delta 1910 0 delta 1920 delta 1920 delta 1920 delta 1920 0 delta 1930 delta 1930 delta 1930 delta 1930 0 delta 1950 delta 1950 delta 1950 delta 1950 0 deltat deltat delta delta0d deuteron e e eta 1 10 14 TJR PDGid 3322 PDGid 4232 PDGid 4132 PDGid 10213 PDGid 10213 PDGid 10113 PDGid 5 PDGid 4 PDGid 0 PDGid 1 PDGid 1103 PDGid 32214 PDGid 32224 PDGid 31114 PDGid 32114 PDGid 2122 PDGid 2222 PDGid 1112 PDGid 1212 PDGid 12214 PDGid 12224 PDGid 11114 PDGid 12114 PDGid 12122 PDGid 12222 PDGid 11112 PDGid 11212 PDGid 2126 PDGid 2226 PDGid 1116 PDGid 1216 PDGid 22122 PDGid 22222 PDGid 21112 PDGid 21212 PDGid 22214 PDGid 22224 PDGid 21114 PDGid 22114 PDGid 12126 PDGid 12226 PDGid 11116 PDGid 11216 PDGid 2218 PDGid 2228 PDGid 1118 PDGid 2118 PDGid 2214 PDGid 2224 PDGid 1114 PDGid 2114 PDGid 1000010020 PDGid 11 PDGid 11 PDGid 221 G4beamline User s Guide eta 1295 eta 1405 eta 1475 eta2 1645 eta2 1870 eta_prime 0 1370 0 1500 0 1710 0 600 0 980 1 1285 1 1420 2 1270 2 1810 2 2010 2 prime 1525 gamma geantino gluon h1 1170 h1 1380 k 1460 k 1460 k 1460 0 kO_star 1430 kO_star 1430 kO_star 1430 0 k1 1270 k1 1270 k1 1270 0 k1 1400 k1 1400 k1 1400 0 k2 1770 k2 1770 k2 1770 0 k2_star 1430 k2_star 1430 k2_star 143
79. AG CL STEP VOL MAT PROCESS B Beamline tune parameters AUGO5 piMomentumRef is the pion reference momentum at target muMomentum is the muon design momentum at center of B2 muMomentumRef is the muon reference momentum at center of DecaySolenoid account for Eloss in vacuum window air and ProtonAbsorber slight change in B2 field and position compared to Kevin s AUGO5 due to Eloss in air param unset piMomentumRef 440 42 muMomentum 255 24 muMomentumRef 266 0 param unset DecaySolenoidCurrent 86 02 param unset Q1 1 155989 Q2 1 445 Q3 1 005937 param unset B1l 1 41384 B1z 7918 02 param unset B2 0 424270 B2z 15791 47 Kevin s values param B1l 1 413935 B2 0 424573 param unset Q4 1 13004 Q5 1 477795 Q6 0 80022 param unset Q7 0 98765 Q8 1 520426 Q9 1 43098 param unset DiffuserThickness 7 6 Hitt Colors tt param unset vacuumPipeColor 0 6 0 6 0 6 Hitt general definitions HHH param worldMaterial Air maxStep 100 0 physics QGSP BIC trackcuts keep proton pit mut et t e kineticEnergyCut 30 maxTime 1000 particlecolor proton 1 0 0 pit 0 1 0 mu 0 0 1 plus 1 0 1 minus 1 1 0 neutral 0 1 1 reference 1 1 1 coil default material Cu dR 5 0 dZ 5 0 tolerance 0 001 solenoid default color 1 1 0 Target is lmm wide and 10mm long 1 cos 25 deg 10 sin 25 deg 2 2 57 For now we assume the target dips 2mm into the ISIS beam sigmaP sigmaXp
80. AUG2105 p3v3 xls The vacuum windows and pipes are my best GUESS this needs to be properly designed APPROXIMATION the vacuum windows are flat The MICE magnetic lattice for the cooling channel is Stage VI flip beta 42 cm from UB 09 04 A TJR I added the column Center Z The downstream PID detector layout is from cm9 palladino pidupdate pdf Except I have used a total of 1 scintillator for TOF2 APPROXIMATION The DecaySolenoid map is for 3 7 T scaled to 4 172 T APPROXIMATION The RF layout is from Study2 not updated APPROXIMATION I have an old spreadsheet for computing the absorber and safety window profiles APPROXIMATION the outer shapes of quads and bends are wrong but there are no particles of interest out there so that s OK APPROXIMATION neglect the varying density of the ISIS beam over the target APPROXIMATION the ISIS vacuum and pipe do not implement ISIS at all 1 10 14 TJR G4beamline User s Guide 106 but are OK for our pions APPROXIMATION the vacuum between Q3 and Bl is a box without any pipe APPROXIMATION the vacuum between B1 and DecaySolenoid is a box without any pipe command line parameter default values param unset first 0 last 10000 viewer none Absorber material LH2 or Vacuum param unset absMaterial Vacuum HistoScope filename from first event param histoFile Sfirst histoUpdate 100000 param steppingFormat T
81. FFTW Xwindows etc Exception Severity Discussion 001 Warning G4HadronicProcess this is a coding error and is being investigated by the Geant4 team It is rare and can be ignored unless a large number of tracks are affected Alarm Signal Fatal The alarm timer fired This timer is set 10 seconds longer than the eventTimeLimit and will only fire if no steps were taken during those extra 10 seconds Usually indicates an infinite loop somewhere in the program Missing material Fatal The specified material cannot be found UnknownParticle Fatal The specified particle does not exist Cannot Tune Fatal The pillbox cannot be tuned properly Tune Iteration Limit Fatal The pillbox tuning did not converge Invalid Step Fatal The pillbox tuning made an invalid step Tuning failed to converge Fatal Tuning did not converge Overwriting input file Fatal The trackermode filename is the same as the parameter histoFile which will overwrite the previous run s Root file Duplicate trackerplane s__ Fatal Two or more trackerplane s have the same name No Trackers Fatal The trackermode command has no trackers to control Invalid Start Expr Fatal The tune command has an invalid argument Iteration Limit Fatal The tune command did not converge within the limit Invalid Tune Expr Fatal The tune command has an invalid argument Failed to Converge Fatal The tune command did no
82. G4beamline User s Guide 2 16 Tom Roberts Muons Inc tjrob muonsinc com December 2013 http g4beamline muonsinc com Copyright 2004 2013 by Tom Roberts All rights reserved See license and distribution terms in section 1 2 1 10 14 TJR G4beamline User s Guide G4beamline User s Guide Contents l TPO CUCT OM 5420 scs42ctacltaeshacssetinteabacsacashanoueesseansanh etanta above kaara one ae aina ra beg AE aa a Tal Quick Start Guideen na ien en OE EE es 1 2 License and ENTS POUCH E ic cot dalecu eae Ge echcastens an a ee ane eaten a 2 BASIC Concepts seie ee cect ices alias e tds aca AE ad aca bails T ante onde Pon hasan pak tiates Mansel 2 1 Particle tracking in simulations 3 44 05 csswererasanesd Mevducressstosd Argues wateaans Cav cnaw ic tese Aaeounnaen aati PA MORNE ia ate Ma acre a ng atte hat cen acct es Madan de Soe at A traded asa 23 ERT COMICUE YS aie ae E cous et eg asta AEA iat ae sa ak oS la it E hate a Aaa al hae Oe ZA Cordiales oe an aara E enyusd Ada ane a a ines Dido ROTATIONS se os mn a r E O e E T E a A a E 2 0 IUCN S it teeth Seta ra et Sate aa A a a a ies otal he Alain Tae 2 1 Electromagnetic Fields Geeta la 8 oaceenye a acaeinctech a e va A E A odes te atanin ya es wens 28 Visualization onne E AER ENES ts RNA a AA E AEA ENTE aA AEE EEOSE ATA E EEAS legs 2 9 Obtaining Results Virtual Detectors and other NTuples cecceecceseesreeseeeeeeeeeeseceseeeeeneeeeees 2 10 Random Number Genera
83. G4beamline will run in tracking mode In visualization mode any NTuples defined in the input file will not be written to files The simplest and most common way to invoke visualization mode is to put an argument viewer best onto the command line or select a viewer in the GUI See section 2 8 for a list of the supported visualization drivers A very useful trick is to run G4beamline interactively just to issue help and list commands g4bl cmd help cmd help beam cmd list materials You may find it useful to keep this open in one window while you edit your input file in another window Another useful trick is to add stepping Verbose 1 to the command line This will print one line per physics step so you can see precisely what happens during the simulation This is very verbose so you want to limit the number of events to some small number or type C to stop it The prints are about 120 characters wide by default so it s best to do this in a wide window You can change the information printed see section 3 2 1 A large number of useful tips and techniques are described in section 7 1 1 4 The HistoRoot Program NOTE The G4beamline distributions no longer include HistoRoot It is available at http historoot muonsinc com 1 10 14 TJR G4beamline User s Guide 9 HistoRoot is a program to generate Root plots and histograms from Root and ASCII files containing NTuples While everything HistoRoot does can be done via Root co
84. Guide 28 easily be relaxed No aspect of the geometry can be tuned via the Tune particle Note this also does not include tuning quadrupoles to achieve a specified focus because that would require tracking many beam particles and tuning to achieve a specified distribution Because g4beamline can be easily scripted however it is possible to do this manually via scripts or an external program Such an external method can tune any parameter or argument to any element including geometry See sections 7 18 and 7 21 for details Examples The program triplet sh in the examples directory focuses a quad triplet for a point to point focus In the test directory test29 test30 test31 test32 and test35 verify the tuning of each of the above quantities 2 12 The Geant4 User Interface Geant4 has its own command line processing and user interface For the most part this is not used in G4beamline Some Geant4 commands can be simply placed in the input file because all input lines beginning with are interpreted as Geant4 commands they are executed immediately upon being encountered in the input file In most cases that is not what is needed because the commands must be deferred until the geometry has been set up see the g4ui command for that The viewer def file contains Geant4 commands used to initialize and use the various visualization drivers The selected section is automatically invoked when visualization is specified via the viewer
85. INE GY EPTANE N HE XANE E GLYCE M OXYB DE LEAD UM FLUO TET I S P ROMIDE LANTHANUM AMIDE LITHIUM CARBONATE L IODIDE LITHIUM OXIDE LITH ARBONATE MAGNESIUM ETRABORATE MERCU RABO E MAGNESI ETHANE zj Es J lza H H THIUM_HYD UNG ICRP M3 OXID KAPTON RI t w AHO EL _ST ROSE MUSCLE ETAL H SUCROSE MUSCLE Z NYLON 11 POLYCARB PLASTIC SC_VINYLTOLU POLYOXYM ENE NITROUS OXIDE RILSAN OCTANE PA ENE PLUTONIUM ROSTYRENE earl ENE N 6 10 EMULSION RYLONITRILE MYLAR PL T EXIGLASS N DIOXID Y ONATE POLYCHLO ETHYLENE POLYPROPYLI REN POLYTRI POLYVINY POLYVINY Em F LUOROCHLOROETHYLENE ACETATE EFLON POLYVINYL ALCOHOL RIDI GI DE WAX MIX D WAX E POLYVINYLID TNT ENE L BUTYRAL POLYVINYL LIDENE FLUORIDE POLYVINYL RROLIDONE POTASSIU RUBBER_B ILVER B KIN ICR ODIUM N TETRACHL S S S M OXIDE PROPANE 1PROPANE UTYL RUBBER NATURAL RUBBER _ ROMIDE R CHLORIDE PYL ALCOH ENE SILVE ES POTASSI OL SILICON_ SILVER PY UM CARI P SODI BONATE SODI ITRATE STILBENE SUCROSE OROETHYLENE THALLIUM C
86. Method must be used to determine the global BASE timing of 0 RF For most applications timeMethod maxE is preferred in which the time of maximum energy gain of a positive particle is taken to be 90 RF The default timeMethod atZ emulates the old rfdevice behavior in which timeOffset is chosen such that w t timeOffset phaseAcc at the timingAtZ usually the rfdevice center location In most cases the maxStep ought to be set to 1 mm as the default step size is too large The method launches Tune Event 2 particles and uses them to find a solution The timing of deflecting cavities is discussed in section 8 6 rfdevice timingMethod maxE maxStep 1 1 10 14 TJR G4beamline User s Guide 142 maxGradient AV L MV m phaseAcc 9 degRF maxGradient AV L MV m fixEnergyGain AE MeV maxGradient AV L MV m fixMomentum Pour MeV c timeOffset tabsolute NS maxGradient AV L MV m Common phase setting option combinations The arguments to the rfdevice command are described in section 5 and section 8 6 describes setting it up in more detail but briefly one can fix some parameters while the rfdevice routine will attempt to fill in the remaining parameters if it fails G4beamline reports a fatal error The final result of the timing for each rfdevice is printed to stdout See also section 2 11 Tuning the Beamline 7 35 Tuning the maxGradient of RF Cavities rfdevice When RF cavities are used it is generally necessary
87. NTuple one file for all Root NTuples c It loops processing messages from worker nodes of which there are three basic types i A message indicating the worker is idle rank 0 responds by sending it a block of beam tracks to process sending 0 tracks if none are left ii A message containing NTuple rows rank 0 responds by writing them to the appropriate NTuple file iii A message indicating the worker took an exception rank 0 prints it throttled as usual for many identical exceptions If the exception is fatal that is communicated to all worker nodes and the program terminates gracefully d When all events have been processed and all worker nodes have indicated they have exited rank 0 terminates 5 The instances with rank gt 0 do the following Reads input file constructs the geometry the physics list etc Configures all NTuples to send their rows to rank 0 rather than writing to any file Sends a message to rank 0 indicating it is idle Waits for a message from rank 0 containing a block of beam tracks to process If the message contains 0 beam tracks sends any un sent NTuple rows to rank 0 i e flushing their buffers and then exits f Otherwise processes the received beam tracks Loops back to c Error and exception handling is not mentioned above it significantly complicates the code G4beamline makes a valiant attempt to always closeup gracefully but when the system terminates the job that may not be possible Re
88. RED viewer Java Wired Wired Offline Synonym for HepRepFile Wired3 Wired3 Offline Synonym for HepRepFile Ray Tracer RayTracer Offline Generates JPEG files use any image viewer for them VRMLIFILE VRMLIFILE Offline Use a VRML viewer VRML2FILE VRML2FILE Offline Use a VRML viewer Interactive viewers display the simulated system and events while G4beamline is running Offline viewers write the image to a file for viewing using another program The parameter that controls visualization is called viewer and to use a given visualization driver simply add viewer best to your command line or name whichever driver you want from the list above This puts G4beamline into a mode to perform tracking and visualization rather than just tracking beam through the simulated system Visualization requires the file viewer def which contains help text and the internal Geant4 commands required to invoke the selected viewer it is a simple ASCII file with format documented in its comments viewer def is searched for in the current directory and then in the directory named in 1 10 14 TJR G4beamline User s Guide G4BL_DIR which points to the G4beamline distribution directory the file is G4BL_DIR share g4beamline viewer def The G4beamline visualizations display all events of a run in a single image some viewers consider each image to be an event but for beamlines multiple events in an image are often useful Once t
89. T SEG WT POLAR NL NEWLIN Eal particlecolor Set d before the command line and are not affected by unset rameters Last centerline Z position used updated continuously Geant4 tracking parameter ion Geant4 tracking parameter Geant4 tracking parameter Geant4 tracking parameter Geant4 tracking parameter CPU Time Limit sec Size of voxels for field computation mm Default Root NTuple output filename Output update interval events Maximum physics step size mm Minimum step size mm Format for printing steps e Set nonzero to print each step Visualization driver selected default none Limit on wall clock time in seconds 1 is infinite Material of the World volume Tolerance for Z steps mm a space or comma separated list of items toggl xtended precision 3 more digits print a gt useful to grep output step number Synonym of N X Y Z T in global coords Synonym of GLOBAL X Y Z dxdz dydz in CL coords extended precision CL kinetic energy step length Synonym of ST volume name Synonym of VOL process name magnetic field electric field 3 momentum material name event ID track ID parent ID particle name centerline coord segment number weight polarization lt newline gt Synonym of NL Synonym of NL Ei go the colors for particle tracks Arguments are of the form name 1 1 0 where name is the standard name of a particle and 1 1 0 is the R G B value de
90. TransitTime minT exit for special applications maxXdeflection maxX exit for deflecting cavities X in local rfdevice s coordinates noXdeflection noX exit for deflecting cavities X in local rfdevice s coordinates minXdeflection minX exit for deflecting cavities X in local rfdevice s coordinates maxYdeflection maxY exit for deflecting cavities Y in local rfdevice s coordinates no Ydeflection noY exit for deflecting cavities Y in local rfdevice s coordinates minYdeflection minY exit for deflecting cavities Y in local rfdevice s coordinates After the base timing is determined the RF phase section 7 20 may be explicitly set via phaseAcc or be determined by specifying maxGradient and a single fixed output quantity fixEnergyGain fixMomentum fixTransitTime fixXdeflection or fix Ydeflection the phase is then adjusted to satisfy the conditions If a fixed output quantity and the phaseAcc are set but not maxGradient both timeOffset and maxGradient will be adjusted to satisfy the requirements section 7 21 Fixed output conditions fixed output request units description 1 10 14 TJR G4beamline User s Guide 161 fixEnergyGain MeV energy gain during transit of ttmingVolume fixMomentum MeV c momentum at the exit of the timing Volume fixTransitTime ns total transit time of the timing Volume fixXdeflection deg change of direct
91. User s Guide 125 simulation you want and not some other perhaps unphysical system An important tool for this is the visualization implemented by G4beamline many errors can be found simply by looking at the system to be simulated In the command line environment you need to have an active X Windows environment i e the DISPLAY variable must be set to a valid display server On Windows this is automatic on Linux it is automatic as long as you run X windows i e bring up a GUI on a Mac you may need to run the X11 application and use an xterm window in Leopard and later OSs you can simply use a normal Terminal window as the X11 application is launched automatically when needed Then all you need do is append viewer best to your g4b command and the OpenInventor viewer will be displayed Other viewers can be used get their names by using viewer best and looking near the end of the output for a list of supported viewers In the command line environment you need to type the Geant4 command run beamOn 10 to run 10 events and display them and the system In the GUI environment simply select Viewer best Each run will be displayed in the viewer as a single image so setting events run determines how many events are shown and selecting runs is how many different runs pictures will be made In the OpenInventor viewer select File Escape to quit this image simulate the next run and display its image Other viewers can be sele
92. V c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 The following additional fields are appended for format Extended format asciiExtended and format rootExtended Bx By Bz Tesla Ex Ey Ez Megavolts meter ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Valid Formats ignore case ascii bltrackfile dummy for009 for009 dat root trackfile Extended asciiExtended rootExtended Named Arguments cannot be changed in place cmd format The NTuple format see above for list filename The filename for the NTuple file Synonym for filename require Expression which must be nonzero to include the track default 1 coordinates Coordinates global centerline or reference default c kill Set nonzero to kill tracks after entering into NTuple does not kill track if require fails 0 Define an NTuple containing multiple detectors An ntuple holds the data from multiple detectors in a single NTuple with one row entry per event or per track This permits the generation of plots that compare different detectors Up to G4beamline User s Guide 1 10 14 TJR 64 detectors can be used While
93. You can also run the GUI version g4blgui input file The default format for NTuples is now Root To create histograms from NTuples you can use Root in the usual way That is rather complicated and un obvious so you can download the HistoRoot program from http historoot muonsinc com it provides a GUI interface to Root plots and histograms For visualization the OpenInventor viewer works fine use viewer best or viewer OIX Other viewers are available TROUBLESHOOTING Here is the output of ldd on Scientific Linux Fermi 4 8 where the distribution was built showing which shared libraries are used and where they come from ldd g4beamline libGLU so 1 gt usr X11R6 lib libGLU so 1 0x0342a000 libGL so 1 gt usr X11R6 lib 1libGL so 1 0x00d72000 libXm so 3 gt usr X11R6 lib libXm so 3 0x00794000 libXpm so 4 gt usr X11R6 lib libXpm so 4 0x0065f000 libXmu so 6 gt usr X11R6 lib libXmu so 6 0x0077d000 libXt so 6 gt usr X11R6 lib libXt so 6 0x006f c000 libXext so 6 gt usr X11R6 lib libXext so 6 0x003c6000 libXll so 6 gt usr X11R6 lib 1ibX11 so 6 0x002e5000 libXi so 6 gt usr X11R6 lib libXi so 6 0x00111000 libSM so 6 gt usr X11R6 lib 1ibSM so 6 0x00416000 libICE so 6 gt usr X11R6 lib 1libICE so 6 0x003e8000 libCint so gt home tjrob G4beamline 2 14 lib libCint so 0x00de0000 libCore so gt home tjrob G4beamline 2 14 lib libCore so 0x04a22000 libMathCore so gt home tj
94. Z Interval in X between points mm Interval in Y between points mm Interval in Z between points mm type cylinder Filename to write fieldmap to Comment for fieldmap Initial value of Z mm default 0 Number of points in R Interval in R between points mm Number of points in Z Interval in Z between points mm fields at specified points Intended primarily for debugging Prints Bx By Bz in Tesla and Ex Ey Ez in MegaVolts meter Each input line is x y z t separated by spaces or commas omitted values are set to 0 0 Field Values are printed after the reference particle is tracked Only global coordinates are used Positional arguments are used as input lines before reading the inputFile G4beamline User s Guide 80 profile randomseed referenc Named Arguments inputFile Filename for reading list of points stdin outputFile Filename for output stdout exit Set nonzero to exit after printing field write beam profile information to a file This command accumulates the moments of the track distributions during the run and at the end of run prints the mean sigma emittance RMS alpha and beta Twiss parameters for the tracks Each z position generates a line in the output file Each value in z and zloop can be an expression using double constants and the usual C operators and functions NOTE This computation
95. a secondary track from a decay or interaction and is unrelated to the phenomenon of interest So be warned HistoRoot has a specific feature to display the particle types Put PDGid into the Particle Type field and whenever the NTuple is scanned to generate the plot a list of the PDGid s contained within the slider cuts will be printed with names for common particles Here is a list of common stable particle PDGid s negative for anti particle PDGid Particle PDGid Particle PDGid Particle 11 e 12 Ve 13 w 14 y 16 y 22 y 111 x 211 mi 311 K 321 K 2112 n 2212 p A much more complete list of particle IDs is in Appendix 6 7 16 Finding Example Input Files using the XXX command First look in the examples directory of the distribution see section 6 There is at least one test for every G4beamline command look in the test directory under the G4beamline installation directory You can also send an inquiry our user s forum http www muonsinc com tiki view_forum php forumId 1 You can also send email to mailto inquiries muonsinc com or to Tom Roberts the primary author of G4beamline mailto tjrob muonsinc com 7 17 Parameterizing the Input File This is a general technique applicable to many different situations Parameters in G4beamline are names that represent strings Whenever name appears in an argument to a command the current value of the parameter name w
96. ace Performed only in rank 1 to avoid duplication In ASCII format the annotations are lost blank lines between tracks and a comment giving EventID and TrackID profile Sum up over all workers at the end of the run before printing totalenergy from rank 0 printf Always prints from rank 0 via messages from workers As long as each printf command is lt 1 kByte and all print s for a single event are lt 32 kBytes the output from different events will not be intermixed but the order of events is not preserved spacecharge Collective mode is incompatible with MPI This will probably spacechargelw change in the future collective Visualization Visualization is incompatible with MPI A single build can enable both visualization and MPI but they cannot be used together Windows MPI is not supported on Windows 1 10 14 TJR G4beamline User s Guide 154 8 5 1 Signals G4beamline responds to signal SIGUSR by flushing all NTuples to disk So for a long job you can look at intermediate results G4beamline responds to signal SIGUSR2 by closing up and exiting cleanly In each worker this is detected between events This is especially useful on Hopper as SIGUSR1 and SIGUSR2 are the only signals users can send to the application all others cause immediate termination without saving results 8 5 2 Estimating how many workers to use In general if your simulation runs gt 100 events sec on a typical core then MPI wil
97. aced into My Documents G4beamline Examples My Documents gt Documents on Vista The annotated output from Example is given in Appendix 5 README txt G4beamline Examples Look at the comments in each input file Examplel g4bl ExampleN02 g4bl Implements the Geant4 example NO02 FieldLines g4bl Displays field lines for 4 solenoids Study2Cooling g4bl Four cells of the Study 2 cooling channel ca MultipleScattering g4bl 200 A simple first example Puts a Gaussian beam into 4 detectors 3 A simple simulation of multiple scattering and ionization energy loss in various materials TungstenTarget g4bl An 8 GeV proton beam on a tungsten target MICE StageVI g4bl A simulation of the MICE beamline and cooling channel in Stage VI from August 2005 Includes field maps for the bending magnets and realistic window profiles for the absorbers and most realistic example Idealized_g 2 g4bl This is the largest A simulation of an idealized version of the BNL g 2 experiment 100 polarized 3 094 GeV c mu circle in a 1 4513 while their spins precess which affects the energies of their decay e SpaceCharge g4bl A parallel A uniform B field to point quad triplet with space charge With a bunch charge of 1E10 the effects of space charge start to become visible with a bunch charge of 1E12 the focus is unrecogni
98. ad so compatibility version 0 0 0 current version 0 0 0 rpath libTree so compatibility version 0 0 0 current version 0 0 0 usr X11 lib 1libGLU 1 dylib compatibility version 1 3 0 current version 1 3 0 usr X11 lib 1libGL 1 dylib compatibility version 1 2 0 current version 1 2 0 sw lib libXm 2 dylib compatibility version 3 0 0 current version 3 1 0 usr X11 lib libXpm 4 dylib compatibility version 16 0 0 current version 16 0 0 usr X11 lib libXmu 6 dylib compatibility version 9 0 0 current version 9 0 0 usr X11 lib libxXt 6 dylib compatibility version 7 0 0 current version 7 0 0 usr X11 lib libXext 6 dylib compatibility version 11 0 0 current version 11 0 0 usr X11 lib 1ibxX11 6 dylib compatibility version 9 0 0 current version 9 0 0 usr X11 lib 1libxi 6 dylib compatibility version 7 0 0 current version 7 0 0 usr X11 lib 1ibSM 6 dylib compatibility version 7 0 0 current version 7 0 0 usr X11 lib 1libICE 6 dylib compatibility version 10 0 0 current version 10 0 0 usr lib libexpat 1l dylib compatibility version 7 0 0 current version 7 2 0 usr lib libstdc 6 dylib compatibility version 7 0 0 current version 7 9 0 usr lib libSystem B dylib compatibility version 1 0 0 current version 125 2 11 Note that libXm 2 dylib is included in the G4beamline distribution and should not be a problem If it is a problem it comes from Fink in the package lesstif the Fink implementation
99. adius Radius of cylindrical field map mm tmin Minimum value of t ns tmax Maximum value of t ns Display magnetic field lines Field lines are drawn starting within a circle specified as center and radius global coordinates the plane of the circle is normal to the B field at its center Field lines are distributed within the circle with a density inversely proportional to B While it is attempted to keep their spacing as uniform as possible there are both ambiguity and randomness involved in placing the lines within the circl Lines are placed within the circle from its center outward and if B lt minField then no more lines are placed and the actual number of lines drawn will be within a factor of 2 of the value Asking for fewer than 10 or more than 1000 lines is likely to be ineffectiv Unnamed parameters can contain specific x y z values of points to start a field line nLines is only approximate Lines are drawn in both directions starting from the plane of the circle and each half line stops when it again reaches that plane Line drawing also stops whenever B is less than minField or when it leaves the world If you are interested in field lines far outside the magnets you may need to add some object with a large value of x y and or z in order to expand the world volume With dl 1 and subdivide 10 the accuracy of their meeting is usually better than 0 1 mm after
100. ae extrusion tubs 3 from the subtraction of e2 from el and e3 can be used in further boolean operations thos L is not specified lids should intersect Note that for op subtraction any common faces element should extend at least a micron outside the first element to create a hole th subtraction Simple elements are those consisting of a single d boolean EOrUS and polycone el or can be of the first material of the first and the resulting solid if not the results are undefined the two elements should not share the subtracted second Note also that visualization of boolean solids may not work properly except for the RayTracer viewer Named Arguments Tracking is fine maxStep The maximum stepsize mm material The material of the boolean color The color of the boolean white kill Set nonzero to kill every track that enters op The boolean operation union subtraction or intersection x The x offset of element2 relative to elementl mm y The y offset of element2 relative to elementl mm Z The z offset of element2 relative to element1 mm rotation The rotation of element2 construct a box This is a direct interface to G4Box Named Arguments height width length maxStep material color kill The The The The The The Set height of the box width of the box length of the box
101. alexX Scale for X and Y mm default 1mm scaleXp Scale for dxdz and dydz radians default 0 001 scalePtot Scale for Ptot MeV default 0 Set to 0 0 if tracker cannot determine momentum scaleT Scale for t ns default 0 Set to 0 0 if tracker cannot determine tim minPz Minimum Pz for valid tracks default 10 MeV c minHits Minimum number of hits for fitting planes tolerance Track fitting tolerance mm default 0 01 mm maxIter Maximum iterations during fitting default 200 verbose O none l result 2 iterations 3 detail default 0 format Format of output NTuple filename Filename of output NTuple for009 Set nonzero to also output TrackerFit as FOROO9 Dat file Synonym for filename trackermode Sets mode for all trackers manages track fitting USAGE trackermode mode file mode can be any of true tracks true tracks normal operation fit fits tracks to previous true output both does both true and fit at once fit requires the filename argument to be the output of a previous true run filename is ignored in other modes each tracker processes all of its tracks in the file true mode simply denotes the standard G4beamline operation and the simulated tracks are taken to be the true tracks of the system the response of the tracker s to these tracks is then simulated in fit mode both tracks a true event and then a fit is peerformed in each tracker for which its first track hit
102. all trackerplane s Note that in true mode every track that hits all trackerplane s is considered but in both mode only the first track of the event can be considered In fit mode the filename argument MUST be different from the parameter histoFile because this run must not overwrite the Root file from the previous true run One trackermode command controls the mode of all trackers true 1 10 14 TJR G4beamline User s Guide 94 trackerplane 1 10 14 TJR mode is normal G4beamline operation and is the same as if no trackermode command was present Note that the geometry of the system must not change between a true run anda fit run You can however make small variations in fields to explore how errors in setting them will affect the fitted tracks The trackerplane command can simulate survey errors NOTE the trackermode command must preceed all tracker commands in the input file Named Arguments filename Filename to read for fitting tracks file Synonym for filename Construct a tracker plane A trackerplane belongs to a specific tracker and represents one measuring element of the tracker While the term wire is used a trackerplane can model any planar measuring device that measures one dimension using equally spaced detectors that are either on or off hit or not hit A trackerplane can be circular specify radius and possibly innerRadius or rectangular specify
103. all daughter volumes are visible You can change that in the Etc menu The OpenInventor driver has many more features but this should get you started It will also do animation with the hand cursor left click and drag the image letting go of the button while moving the image will continue to rotate until you left click on it works best locally 2 8 3 A Trick for Visually Scanning Events The simplest way to scan events visually is to use the g4b gui program but it can be done manually via the command line The OpenInventor driver OIX has the ability to exit the viewer and return to the Geant4 command input This can be used to quickly scan events visually To do this first create a text file called beamon txt containing a large number of identical lines run beamOn 1 run beamOn 1 run beamOn 1 Many more identical lines Then invoke g4beamline like this G4bl input file viewer best lt beamon txt Once the viewer appears it will display the first event To see the next event select the File Escape menu item This will suspend the OpenInventor viewer and the Geant4 input routine will read the next line of beamon txt that causes it to track one event and refresh the viewer with it Just keep selecting File Escape to sequence through events one at a time This is essentially what the g4blgui program does when a viewer is selected 1 10 14 TJR G4beamline User s Guide 23 2 8 4 Troubleshooting Visualization is usuall
104. allation of the complete G4beamline build environment see BUILD txt in the distribution and the doxygen documentation of the classes 2 1 Particle tracking in simulations The accuracy of a simulation of tracking particles through a system depends primarily on how realistic the simulation is This has many aspects e How closely the geometry of the simulation matches the real geometry e How accurately the real electromagnetic fields are modeled in the simulation 1 10 14 TJR G4beamline User s Guide 11 e How accurately the material properties of the real objects are modeled in the simulation e How well the modeled beam distributions match the real beam e How accurately the program tracks particles e How accurately the implementations of physical processes match the real world e Etc While G4beamline provides facilities for the user to specify most of these and gives them reasonable default values it is really the user s responsibility to ensure that the results of a simulation are accurate enough to be useful In G4beamline Geant4 particle tracking is used directly with the tracking accuracy parameters of Geant4 settable by the user see section 3 2 2 2 2 Units In G4beamline all physical sizes and dimensions are specified in millimeters just as in Geant4 Most other units are as in Geant4 except rotation angles are in degrees and EM fields are in Tesla and MegaVolts meter The units of all arguments to all commands are gi
105. ame as for g4b See section 8 5 A script to run the G4b Gui program from the command line This script manages the Geant4Data directory and files Runs the G4b Data program for installation A user command to build g4beamiline with additional user written code A script for querying the G4beamline configuration Rarely if ever run directly by users A script to create a movie See section 8 3 A script for debugging G4beamline Useful only when built from source 8 6 3 Implementation Details Each script or program must determine various aspects of the environment required to run the g4beamline program Install Directory The environment variable G4BL_DIR points to the install directory Java ROOTSYS programs use Util findG4bIDir while it is hard coded into each script The Root library works better when this is set to G4BL_DIR Physics Datasets The Geant4 physics processes need various data The g4b data script manages this as do the Java programs via Util findGeant4Data Once installed the data file in the install directory points to the directory containing the Geant4Data That directory contains a setup sh script which sets the environment variables the Geant4 library expects plus directories containing the various datasets Library Search Path On Linux and Mac OS X the lib directory contains shared libraries On 1 10 14 TJR Windows they are in bin G4beamline User s Guide 158 8 7 Setting up an rfd
106. amed Arguments height The height of the solid trapezoid mm upperWidth The upper width solid trapezoid mm lowerWidth The lowerWidth of the solid trapezoid mm Xul X position of upper left corner mm Xur X position of upper right corner mm X X position of lower left corner mm xlr X position of lower right corner mm length The length of the solid trapezoid mm maxStep The maximum stepsize in the element mm material The material of the trapezoid color The color of the trapezoid invisible kill Set nonzero to kill every track that enters Alias for tubs construct a tube or cylinder with axis along z This is a direct interface to G4Tubs which can implement a tube or cylinder either can subtend less than 360 degrees in phi Named Arguments innerRadius The inside of the tube 0 0 for cylinder mm outerRadius The outer radius of the tube or cylinder mm G4beamline User s Guide 96 tune initialPhi The initial Phi value deg 0 for all finalPhi The final Phi value deg 360 for all length The length of the tube or cylinder mm maxStep The maximum stepsize in the element mm material The material of the tube or cylinder color The color of the tube or cylinder invisible kill Set nonzero to kill every track that enters radius Synonym for outerRadius mm Tune a variable used as argument to other elements This command samples
107. amiline with or without visualization The standard output and error streams are displayed in a scrollable pane in the window This is the standard interface on Windows and Mac OS X and is available on Linux G4blData Manages the Geant4Data directory which contains the Geant4 data files necessary for the different physics lists It provides a GUI that lets the user specify the location of the directory select and download the data sets from the CERN website and unpack them into the specified destination directory 8 6 2 Scripts g4bl setup sh A script to put the G4beamline scripts into the user s PATH for the sh class of shells sh bash ksh zsh etc must be source d 1 10 14 TJR G4beamline User s Guide 157 g4bl setup csh A script to put the G4beamline scripts into the user s PATH for the csh class of g4bl g4blmpi g4blgui g4bldata g4blmake g4bl config g4blmovie g4bl_debug shells csh tesh etc must be source d This is the standard script to run G4beamline It determines the install directory from the path by which it is run It then sets up the required environment variables and runs g4beamline with or without visualization The standard output and error streams are as usual in a UNIX environment This script runs G4beamline in an MPI environment applying multiple instances of g4beamiline to a single problem Its first argument is how many instances ranks to use the remaining arguments are the s
108. amline element or just an element Every element inherently has a geometrical shape and a material some elements also have electromagnetic fields associated with them Some elements are quite simple merely defining a box or tube made of some material other are quite complex defining in detail the construction and electromagnetic fields of a complicated object such as an RF cavity Elements can often be nested inside each other any element can be placed inside another element but not all elements can act as the parent of others in general simple elements can be parents complex ones cannot most elements that generate an electromagnetic field cannot be parents The notes and help for each element describe whether or not it can be the parent to other elements This is the natural way Geant4 builds the geometry hierarchically a daughter volume is said to be placed into its mother or parent volume every element is also a volume perhaps several volumes The World volume is the ancestor of all volumes and in G4beamline the World volume automatically grows to hold everything that is placed into it In G4beamline individual elements have their own material s and when a daughter is placed inside a parent the daughter s material applies inside the daughter and the parent s material applies inside the parent outside any daughters many elements use their parent s material by default G4beamline attempts to model the s
109. an 16 expressions can be broken into multiple printf s with noNewline 1 for all but the last The following variables can be used in expressions X Y Z t Px Py Pz PDGid EventID TrackID ParentId Weight Bx By Bz Ex Ey Ez tune nonzero only for the Tune particle reference nonzero only for the Reference particle beam nonzero for any Beam particle Each value in z and zloop can be an expression using double constants and the usual C operators and functions Example printf z 0 Momentum is 3f GeV c sqrt Px Pxt Py Py Pz Pz 1000 NOTE if format begins Ptot the parsing will think it is a named argument put a space before the to avoid that error Named Arguments Z Comma separated list of Z positions for printing mm zloop Loop in z first last incr mm require logical expression for cutting default true file Output filename default gt stdout filename Synonym for file noNewline set nonzero to omit final newline coordinates Coordinates global centerline or reference default c printfield Prints E or B fields or writes FieldMap file Prints the value of the electromagnetic field components For type print prints one component of the field in a 2 d table Any coordinate plane can be printed XY ZT For type grid or type cylinder writes a file in fieldmap format Global 1 10 14 TJR G4beamline User s Guide 79 probefiel
110. ance it is rather common for a particle to take a shortcut around a bending magnet so be sure to check for this Rings are obviously subject to this Shielding can be any element with kill 1 most often box or tubs the latter is particularly convenient as it can be given a hole for the intended beam it is often convenient to set color invisible but don t do that until you have looked at it to know it is appropriately sized and placed A tubs of any radius a length of 0 01 mm or more and with kill 1 is a perfect shield i e kills every particle that hits it If you have varying magnetic fields sometimes they create a trap that can store particles for a long time 1 microsecond is a long time These are usually uninteresting but can become CPU hogs Using the maxTime argument to the trackcuts command can reduce their effect 1 10 14 TJR G4beamline User s Guide 122 An exception is a Neutrino Factory decay ring in which muons are stored but the desired beam is neutrinos The difficulty is that the far detector may be very far away which makes the World be quite large and tracking non neutrino particles is wasteful The best solution is to surround the storage ring with beam pipes and magnets having a special material that kills all particles except neutrinos As the neutrinos spread out and ones that miss the far detector are uninteresting one can separate the source and far detector by a cylinder with material Rock and surro
111. ances of G4beamline cooperating on a single simulation As one instance performs only management tasks it is usually appropriate to start one more instance than the number of available CPUs Section 8 5 has many more implementation details and suggestions 7 23 Performing a Scan of Values of Some Parameter It often happens that one wants to scan over the values of some parameter looking for maximum transmission the desired emittance at a given location or some other aspect of the beamline The idea is to parameterize the input file so the parameter can be specified on the command line and then either manually scan or write a shell script to do the scan For example Param unset VALUE 1 rest of input using SVALUE One can simply do this g4bl input file VALUE 1 01 g4bl input file VALUE 1 02 g4bl input file VALUE 1 03 g4bl input file VALUE 1 04 and keep track of the desired property If the desired property is printed to stdout e g it appears normally or via a printf command one can use grep to greatly simplify the search for its value This method gives a lot of output and it can be time consuming to scan it all for the desired property of interest So it is often better to write a short shell script to run G4beamline with VALUE passed and then grep for the desired property or otherwise compute it and just output that one item Often the command history of your shell is sufficient One can also write a simp
112. apability is to find an outlier event in some histogram determine its event number via narrow cuts in historoot and re run it with visualization to see what actually happened Note that due to their internal designs Root NTuples cannot precisely represent event numbers larger than 16 million a float with 24 bits of mantissa This does not affect the ability to handle larger datasets it just means that the event numbers will be rounded to a 24 bit mantissa ASCII formats for track NTuples do not suffer from this limitation 2 11 Tuning the Beamline Just like a real beamline a simulated beamline must be tuned to maximize transmission and achieve various desired characteristics G4beamline is not intended for the design of beamlines but rather is best used for the evaluation of them Conventional beam optics design programs can be used to determine the beamline elements and their parameters These programs however usually make approximations and ignore many subtle effects that G4beamline implements e g fringe fields non Gaussian multiple scattering tails energy loss straggling hadronic interactions in collimators and other apertures non Gaussian tails in beam profiles etc The result is that just as in the real world the design programs give only approximate values So two methods of tweaking the tune are provided 1 The reference command can tune its referenceMomentum in order to make the reference particle have a specified
113. as in Benchmark2 on hopper below for 1600 workers Another symptom of not all workers starting up would be an exception Not all Workers Contributed Data for the profile or totalenergy commands 8 5 3 MPI on Mac OS X with OpenMPI Here is the build of OpenMPI configure disable dlopen enable static disable shared disable mpi f77 disable mpi f90 prefix usr local make make install If you have other systems on a network that could be used via MPI install OpenMPI on them and configure it to use them My instance of OpenMPI only uses the cores on my machine and message passing is via shared memory After installing OpenMPI build G4beamline from source mkdir G4beamline 2 14 mpi cd G4beamline 2 14 mpi G4beamline 2 14 source configure enable mpi make 1 10 14 TJR G4beamline User s Guide 155 Note the make system must be able to find MPI on its own if mpicxx is available the Makefile uses it The program runs in single core mode with visualization via g4bl g4b gui or icon or in MPI mode via g4b mpi Using a visualization viewer in MPI mode is not supported The best performance on my Mac Pro with 4 cores is with 5 ranks and MPI IdleSleep 1 8 5 4 MPI on hopper nersc gov On Hopper you must select which compiler to use both for building and for running For G4beamline the best compiler to use is gnu module load PrgEnv gnu export CC cc CXX CC CPPFLAGS dynamic mkdir G4beamline 2 14 mpi cd
114. beamline User s Guide 91 oneNTuple Nonzero to put all traces into a single NTuple primaryOnly Nonzero to trace only primary tracks traceTune Nonzero to trace tune tracks default 1 filename Filename Ev dTrk d txt or AllTracks txt file synonym for filename require Expression which must be nonzero to trace the track default 1 coordinates Coordinates global centerline or reference default c trackcolor Alias for particlecolor trackcuts Specifies per track cuts Applied to each track before tracking and at each step Named Arguments ki List of particles to ki comma separated keep List of particles to keep kill all others killSecondaries Set nonzero to kill a secondaries kineticEnergyCut Minimum K E E to track 0 MeV kineticEnergyMax Maximum K E to track infinite MeV maxTime Maximum lab time to track 1000000 ns keepPrimaries Set nonzero to keep tracks with ParentID regardless of other tests steppingVerbose Set nonzero to print kills defaults to parameter value tracker Defines a tracker A tracker consists of several trackerplane s and can fit a track to wire hits and times in the trackerplanes This is a simple algorithm that does not handle backgrounds or multiple hits It assumes that every track hits each trackerplane at most once It is intended to be used to explore resolutions and the effects of survey errors A tracker i
115. beamline elements have been given colors in your input file and so have your particles to actually visualize the simulation you need to select a visualization driver G4beamline supports the following visualization drivers from Geant4 Descriptive Name Name Type Description best Interactive Alias for the best viewer available currently OIX OIWin32 OpenInventor OIX Interactive Renders in 3d using either solid shading with transparency or wireframe mode others and permits the easy rotation scaling and movement of the image using the mouse OpenInventor OIWin32 Interactive The name of OpenInventor on Windows OpenGLImmediateX OGLIX Interactive Basic OpenGL 3 D viewer OpenGLStoredX OGLSX Interactive Basic OpenGL 3 D viewer OpenGLImmediateXm OGLIXm Interactive Like OGLIX except has Motif widgets to permit the easy rotation scaling and movement of the image If you cannot get OpenInventor to work try this one next OpenGLStoredXm OGLSXm Interactive Like OGLSX except has Motif widgets to permit the easy rotation scaling and movement of the image ASCIITree ATree Offline A simple hierarchical description written to stdout DawnFile DAWMFILE Offline Use the DAWN viewer GAGTree GAGtree Offline Another geometry description written to stdout HepRepFile HepRepFile Offline Use the WIRED viewer Java HepRepFile HepRepXML Offline Use the WI
116. bl input file MATERIAL Cu g4bl input file MATERIAL W g4bl input file MATERIAL Be Note that in the previous example the Root output file will be overwritten each time so one must be careful to obtain all desired output from one run before starting the next A better input file will use different output files for each run param unset MATERIAL Cu param histoFile SMATERIAL output ShistoFile box Target material SMATERIAL The second param command sets the name of the Root output file to include the material this command cannot be combined with the first param command and must not have unset The output command then re directs stdout and stderr to files Cu out W out Be out etc It s best to put only param commands before the output command so all output gets re directed into the output file This can obviously be extended to as many different parameters as desired It is useful to put them all into the histoFile value perhaps separated by commas By putting the parameter values into the output filenames multiple runs can be executed in parallel in the same directory This is especially useful on a system with multiple cores or on a cluster or grid 7 18 Setting Fields of Magnets If you have a specified field for a solenoid you need to convert that into a current density as that is the argument of the solenoid command that determines the field You can compute the ampere turns required but tha
117. c 1 1 L 1 1 1600 1800 2000 2200 2400 2600 2800 3000 1600 1800 2000 2200 2400 2600 2800 3000 L 1 L L 1 1 1 1 1 z mm z mm For a multicell cavity with an even number of cells the differences are much more pronounced as the center of the cavity will usually be a node in the field map For example consider a similar 2 cell cavity again with 45 MeV c u and e For e timingMethod atZ atZlocal 0 phaseAcc 90 results in no energy gain while timingMethod atZ atZlocal 0 phaseAcc 180 gives the maximum energy gain the same as one gets using timingMethod maxE phaseAcc 90 For u the situation gets complicated but timingMethod maxE phaseAcc 90 still returns the highest energy gain 45MeVic e 2 cell cavity maxE phaseAcc 90 atZ phaseAcc 90 atZ phaseAcc 180 45MeV c mu 2 cell cavity maxE phaseAcc 90 atZ phaseAcc 90 atZ phaseAcc 180 55 maxE90 a txtref u3 6 maxE90 a txt reference u 3 6 65 atZ90 a txt reference u 3 6 J aZ90 a txt reference u 3 6 atZ180 a txt reference u 3 6 atZ180 a txt reference u 3 6 60 4 U U N N gt gt U 5p 4 U 5 5 a A N N A A 50 4 45 4 35 F 4000 4500 5000 5500 6000 6500 7000 7500 4000 4500 5000 5500 6000 6500 7000 7500 z mm z mm The old rfdevice set timing based on the middle of the cavity for backward compatibility timingMethod atZ is still the default but usually ought not to be used with fixed output options setting the maximum gradient over the RF c
118. ce NC cetri Er aa AT Ava a T E a a bins a S 171 POR Tag ah ste ae Sa Fala et i ha al a ek So ale E la i ACh ale E i tte os Mth 171 OA TS A GILAD yc ose ceases lass a aches erect a sve oe a a we cco AE as ceases EES 172 OS Window FES sax Sicns asia cea bs weana tgaelacesbauaceataanediea damounensauiateabaedeaahonyaiiasdanvaantyattonsdacsaneesqeuteantanonnadiaente 175 96 RIGOUR IES sc ak eicisi ss sccesiscathaiccsees secslw a a aaa av eae eed aw Eaa 175 TOS ACR MOW IEC OHICNIUS a cca boasatesvenenteoeed N a cei a a a n O a aA 176 Appendix RE AT Wt nas acon ec Saute a cant toad nk Sl So leuial ed chs oe ade Rel a cates tral tad 177 Appendix 2 README LiINUX Axt i eaa a a a KE vaven oath case aa N ATE E T Eaki 180 Appendix 3 README WindOws tXtisccsiss saszsavsacassineasansaesesasdasdendhsnzedccatansdcasvaneacaadatassetaavadeassaaeiaadsacens 183 Appendix 4 README MacOSX tzt seseessessesseessessssseesseossessesseosessesseosesstsseossessesseesseesosseesseosoesresseo 184 Appendix 5 Annotated Output from Example g4bl oo ceececsceeseeceeceseeeeeeeeseeeaeceseeneeeenseeesaeens 186 Appendix P rticle IDS eeo a esa el iaaa EE atnsudan a E A E baad ua dater T 190 Appendix 7 Error Messages ner an aa a a a a a a a a Gace 199 ENE EAA EEE ge AC E E R T A AE EE 201 1 10 14 TJR G4beamline User s Guide 4 1 Introduction G4beamline is a particle tracking and simulation program based on the Geant4 toolkit 1 that is specifically designed to easi
119. ce particle mu beamxX 0 beamY 0 beamZ 0 beamT 0 rotation referenceMomentum 200 beamXp 0 beamYp 0 meanMomentum 200 meanXp 0 meanYp 0 tuneZ 3 7et 21 tuneMomentum 3 7e 21 tolerance 0 001 noEfield 0 noEloss 0 box BeamVis height 100 width 100 length 0 1 maxStep 100 material Vacuum color 1 0 0 kill 0 place BeamVis copies 1 x 0 0 y 0 0 z 0 0 virtualdetector Det radius 1000 innerRadius 0 height 2000 width 2000 length 1 maxStep 100 material color 0 1 0 noSingles 0 format filename file require referenceParticle 0 coordinates Centerline kill 0 place Det copies 1 x 0 0 y 0 0 z 1000 0 rename Det place Det copies 1 x 0 0 y 0 0 z 2000 0 rename Det place Det copies 1 x 0 0 y 0 0 z 3000 0 rename Det place Det copies 1 x 0 0 y 0 0 z 4000 0 rename Det The World size is printed World size befor The final values of the parameters are printed PARAMETERS Zc1 4000 5 deltaChord 3 0 deltaIntersection 0 1 deltaOneStep 0 01 epsMax 0 05 epsMin 2 5e 7 ventTimeLimit 30 histoFile g4beamline histoUpdate 0 maxStep 100 0 minStep 0 01 F STEP VOL PROCI incrementing by 201 357 mm T ESS steppingFormat N GLOBAL CL KE steppingVerbose 0 viewer none worldMaterial Vacuum zTolerance 2 0 Now a line for the construction of each Element is printed BLCMDbox Construct BeamVis parent relZ 0 0 zmin 0 1 zmax 0 1 globz 0 0 2000 0 H 2000 0 W 8001 0 L BLCMDvir BLCMDvi
120. ckground color F3F3F3 light gray Changeable in other commands borderColor The color of the borders between panes COCOC0 borderSize The size of the borders in pixels 5 marker The marker to use 21 the square marker This marker is used for all particles but see the particle command below to color them Note that other markers such as 20 filled circle can greatly slow down the movie production markerSize The relative size of the marker 1 0 1 10 14 TJR G4beamline User s Guide 148 pictureType The extension of the pictures used to generate the movie jpg Other types known to both Root and ffmpeg can be used but jpg has given the best performance particle Sets the color for each particle type Arguments are of the form 13 0000FF where 13 is the PDGid of the particle and 0000FF is the color 6 hex digits 2 each for red green and blue 000000 is black FFFFFF is white and 0000FF is bright blue The is required PDGid 0 applies to all unset particles defaults to black plot Displays a plot of two expressions filename The name of the Root file to use If omitted uses the most recently opened Root file i e from the previous command Note the NTuple names to use are fixed Movie Reference and Movie Tracks title Title of the plot defaults to y vs x where x and y a
121. cle proton the target is a tungsten rod 20 cm long and 1 cm in diameter make it red cylinder Target outerRadius 5 length 200 material W color 1 0 0 place Target z 200 These three virtualdetector s catch everything that comes out except for 1 10 14 TJR G4beamline User s Guide 105 a 1mm hole for the incoming beam Note the 0 5 mm clearance at each end of the target and the 201 mm length of the cylinder to match corners This virtualdetector catches what comes out of the target to the back note the hole for the incoming beam make it yellow virtualdetector DetBackward innerRadius 0 5 radius 1000 length 1 color 1 1 0 place DetBackward z 99 This virtualdetector catches what comes out of the target to the side one meter away make it blue virtualdetector DetSideways innerRadius 1000 radius 1001 length 201 color 0 0 1 place DetSideways z 200 This virtualdetector catches what comes out of the target in the forward direction make it green virtualdetector DetForward radius 1000 length 1 color 0 1 0 place DetForward z 301 6 7 MICE_StageVI g4bl MICE StageVI g4bl 2 5 2006 TJR This is an old model of MICE Stage VI as of Aug05 Command line parameters optional default as follows first 0 last 1000 viewer none NOTES A dp p 2 5 is only 11 MeV c which seems WAY too small old value was 75 MeV c tests show we need 17 MeV c The MICE beamline is from bmdata_
122. ct made of this material The arguments relevant to this are keep kill and require keep and kill are lists of particle names but require is an expression in terms of track variables so quite complex filters can be constructed For example in a simulation of a neutrino source it may be desirable to kill every non neutrino track that hits a magnet or beam pipe but let the neutrinos through to a detector far away By defining the material Iron as below and then using it as the ironMaterial of all magnets and the material of all beam pipes only the neutrinos can escape This way you can have a very large world including a distant neutrino detector and not waste time simulating uninteresting interactions in magnets or beam pipes or tracking uninteresting particles over long distances material Iron Fe 1 0 keep nu_mu anti_nu_mu nu_e anti_ nu e 1 10 14 TJR G4beamline User s Guide 17 2 7 Electromagnetic Fields In the real world electromagnetic fields are generated by real structures This is also true in G4beamline where various elements include their electromagnetic fields So a genericbend object includes not only the geometric shape of its iron and coils it also includes its magnetic field Placing a genericbend element into the world places both its iron and its field any rotations or offsets used in the place command apply to both the iron and the field As G4beamline is intended to model beamlines in many cases the field of a
123. cted by selecting and setting Other To save the image into a file some viewers have a File menu item that can save in various formats e g OpenInventor can save as PostScript In any viewer you can take a screenshot of the viewer window and save it to a file e Windows Ctrl PrtScrn followed by running a program to save the Clipboard in a graphics format e g Paint e Linux a program like ksnapshot e Mac OS X the Grab utility menu Capture the Preview utility menu File Grab or type shift command 4 and select the desired region of the screen Note that screenshots all save a bitmap but for viewers that implement it the File Save menu item can generate a vector file that is smaller and scales better 7 14Warning and Error messages Which Ones can be ignored G4beamline errors are all unified within the Geant4 G4Exception framework This gives them a common look and ensures that in a MPI environment they are all tabulated in rank 0 and summarized at the end of the job Errors in the input file generate an error message immediately while reading and listing the input file They must be fixed before the simulation will run These are such things as syntax errors invalid parameter names invalid arguments to commands etc Errors and warnings generated during execution are handled by the G4Exception function they are printed as a 6 line message starting and ending with a row of asterisks that makes them stand out visually in a
124. ction 3 on important values that affect the accuracy and section 7 on tips and techniques 1 1 1 Installation NOTE The G4beamline distributions no longer include the HistoRoot program It is available at http historoot muonsinc com G4beamline requires the Geant4 data needed by the physics list used in the simulation These data are placed into a directory named Geant4Data that is normally located in the user s HOME directory The first time you run G4beamline a Java program is run to assist you in downloading these data If you did not download all data initially and find you need other components later you can access the download assistant from the Help page of the GUI or by running g4bldata install 1 1 1 1 Windows Prerequisites e Java SE Runtime Environment 1 5 or later http java sun com if you have the JDK installed that includes the runtime environment e Root 1 24 or later http root cern ch Root is not required if you will use only ASCII output files though you will probably find the HistoRoot program useful to generate plots of Root and ASCII files and it requires a specific version of Root The distribution file is G4beamline VERSION msi available from http g4beamline muonsinc com Simply download it and execute it with administrator privileges By default it will install files into C Program Files MuonsInc G4beamline and place icons onto your Desktop and into the Start menu
125. d 1 10 14 TJR coordinates are used Units are Tesla for B and MV meter for NOTE This command cannot handle time dependency in the output BLFieldMap file but can in the printout ts Note if you want to plot field vs position or time the fieldntuple the 2 d paper command is probably better as it is not limited to is easier to use and lets you use existing NTuple plotting tools If you just want to test a few points the probefield command lets you do that interactively Named Arguments type exit Arguments for field layout ncol Arguments for file comment X0 YO ZO nX nY nz dx dy dz Arguments for file comment ZO nR dR nZ dz Prints B and E print grid or cylinder Set nonzero to exit after printing field type print The field to print Bx By Bz Ex Ey Ez Btot Etot Layout RowCol 2 chars AB each of xyzt The starting value of x mm The starting value of y mm The starting value of z mm The starting value of time ns The incr between points in each row mm ns The incr between points in each column mm ns The number of rows The number of columns type grid Filename to write fieldmap to Comment for fieldmap Initial value of X mm default 0 Initial value of Y mm default 0 Initial value of Z mm default 0 Number of points in X Number of points in Y Number of points in
126. d histograms and can waste CPU time on irrelevant particles Probably the best and simplest approach is to use the radiusCut argument to the start corner and cornerarc commands This puts a virtual cylinder around the centerline of the beamline killing all particles that exceed the current radiusCut You may need to use an unusually large radiusCut inside a bending magnet paired with a cornerarc so be sure to check this visually If everything within the radius Cut is either the beam aperture or elements with kill 1 then this will ensure that unusual paths outside the nominal beam aperture only extend between elements which is usually sufficient Make sure the elements fill the radius Cut or particles could go around them Note that a corner without object or rotation can be used to change the radiusCut at a specified value of z centerline coordinates Another common approach is to use the kill 1 argument to bending magnets quadrupole magnets beam pipes etc This makes them kill any particles that hit their solid parts providing shielding for many situations You can add specific objects just for shielding such as a box cylinder or tubs If you enclose the entire beamline with elements and pipes having kill 1 this is probably sufficient In many cases the beam pipes are not of interest in a simulation and putting them in is often more effort than it is worth Then you must take care that particles do not take unintended paths For inst
127. d into it Coordinates got lost Event Internal coding error Stuck Track Track A track has taken gt 100 steps without moving significantly This is usually a very low energy track on a boundary Event time limit Event Simulating the event has taken more real time than the parameter eventTimeLimit Erroneous call to Fatal Internal coding error Cannot find NTuple Fatal NTuple name not found in Root file Cannot run beam Fatal Internal coding error Geometry not closed Fatal Internal coding error Cannot read viewers def Fatal Visualization requested but cannot find the file viewers def that defines the viewers it is normally in the G4beamline install directory Viewer not defined Fatal A viewer was requested that does not exist Large Primary TrackID Warning A beam track was read with TrackID gt 1000 which can be confused with new secondary tracks having such TrackID s See section 7 14 1 10 14 TJR G4beamline User s Guide 200 References 1 Geant4 http geant4 cern ch 2 CLHEP http proj clhep web cern ch proj clhep 3 HistoScope http fermitools fnal gov abstracts histoscope abstract html 4 The MICE Collaboration http mice iit edu 5 Root http root cern ch 6 Beam simulation tools for GEANT4 and neutrino source applications hep ex 0210057 7 Cygwin http www cygwin com 8 ffmpeg http www ffmpeg org 9 Coi
128. d line you need to put the G4beamline programs into your PATH source Applications G4beamline app Contents Resources bin g4bl setup sh This can be put into your S HOME bash profile There is also g4bl setup csh Once g4beamline has been put into your PATH to run G4beamline simply do cd wherever g4bl input file name value You can also run the Graphical User Interface g4blgui input file The default format for NTuples is now Root To create histograms from NTuples you can use Root in the usual way That is rather complicated and un obvious but you can download the HistoRoot program from http historoot muonsinc com it provides a GUI interface to Root plots and histograms For visualization the OpenInventor viewer works fine use viewer best or viewer OIX Other viewers are available 1 10 14 TJR G4beamline User s Guide 184 TROUBLESHOOTING Here is the result of otool L on Mac OS X 10 6 8 Intel This shows what shared libraries are used Libraries in usr are from the OS those in sw are from Fink otool L g4beamline g4beamline rpath libCint so compatibility version 0 0 0 current version 0 0 0 rpath libCore so compatibility version 0 0 0 current version 0 0 0 rpath libMathCore so compatibility version 0 0 0 current version 0 0 0 rpath libNet so compatibility version 0 0 0 current version 0 0 0 rpath libRIO so compatibility version 0 0 0 current version 0 0 0 rpath libThre
129. d or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 2 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details http www gnu org copyleft gpl html GENERAL The general reference for G4beamline is the User s Guide located in the doc directory named G4beamlineUsersGuide pdf It is also available on the web http g4beamline muonsinc com INSTALLATION There is a Quick Start section in the User s Guide For details see the README txt file for your OS appendices of the User s Guide INITIAL TESTING Be sure you have added the G4beamline programs to your PATH see README txt Execute the following commands in a Cygwin shell on Windows source G4beamline VERSION bin g4bl setup sh cd G4beamline VERSION test loop This will run a series of tests with 1 line of description for each hopefully ending with All Tests Passed and starting over If this fails 1 10 14 TJR G4beamline User s Guide 177 see README txt for a description of what is required to run G4beamline For further assistance you can join the G4beamline forum at http g4beamline muonsinc com NOTE On Windows you will need to setup the Cygwin environ
130. d radius So it has no solid associated with it and is invisible Named Arguments radius The radius of the field region mm length The length of the field region mm n Order of helical harmonic i e n 1 for dipole b n 1 order derivative of the field at the center T m n 1 lambda Helix period along the Z axis mm phio The phase of the XY field at the entrance rad provides interactive help G4beamline User s Guide 63 idealsectorbe if 1 10 14 TJR help with no arguments lists all commands more d for all commands tailed help on that command exit after printing the help The field hep nd construct an ideal sector bending magnet help command gives detailed help gives If the first argument is exit the program will region is a sector with By specified Unlike most Elements the front around Y around the centerline Z immediately by a cornerarc the position of th face of its field angle lt 0O bends right This el A aperture idealsectorbend is the center of angle gt 0 bends to the left The only useful rotations are ement should normally be followed No fringe fields are implemented Note that there is no field inside the gross tracking errors for particles in the iron kill 1 is desirable Named Arguments Tunable angle Angle of bend degrees fieldCenterRadius Center radius of fi
131. d to the nearest millimeter Note that the zntup e can span multiple physical volumes while the virtualdetector cannot e A timentuple samples the tracks at a specified time e A newparticlentuple samples tracks when they are created e A beamlossntuple samples tracks as they are killed e An ntuple is a collection of the data for one or more other NTuple s with each row of the NTuple being a single event or track and the columns being the union of all included NTuple s in order Any NTuple generated by any of the above commands including ntuple itself can be included in this NTuple as long as the other commands precede this one in the input file e lt A trace is an NTuple generated for a single track The rows of the NTuple are the series of steps taken by tracking and the columns are the same as for a virtualdetector plus the electromagnetic fields B and E Each track is a single NTuple a separate file in ASCII formats Normally each virtualdetector generates an NTuple for its hits singles as does zntuple The ntuple command can be used to combine multiple virtualdetector and zntuple data into a single NTuple with each row of the NTuple containing all data for a single event if multiple tracks of the event hit a given virtualdetector or zntuple only the first is kept in the NTuple By default all NTuples are written to a single Root 5 output file A Root based histogramming program HistoRoot is available from http historo
132. dSolid A simple polygon in the X Y plane is extruded along z with optional scales in XY at the two ends which generate a linear scaling along z a The polygon must be simple no two sides intersect no two vertices ar qual The vertices are listed starting from any vertex and traversing the polygon in either direction without lifting the pencil from the paper Geant4 requires the traversal to be clockwise but this element internally reverses it if required For an N sided polygon give N vertices a side will be added from last to first to close the polygon N is determined by counting the entries in the vertices argument Note that while you cannot make an extrusion with a hole you can make such an object in two parts or by placing a daughter volume in this one Note the position placed is x 0 y 0 z 0 which is centered along z but need not be near the center of the polygon in XY With scalel scale2 this is not really an extrusion by making one of them 0 001 or so you can construct a sharp apex Any x or y value in vertices can be an expression using double constants and the usual C operators and functions G4beamline User s Guide 56 fieldexpr 1 10 14 TJR Named Arguments cannot be changed in place cmd length Length of the extrusion mm vertices List of vertices of the XY polygon mm x0 y0 xl yl a line from last to first
133. default constructor When properly written simply compiling your MyCommana cc via g4blmake will enable its command to be used in any input file e Because commands are so modular multiple developers can be working on multiple commands in parallel without conflicts Only modifications to infrastructure classes require coordination e Contributing a command to the G4beamline distribution is very simple and consists merely of having the development team test it and then copy its source file into the build directory e An exception to using a command is usertrackfilter This command was specifically designed to use simplified user supplied code See section 8 4 7 33 Displaying Magnetic Field Lines The fieldlines command will display magnetic field lines Due to the difficulty of finding fields without user assistance you must specify a point in global coordinates near which to start the field lines this point is used as the center of a circle of specified radius The plane of the circle is normal to the B field at its center Within the circle field lines are placed with density that is inversely proportional to B You must also specify the approximate number of field lines to draw due to the algorithm used this is only approximate Within the circle the initial points of the field lines are allocated as follows an NxN square grid is placed so it circumscribes the circle initially all points outside the circle are excluded An initial va
134. detector is used in this description any existing NTuple can be used generated by any command such as virtualdetector zntuple beamlossntuple timentuple and newparticlentuple There are two ways the detectors can be combined the default method is to construct a new NTuple that combines the fields of all the detectors each prepended with the detector name If union l1 is given then all detectors must have the same list of fields and that list is used for this NTuple any hit in any detector is simply copied to this NTuple this permits multiple detectors to be combined into a single NTuple you may want noSingles 1 for the detectors With union 1 the required veto and minHit arguments cannot be used By default an entry in this ntuple is made for each event satisfying the require veto and minHit conditions if perTrack 1 then an entry is made for each track that satisfies the require veto and minHit conditions Any hit in any detector matching the patterns in veto will prevent th vent track from being entered into the ntuple If multiple hits occur in a given detector during the event or track only the first one is kept in this ntuple Detectors are specified by patterns identical to UNIX file matching so Det matches any detector with Det anywhere in its name etc The required argument permits events to be omitted unless all of the matching detectors were hit at least once in th
135. dient corresponding to the map default 1 0 normE A normalization factor for E components default 1 0 normB A normalization factor for B components default 1 0 a Two types of maps are implemented grid and cylinder grid maps are a 3 D grid with each block of data being a single X Y plane within a block the lines are Y and the columns of each line are values along X The grid command has the following arguments X0 The X value for the first value in each line YO The Y value for the first line in each block ZO The Z value for the first block of each field component nX The number of columns per line nY The number of lines per block nZ The number of blocks per field component aX The X increment between values in each line dy The Y increment between lines dz The Z increment between blocks tolerance The tolerance for pointwise data default 0 01 mm After the grid command the following optional commands can be given extendX flip extendY flip extendZ flip These commands permit a half map to be extended to the full map around X 0 Y 0 or Z 0 respectively The optional flip argument is a comma separated list of field components whose signs will be inverted for negative values of the coordinate For example extendZ flip Bx Ex means the map from Z 0 to Z nZ 1 dZ is extended symmetrically around Z 0 to negative Z values flipping the signs of Bx and Ex when Z lt 0 This could be followed
136. e b The movie command must be included Note that once you have a working simulation this can be given on the command line g4bl input file movie 3 g4blmovie command line program a Itis included in the G4beamline distribution 1 16 and later oop 1 10 14 TJR G4beamline User s Guide 147 b Note that so far this has been used only on Mac OS X it is expected to work on other platforms but has not yet been tested The basic approach is to first run a G4beamline simulation with the input file containing the movie command and with a Root output file The movie command arranges to generate several NTuples in the Root file that will be plotted to make the movie This is quite similar to the trace command that traces all tracks into a single NTuple so the output file can grow quite large Note that a movie containing more than a few hundred particles tends to be so crowded that details are not visible Once the simulation is complete the g4b movie command is run which has its own input file to describe the movie This program uses Root to read the movie NTuples and generate a series of image files it then runs ffmpeg to convert them into the desired movie and then deletes the image files Note that movies can get large and the production process requires about triple the disk space of the final movie a 10 second movie at 24 frames second is typically about a megabyte long these rather un natural images don t compress very well
137. e By default this compiles cc cpp C into a new build of G4beamline Add v to display the details If you need an additional library list all of the files you need on the command line G4blmake v cc some other library a You can put the corresponding I some other include dir either in the environment variable CPPFLAGS or directly on the g4b make command line before the cc files that use it If you have some Fortran source then you will need a Fortran compiler that is compatible with the C compiler on your system You will also have to write the C that calls the Fortran routine s correctly functions are extern C in lower case with an underscore appended scalar arguments are passed by reference multiple array indexes are in different order etc Google C calling Fortran for suggestions In this case it is easiest to construct a Makefile to build the pieces this uses the system f o rule to compile the file fortran f then link it into G4beamline Makefile Compile cc and fortran f into G4beamline g4beamline cc hh fortran o g4blmake cc fortran o usr local lib libgfortran a clean rm f o0 g4beamline Once your private build of G4beamline succeeds to run it just follow the directions g4b make printed export G4BEAMLINE pwd g4beamline Now the g4bl script will run your private version You can verify this by looking at the heading that g4beamiline prints out duri
138. e not a bug and using the OpenInventor viewer to examine the system from different angles can give a good understanding of the field lines 7 34 Setting the Phase of RF Cavities rfdevice A rfdevice may describe either just single RF cell or a whole multicell RF structure which shares a common RF phase It is important to note that G4beamline defines 0 RF to be the rising slope of the zero crossing of the RF waveform so 90 RF is on crest for a positive particle This is a common but not universal convention The phase of an RF device rfdevice may be set in a number of ways The timing process is local to a single rfdevice tuning uses other elements to adjust parameters Timing is done first and is described here while tuning is described in the next section Examples and many details on timing RF cavities are given in section 8 6 this is just a very brief summary The most basic way to time an RF cavity is to explicitly set its timeOffset the absolute time by which the fields are translated timeOffset includes all phase information The electric field is of the form E x y z sin t timeOffset and the magnetic field B x y z cos t timeOffset The rfdevice will try to find a consistent solution based on what it is told both under or over specifying the system are fatal errors If both timeOffset and maxGradient are specified nothing more needs to be determined If timeOffset is unspecified a timing
139. e Passing Interface MPI is a standard interface that permits multiple jobs on multiple computer systems to cooperate in a single computation One executes a single MPI job that simulates the events specified in the input file internally it uses multiple jobs running simultaneously collecting their output into a single set of NTuples in a single Root file by default Only the tracking is parallelized but that is trivially parallelizable and the overheads are low it scales quite well to many processors depending on the details of both the system being simulated and the computer hardware On a Mac Pro running Mac OS X with 4 cores the management and communication overhead is only a few percent On a supercomputer at NERSC Hopper a large simulation can profitably use hundreds or even thousands of cores Note that MPI is not configured for the distributions of G4beamline It is too system specific for that You must install some MPI implementation and then build G4beamline from source G4beamline implements MPI when the argument enable mpi is given to configure when building the program While it is a general implementation compliant with MPI 2 it has been tested only on the following systems e Mac OS X 10 7 5 with OpenMPI 11 installed on a Mac Pro with 4 cores e The supercomputer Hopper at NERSC 12 On other systems it may be necessary to modify the g4b mpi script Using MPI on a Linux box or cluster ought to be very simi
140. e and 270 RF for a negative one For all other methods the 3 pass places the system near the method s condition and a simple search is conducted around it The search continues until the time steps are smaller than timingTolerance These are used to place the system near the timingMethoa s desired condition a simple search then adjusts the value of timingZero to satisfy the condition to the desired timingTolerance accuracy and then does a single pass for state ATWORKING_ BASE While the algorithm is working timeOffset timingZero timingPhase a If the state is ATWORKING_ BYPASS and maxGradient was fixed the state is changed to ATWORKING FINAL and a final pass is done otherwise it is changed to ATWORKING_BASE State ATWORKING_BASE just shows the path of the particle at 0 RF for verification If phaseAcc was Set it is added onto timeOffset and the state changed to ATWORK_ FINAL otherwise an estimate based on the output amplitude and phase from the first 2 passes is used to generate appropriate values for ATWORKING_ ESTIMATE After a single pass of state ATWORKING_ESTIMATE the state is changed to ATWORKING _FINETUNE and the routine searches for a nearby solution If one is found the state is changed to ATWORKING FINAL If maxGradient was a guess during the search for 0 RF the whole process is repeated from ATWORKING OFFSET using the new value of maxGradient as there may be some dependence of the phasing on the gradient In
141. e cavity mm pipeThick The thickness of the pipe wall mm wallThick The thickness of the cavity walls mm wallMat The material of all the walls Cu irisRadius The radius of the iris mm collarRadialThick The radial thickness of the collar mm collarThick The thickness of the collar along z mm winlThick The thickness of the central portion of the windows zero for no window mm winlOuterRadius The radius of the central portion of the windows mm win2Thick The thickness of the outer portion of the windows zero for no window mm winMat The material of the windows Be phaseAcc The reference phase of the cavity degrees skinDepth The skin depth mm timingTolerance Tolerance for timing tuning ns maxStep The maximum stepsize in the element mm cavityMaterial Material of cavity volume Vacuum timeOffset Time offset for cavity set via timingMethod ns timeIncrement Increment to timeOffset applied AFTER tuning ns timingMethod Method for determining the nominal timeOffset atZ maxE noE minE maxT nomT minT maxX noX minx maxY noY minyY timingAtZ Local Z location for timing mm fixMomentum Specify total output momentum MeV c fixEnergyGain Specify energy gain MeV fixTransitTime Specify transit time ns fixXdeflection Specify local output XZ angle deg fixYdeflection Specify local output YZ angle deg fixTolerance Specify allowable error on fixed setting
142. e event or track The patterns in required are applied only to detectors in the ntuple so a simple only matches detectors named in the detectors argument If union is nonzero the hits in each detector are entered into this NTuple as they occur each hit in any detector is included as a row in this NTuple All detectors must have the same fields which are used for this NTuple NOTE the name of a detector is by default the concatenation of its ancestors names before its own except World unless rename NAME was used in its place command The patterns are applied to the names of the virtualdetectors as they were placed including rename not the bare name of the virtualdetector command If rename det was used when placing the virtualdetector s you probably want a to match the or list them individually detl det2 det3 m NOTE This command does not work correctly in collective tracking mode unless union 1 Valid Formats ignore case ascii bltrackfile dummy for009 for009 dat root trackfile Named Arguments category The category of the NTuple detectors A comma separated list of detector patterns required A comma separated list of required detector patterns default G4beamline User s Guide 70 output param 1 10 14 TJR veto A comma separated list of detector patterns any hit cancels entry into the NTuple default forma
143. e fields are translated timeOffset includes all phase information The electric field is usually of the form E x y z sin t timeOffset The rfdevice s UserSteppingAction routine will try to find a consistent solution based on what it is told both under or over specifying the system are fatal errors A Tune Event 2 particle is launched from a spot near the entrance of the timingVolume for each pass within the rfdevice If explicitly specified timeOffset may not be altered by any subsequent requirement and any attempt to do so will result in an error message If unspecified timeOffset will be determined according to the set timingMethod and the subsequent requirements given to rfdevice and then finally shifted by timelncrement A method timingMethod launches multiple Tune particles Event 2 from a spot near the entrance of the timingVolume and uses them to determine the time associated with 0 RF Once that is complete a Tune particle then makes one pass at that setting Messages for each step in the procedure will be printed if timingDisplay 1 and additional messages will be shown if timingDisplay 2 The process will continue until changes in the base timing are less than an associated tolerance timeTolerance the default is 0 001 ns The tracking step size within the rfdevice ought to be set reasonably small usually 1 mm works well Several methods are provided to determine the base timing only for special cases
144. e most accelerator physics programs G4beamline includes particle decays and interactions of particles with matter This means that during a simulation new particle tracks can and usually will be created For instance whenever the beam goes through a vacuum window delta rays low energy e will be produced a beam of unstable particles will generate decay products etc In some simulations such secondaries are essential e g for a muon beam produced by pion decay but in others these 1 10 14 TJR G4beamline User s Guide 127 secondary particles are uninteresting and are merely a nuisance as perhaps are the neutrinos associated with that muon beam G4beamline has several mechanisms to let you deal with secondaries e physics doStochastics 0 will turn off all stochastic processes which has major implications but this implicitly inhibits the creation of secondaries e physics disable process will turn off specific physics processes e trackcuts killSecondaries 1 will kill all secondaries keep list will keep only those particles killing all others kill list will kill those particles e particlecolor assigns colors to different particles for the viewers Note that when generating histograms and plots you usually need to cut on PDGid the Particle Data Group s assigned ID for the particle of the track It is all too easy to look at a histogram see an outlier and wonder what is happening in many cases the outlier is merely
145. e surface The default tolerance is 0 002 mm Named Arguments nPoints The number of surface points to test per element printGeometry Set nonzero to print th ntire geometry visual Set nonzero to display the geometry test points tolerance Tolerance for inside outside tests mm begins definition of a group A group is a collection of elements that can be placed together preserving their relative positions The group is a LogicalVolume in the geant4 geometry this means that a group cannot overlap any other group or object even if the overlapping portion of the group is empty If you need to permit overlaps consider using a macro instead the define command If the group is given a length then children can be placed at specific z offsets relative to the center of the group If the group is not given a length then children can only be placed sequentially along z and the length will be computed by the endgroup command Width and height are computed from the largest child or the argument If radius is set to 0 the group will be a cylinder with radius determined by the largest width or height placed into it if gt 0 then that is the fixed radius If radius is not set then a box is used Note when placing objects into a group if the rename argument is used it should begin with a to include the group s name in the object s name otherwise there may be multiple objec
146. e volume A then if the track is in Al it can be tracked in Al even outside of A but if it comes in from the sibling or parent of A it won t enter Al until it enters A While violating the rules is risky and discouraged if you are careful they can be violated when necessary e g it is not possible or too difficult to describe the geometry correctly If the invalid intersections don t matter then they won t affect the result of the simulation They won t matter if all volumes involved have the same material and none of them is active in G4beamline that means they aren t a virtualdetector They also won t matter if the regions of intersection are in places where no particles are tracked e g far from the beamline aperture And they won t matter if either of the intersecting volumes has kill 1 The automatic geometry test in G4beamline verifies the geometry hierarchy by testing points on the surface of each element s volume verifying that each point is inside the parent volume of the element and is outside every sibling volume The points are selected to test corners first and then points are randomly distributed over the faces of the surface of the volume This is not perfect but it does catch nearly all invalid intersections Geant4 also has other methods of verifying the geometry hierarchy See the Geant4 user s manual 1 They involve shooting geantinos through the detector and verifying that the boundaries eac
147. eamline User s Guide 50 collective corner 1 10 14 TJR Monitor collective computation This command computes the means and sigmas related to the time stepping in BLRunManager global coordinates generating a TimeStep NTuple If the simulation has multiple bunches this NTuple combines them all and is thus almost useless This command can also generate field NTuple s at specified points in x y z unnamed parameters should be x y z values for monitoring E and B fields global coordinates NOTE This command must come AFTER other commands that compute collective fields otherwise stale field values will be used from the previous time step If deltaT is set gt 0 0 this command will put the RunManager into collective mode and set its deltaT otherwise the previous commands should do that and this command won t modify deltaT Named Arguments deltaT Time step 1 ns format Format of NTuples filenamePrefix Prefix of NTuple filenames Implement a corner in the centerline The centerline is bent by a rotation Every track that enters the volume also gets rotated The z value is for the corner and the front face of the volume if any If the corner is paired with a bending magnet or other mechanism to bend the beam no volume should be used NOTE This command is self placing do not use the place command it also affects all following placements and
148. ed interaction length of such procsses which is needed to compute the weight The re weighting applies to both PostStep and AtRest processes but some AtRest processes do not work with this re weighting for instance Decay works properly in PostStep for a moving particle but not for a stopped one AtRest This is related to the Geant4 limitation that exactly one process be active AtRest and exactly one step be taken Be sure to test your use of this commnd for a simple physical situation before believing its results Named Arguments particle Comma separated list of particle patterns gt all process Comma separated list of process patterns ratio Ratio of artificial to real cross section Defines an rfdevice RF cavity An rfdevice RF cavity is the basic RF element used to construct a linac The G4beamline convention is that OdegRF is the positive going zero crossing of the electric field so generally phaseAcc 90 degRF is on crest The timeOffset parameter if set fixes the overall global absolute timing of the cavity relative to time 0 of the Simulation If unspecified OdegRF is determined via the timingMethod setting The default timingMethod atZlocal defines OdegRF such that the test particle will arrive at the timingAtZ location then For longitudinal cavities timingMethod maxEnergyGain emulates how most cavities in linacs have their overall timing determined while
149. ee also section 2 8 4 on troubleshooting visualization problems A reasonably complete list of G4beamline error messages is given in Appendix 7 Here are some notes on specific exceptions Stuck Track If you track very low energy tracks lt 100 eV and have materials in your simulated world then you will probably see a number of Stuck Track exceptions that kill the track This occurs because very low energy tracks can get stuck on the surface taking many extremely small steps lt 1 micron Such tracks would really get absorbed into the material so killing the track is a reasonable thing to do Such error messages can usually be ignored unless they dominate your simulation Large Primary TrackID This exception has a specific cause and cure Remember that tracking in Geant4 and thus G4beamline will often generate secondary tracks and these must each be assigned a TrackID To minimize the collision of multiple tracks within an event having identical TrackID s secondary tracks by default have TrackIDs starting with 1001 and incrementing thereafter If the input beam file has a TrackID gt 1001 then confusion can result so this exception is issued You could edit your beam file to not have such large TrackID s or you can add the following to the beam command that reads the file secondaryTrackID 2001 This avoids the overlap and thus the exception larger values can be used if necessary 7 15 Secondary Tracks and Particles Unlik
150. efore starting to track it and at every step while tracking These can obviously affect the realism and accuracy of the simulation they also can be quite useful for weeding out extraneous information e g the neutrinos generated by pion and muon decay The cuts it can apply are Argument Name Default Description kill empty Comma separated list of particles to kill keep empty Comma separated list of particles to keep kill all others ignored if empty killSecondaries 0 Set nonzero to kill all secondaries kineticEnergyCut 0 MeV Minimum kinetic energy to track kineticEnergyMax_ Infinite MeV Maximum kinetic energy to track maxTime 1000000 ns Maximum lab time to track In addition there is a processing time limit implemented as a parameter eventTimeLimit defaults to 30 seconds This applies to the real time used during the processing of all tracks in the event For simulations in which showers are important and are not suppressed this may need to be increased Unfortunately it is implemented as a real time limit not a CPU time limit so on excessively loaded systems it may also need to be increased not usually a problem There is also a wallClockLimit that will exit the simulation gracefully when the total wall clock time exceeds its value default is infinite 1 10 14 TJR G4beamline User s Guide 33 3 6 Fringe Fields Real magnets have fringe fields and G4beamline makes an att
151. egory of the NTuple format NTuple format see above for list filename Name of file x Loop for x values Xmin Xmaz dX or X1 X2 mm y Loop for y values Ymin Ymaz dY or Y1 Y2 mm Z Loop for z values Zmin Zmaz dZ or Z1 Z2 mm E Loop for t values Tmin Tmaz dT or T1 T2 ns exit Set nonzero to exit after generating NTuple 0 G4beamline User s Guide 59 for g4ui genericbend 1 10 14 TJR file Synonym for filename For loop Syntax for ivl v2 v3 commands endfor Sets the parameter i to values vl v2 v3 and executes the commands Values can be any strings including numbers except they cannot contain an named parameter After completion i retains its last value Do s for s and multi line if s can be nested in any manner Note the for command will not work from standard input or as a command in a single line if Accesses the Geant4 user interface Each positional argument is executed as a Geant4 UI command according to the when parameter No positional arguments means open a UI session on stdout stdin For a given value of when the UI commands from all g4ui commands are executed in order Named Arguments when O before reference l before beam 2 after beam 3 cannot be used 4 visualization construct a generic bending magnet The field region is a box with By specified A fringe field computation based on the method of COSY INFINITY is included b
152. eld mm fieldInnerRadius Inner radius of field mm fieldOuterRadius Outer radius of field mm fieldHeight Height of field mm ironInnerRadius Inner radius of iron mm ironOuterRadius Outer radius of iron mm ironHeight Height of iron mm By Magnetic field Tesla fieldMaterial Material of field fieldColor Color of field ironMaterial Material of iron ironColor Color of iron maxStep The maximum stepsize in the element Ki 1 Set nonzero to kil Conditional execution of command s waren Note that 90 lt angle lt 90 degrees this can result in and implies that mm 1 particles hitting the iron Single line format if pi If the expression is true CMD1 CMD2 nonzero and if The commands usually need to be quoted Multi line format if Si CMD1 elseif i else CMD2 CMD3 endif The comma nds are executed in the usual way G4beamline User s Guide lseif else endif the commands are executed elseif and else are 64 include label lilens list 1 10 14 TJR optional but endif is mandatory Any number of elseif s and commannds can be used Do s for s and multi line if s can be nested in any manner If there are spaces in the expression it must be quoted includes a command file include requires one argument the file to include Display labels or markers visually in 3 D space
153. empt to model them The model is based on that in Cosy Infinity 13 and uses Enge functions with six parameters a4 ag z Zeige aperture if s lt 4 Enge s 1 if s gt 4 Enge s 0 Enge s 1 1 exp a ans azs ays ass ags s fringeFactor Both genericbend and genericquad have reasonable default values for these parameters The command line can set fringeFactor and fringe a az A3 A4 As A all must be real numbers The user must ensure that the parameter values result in a smooth Enge function with correct limiting behavior 3 7 Stepping and Hard Edges If your simulation has hard edge fields then beware of the interaction between the stepping during tracking and these hard edges In particular tiny changes in track parameters can have much larger effects on the tracking because one more or fewer steps occurred in the field region This can also occur for the edges of physical components as one more or fewer steps occur inside a material The effects can be minimized by setting maxStep to a small value e g 1 mm and by ensuring that every hard edge field corresponds to a geometrical boundary e g don t use openAperture 1 Usually this is not a big problem as the effects normally are both small and inherent in the monte carlo method This can be bothersome when making a detailed comparison with some other code or an analytic result 3 8 Radiative Decays Decaying particles can a
154. en elements are placed inside another element the name of the parent is prepended to the name of the placed daughter so the name shows its element hierarchy This makes it desirable to capitalize the first letter of each name The World volume name is not prepended otherwise it would apply to every element name The rename argument to the place command can be used to override the name of the element the default is without the parent s name but rename Xyz will prepend the parent s name to Xyz can be used to automatically number multiple placements see the place command in section 5 for details There are several independent name spaces used by various commands Type Defined by Used by Element names Element definition commands place command Virtualdetector names Name of the virtualdetector as placed ntuple command Material names Material command Element definition commands many materials are predefined material name argument Coil names coil command solenoid command Parameter names param command param command name 4 3 Parameters Parameters are named ASCII strings that can be used in the input file to set command arguments and some are used to control the program They can be set either on the command line or by the param command They are stored internally as ASCII strings and when they represent an integer or floating point value they are converted when used invalid values are er
155. enchmark directory of the distribution 1 10 14 TJR G4beamline User s Guide 156 Benchmark1 MICE Beamline Benchmark 2 on hopper nersc gov 9000 14000 8000 12000 0000 8000 6000 Events per second 4000 2000 oO PETTITT TTT TTT TTT TTT TTT TTT Ty a a a ap xe ero i Ne I el ie Int 40 60 80 100 200 400 600 800 1000 1200 1400 1600 nWorkers nWorkers Hopper Parallelization Graphs Benchmark and Benchmark2 8 6 G4beamline Helper Programs and Scripts G4beamline requires a large number of environment variables to be set so users rarely run the g4beamline command directly but rather execute it via a helper program or script The helper programs are all written in Java and run in all environments that G4beamline itself can run Their Java class files are located in share g4beamline of the installation The Java runtime environment JRE must be installed The helper scripts are usable in these environments 1 Linux 2 Mac OS X 3 Windows with Cygwin The scripts rely on the bash shell and are therefore not runnable on Windows alone They are located in the bin directory of the installation Note however that the Java programs provide the same functionality as the scripts except for MPI which is inherently command line 8 6 1 Helper Programs G4b Gui Provides a Graphical User Interface to G4beamline It sets up all required environment variables and runs g4be
156. enerate the map and simulation accuracy While G4beamline can make it rather simple to specify a simulation it cannot substitute for knowledge and experience about the problem domain or about particle tracking simulations in general Like all computer programs G4beamline is prone to garbage in garbage out especially when used by unskilled users It is strongly suggested that you use visualization to verify the geometry of your simulation and that a handful of particles are tracked properly through it Whenever possible you should arrange to track through a simple geometry that you can compare to independent results to make sure that what you think is happening actually does occur in the simulation 1 10 14 TJR G4beamline User s Guide 5 This document does not discuss compiling and building the G4beamline program That is an advanced topic complicated by the complexity of linking a Geant4 executable with several external libraries and diverse visualization drivers Most users will not need to do that and can just use the distribution as is The README txt and BUILD txt files in the distribution and the appendices provide considerable detail about how to build the program G4beamline release 2 16 uses Geant4 release 9 6 patch02 1 1 Quick Start Guide This section gives a quick overview of how to install and run G4beamline It cannot discuss all the subtleties involved in performing simulations New users should note in particular se
157. ength of the Detector mm maxStep The maximum stepsize in the element mm material The material of the Detector Scintillator birks The Birks constant 0 mm MeV unless known color The color of the Detector white invisible noSingles Set to 1 to omit the NTuple for singles format NTuple format see above for list filename file require f a referencePartic coordinates Coordinates global centerline reference or 1 A 5 coord kill per 1 10 14 TJR ilename uses name to determine filename lias for filename Expression which must be nonzero to include the rack default 1 le Set to 1 to include the Reference Particle ocal default local lias for coordinates et to 1 kill all tracks after entering them into NTuple s Track Set to 1 generate an entry for each track default is per event G4beamline User s Guide 54 do emfactor endgroup 1 10 14 TJR Do loop Syntax do i 1 10 1 commands enddo Sets the parameter i to values 1 2 3 10 and executes the commands The increment is 1 by default and negative increments are allowed with limits reversed do i 1 0 and do i 0 1 1 will execute no commands After completion i retains its last value Do s for s and multi line if s can be nested in any manner Note the do command will not work from standard input or as a command in a single line if
158. ependent of P These parameters can be given on the command line to explore variations P momentum of the reference and bunch center sigmaP SigmaP of the initial beam sigmaX SigmaY sigmaZ sigmaXp sigmaYp other beam parameters spacecharge parameters deltaT time step ns nGrid points in each dimension of the grid nApprox points in each dimension of the approximation maxBeta max beta in reference frome for bunch of charge distribution used for grid sizing verbose verbose print control P 200 sigmaP 0 sigmaX 20 sigmaY 20 sigmaZ 20 sigmaXp 0 sigmaYp 0 deltaT 0 100 nGrid 65 nApprox 7 maxBeta 0 1 percentile 99 verbose 0 nMP 5000 totalCharge 1 o point focus at z 6000 determined using triplet sh scaled by P QF 2 79310 SP 200 QD 4 95221 SP 200 spacecharg deltaT 0 100 charge StotalCharge S nMP dx 3 SsigmaxX dy 3 SsigmaY dz 3 SsigmaZ verbose 0 deltaT S deltaT nx SnGrid ny nGrid nz SnGrid nxApprox SnApprox nyApprox SnApprox nzApprox SnApprox maxBeta SmaxBeta percentile Spercentile verbose verbos collective param worldMaterial Vacuum beam gaussian particle mut nEvents SnMP meanMomentum SP sigmaP SsigmaP sigmaX SsigmaX sigmaY SsigmaY sigmaZ SsigmaZ sigmaXp SsigmaXp sigmaYp SsigmaYp reference particle mu referenc Momentum S P genericquad Quad fieldLength 100 ironLength 100 apertureRadius 100 ironRadius 200 kill 1 box Box height 50 width 50 length 1
159. er Note that section 4 5 of the User s Guide has a dimensioned drawing of an absorber Named Arguments cannot be changed in place cmd absWindow The name of the absorber window safetyWindow The name of the safety window insideLength Absorber length inside windows mm absMaterial The material of the absorber windowMaterial The material of the window s safetyMaterial The material inside the safety windows safetyDistance Distance between absorber and safety windows mm color The color of the absorber invisible maxStep The maximum stepsize in the element mm beam Define the Beam The beam command is beam type argl vl Types are gaussian rectangular ellipse ascii and root Gaussian beams are randomly generated to emanate from beamX beamY beamZ with the given sigmas negative sigma means flat with sigma as halfwidth Rectangular beams are randomly generated to emanate from the rectangle beamHeight by beamWidth centered at beamX beamY beamZ Ellipse beams are randomly generated on the ellipses in X Xp Y Yp T E with meanE determined from meanP and the sigmas used as half widths tracks are generated on the ellipse with uniform density when plotted with scales such that the ellipse is a circle ASCII beams are read from a file using the format specified the formats supported are BLTrackFile2 The value of
160. erenkov2 Calorimeter 6 8 Idealized_g 2 g4bl Idealized_g 2 g4bl This is an idealized simulation of the BNL g 2 experiment 3 094 GeV c mu are started with polarization 0 0 1 ina perfectly uniform B field of 1 4513 T their decay electrons are put into an NTuple for histogramming This requires hundreds of millions of events so you probably need to run it on a grid 1 10 14 TJR G4beamline User s Guide 113 or a cluster the root and out files are named for first may need to be changed on a grid param unset first 0 last 999999 set name of root and out files param histoFile Sfirst output ShistoFile out set steppingFormat to include the polarization param steppingFormat GLOBAL P KE POLAR B physics includes spin tracking keep only mu and e physics QGSP BERT spinTracking 1 trackcuts keep mu e beam is polarized beam gaussian polarization 0 0 1 particle mu meanMomentum 3094 firstEvent Sfirst lastEvent Slast NTuple for electrons newparticlentuple Electrons require PDGid 11 kill 1 B is used to expand the world to 100 meters square more than enough box B height 1 width 100000 length 100000 place B z 0 y 500 F gives the field fieldexpr F height 1000 width 100000 length 100000 By 1 4513 place F z 0 6 9 SpaceCharge g4bl SpaceCharge g4bl The beamline is a quad triplet tuned to do parallel to point focusing at z 6000mm
161. ering 1 0 eLoss Ratio for ionization energy loss fluctuations 1 0 deltaRay Probability to keep delta rays 1 0 Eloss Synonym for eLoss eloss Synonym for eLoss ends a group definition G4beamline User s Guide 55 eventcuts exit extrusion 1 10 14 TJR The group may then be placed as any other element If the group was not given a length via an argument endgroup computes the length and adjusts the offsets of all elements in the group so they refer to the center of the group Implements cuts on event number via lists in files The files are ASCII with one event number per line If the keep file is not empty only event numbers listed in it will be analyzed except those listed in the skip file The skip file lists event numbers that will be skipped and event numbers listed in both files will be skipped When reading the files lines beginning with are ignored blank lines are interpreted as event 0 Named Arguments keep The file containing a list of event numbers to analyze default is all skip The file containing a list of event numbers to skip filename Synonym for keep file Synonym for keep exit a command file The exit command ceases reading the input file and starts the simulation immediately ignoring the remainder of the input file construct a solid extrusion with axis along z This is a basic interface to G4Extrude
162. erlines G4beamline can automatically tune the field of a bending magnet but cannot tune its position So the best approach is to put the field tuning into the input file and then tune the position manually this reduces a 3 parameter manual problem to two parameters which goes much faster Once the position is correct for one reference momentum other reference momenta can be handled by simply re tuning the field or manually adjusting it Here is an example for a 60 degree left bend Param unset Zoffset 0 Xoffset 0 1 10 14 TJR G4beamline User s Guide 130 tune BlField z0 1000 z1 3000 initial 2 000 step 0 05 expr Px1 Pz1 tolerance 0 000001 place Bl z 2000 SZoffset x SXoffset rotation Y30 By BlField corner z 2000 angle 60 The basic idea is that the tune command will vary the value of B1Field and re track the tune particle from z0 1000 until it is parallel to the centerline at z1 3000 within 1 microradian tolerance The user will manually vary Zoffset and Xoffset until the magnet is properly placed so that reference particle is on the centerline at z1 3000 and is equidistant from the horizontal edges of its aperture these are not independent due to the rotation of the magnet and the presence of its fringe field both will be reasonably close to 0 within 200 mm or so Note the initial value in the tune command must be close enough so the initial tune particle actually reaches z1 3000 1 e does not hit any aperture beforehand
163. ertex array end end of input or EOF e The only requirement on order is that the vertices mentioned in a facet line must already be present in the vertex array Each The first vertex is entry 0 Named Arguments vertex is appended to the end of the vertex array for VERTEX lines large gaps in the sequence of indices will waste memory filename File to read for definition maxStep The maximum stepsize in the element mm material The material of the tessellatedsolid color The color of the tessellatedsolid invisible kill Set nonzero to kill every track that enters debug Set nonzero to display markers on surface file Synonym for filename test random number seeds Test Construct an NTuple of tracks at a specified time A time NTuple generates an NTuple of every track at a specified global time It uses a linear interpolation in the step that straddles the required time so accuracy will suffer for large steps The NTuple uses centerline coordinates if availabl The standard NTuple fields are X Y Z mm Px Py Pz MeV c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 le The following additional fields are appended for format Extended format asciiExtended and format rootExtended G4beamline User s Guide 89
164. es etc All coordinates are centerline coordinates G4beamline User s Guide 81 reweightprocess modify 1 10 14 TJR If desired the referenceMomentum will be tuned to a specific value at a later z position in the beamline by giving values for tuneZ and tuneMomentum tolerance can be set if desired Normally used in conjunction with a beam command Named Arguments particle Reference particle name beamX Reference location in X mm beamyY Reference location in Y mm beamZ Reference location in Z mm beamT Reference tim ns rotation Rotation of the beam referenceMomentum Reference particle momentum MeV c beamXp Reference particle Xp radians beamYp Reference particle Yp radians meanMomentum Synonymn for referenceMomentum meanxp Synonym for beamXp meanYp Synonym for beamYp tuneZ Z position for momentum tuning tuneMomentum Desired momentum for momentum tuning tolerance tolerance for momentum tuning 0 001 MeV c nokEfield Set nonzero to make this Tune and Reference particle not respond to E fields ICOOL style noBfield Set nonzero to make this Tune and Reference particle not respond to B fields ICOOL style noEloss Set nonzero to make this Tune and Reference particle not respond to ionization energy loss ICOOL style P Synonym for referenceMomentum the cross section of a physics process This command will modi
165. esla Ex Ey Ez Megavolts meter ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Valid Format for009 dat Named Arguments format filename file require S root trackfile ignore case ascii bltrackfile dummy for009 Extended asciiExtended rootExtended cannot be changed in place cmd The NTuple format see above for list The filename for the NTuple Synonym for filename Expression which must be nonzero to include the track default 1 7 7 G4beamline User s Guide 48 boolean box 1 10 14 TJR coordinates Construct Coordinates default c an element from This command takes a pair element initial e solid wi on that is a boolean lements intersecti Boolean th no EM fiel ssellat spher fe t The comma nd is boolean op subtraction e3 el e2 dsolid This crea e2 placed in The local coordinates of th If material element CES lement to the world element is used The two input sol should be a sing e piece global centerline or reference a boolean operation between elements of simple elements and creates a new operation between the solids of the operations are new box trap args lement ar union e
166. evice It is worth repeating that G4beamline defines 0 RF to be the rising slope of the zero crossing of the RF waveform so 90 RF is on crest for a positive particle while 270 RF is on crest for a negative one This is a common but not a universal convention For many applications especially very relativistic beams setting up the RF is very straightforward For others such as muon cooling the beams are relatively slow phase and gradient are coupled and compensating for energy loss in absorbers is the goal rather than simple acceleration There are a number of ways to setup the RF This autoTiming process is local to a single rfdevice while the tune command uses information downstream of the rfdevice A brief how to on timing the RF is in section 7 34 and adjusting the gradient using tune is in section 7 35 Everything is totally determined once timeOffset and maxGradient and the fields are known The timing process described here may be used to determine timeOffset and or maxGradient of a single RF device and may then derive phaseAcc and other quantities Inside every rfdevice is a timingVolume This object is a cylinder with one face close to the entrance and the other at the point that will be used to determine the timing almost always either at the center of the cavity the default when using timingMethod atZlocal or at the exit all other methods This timingVolume is immaterial but it is an object and ought not overlap any ot
167. for additional secondaries The trace command adds the following fields to the NTuple after the standard fields Name Description Bx By Bz The magnetic field at the track s position in the selected coordinates Tesla Ex Ey Ez The electric field at the track s position in the selected coordinates Megavolts meter The format Extended format asciiExtended or format rootExtended argument to these commands adds the following fields to the NTuple after the standard fields and the B and E fields from the trace format Name Description ProperTime The proper time of the track since it was created Nanoseconds PathLength The total path length of the track since it was created Millimeters PolX PolY PolZ The polarization of the track in the selected coordinates InitialKE The Kinetic Energy of the track when it was created MeV 2 9 2 printf The printf command generates a printout in a user specified format for every track that reaches its specified Z position the standard fields above can be used in expressions to be printed via conversion specifications in the printf format string Output can be to stdout or to a file and multiple printf s to the same file will be output to the file in the order tracks reach their Z positions and in the order the printf s appear in the input file for the same Z position This permits ASCII output of track information in any desired ASCII format per
168. fy the cross section of a physics process modifying the track weights so that weighted histograms give the same statistical result as if the command were not used Used properly this can greatly reduce the variance of the result Care should be taken to ensure that all regions that should be sampled actually are sampled For instance if ratio gt l the interaction length will be reduced and deep inside an absorber there may be no sampling because no simulated tracks ever get there even though real tracks will If ratio lt l then the upstream regions of absorbers will be under sampled this is usually OK as the desired result is to increase the sampling deep inside the absorber For ratio gt gt l this command can be used to examine rare processes This can induce multiple rare interactions in an event when normally none would b xpected the weights will still correctly correspond to the real interaction even though the event topologies don t This command cannot reweight any continuous process e g multiple scattering ionization energy loss etc it will issue a fatal exception if applied to such a process G4beamline User s Guide 82 rfdevice 1 10 14 TJR This command should not be applied to other processes that re weight tracks e g the neutrino command Indeed it probably won t give the correct weights if any such process applies to the particle except for itself it cannot determine the unmodifi
169. g Multiple scattering and ionization energy loss in materials SH He HEHE lengths are mm momentum is MeV c density is gm cm 3 physics QGSP BIC beam gaussian particle mu meanMomentum 172 nEvents 100000 trackcuts keep mut param histoFile Li material Li A 6 941 Z 3 density 0 53 tubs Target outerRadius 100 material Li length 12 78 color 1 0 0 material is Be2 because Be is already defined with slightly different density param histoFile Be material Be2 A 9 012182 Z 4 density 1 85 tubs Target outerRadius 100 material Be2 length 3 73 color 1 0 0 param histoFile H2 material H2 A 1 00794 Z 1 density 0 0755 tubs Target outerRadius 100 material H2 length 159 color 1 0 0 param histoFile C material C A 12 011 Z 6 density 1 69 tubs Target outerRadius 100 material C length 2 5 color 1 0 0 virtualdetector Det radius 1000 color 0 1 0 7 place Target z 100 place Det z 200 6 6 TungstenTarget g4bl TungstenTarget g4bl 8 GeV proton beam into a tungsten target RT Gl The default physics list is QGSP B physics QGSP_BERT the beam is 8 GeV kinetic energy the mass of a proton is 938 272 MeV c 2 param M 938 272 KE 8000 0 param P sqrt SM SKE SM SKE SM SM a zero emittance beam is unrealistic but simple it easily fits through a 1 mm hole in the backward detector It emanates from z 0 beam gaussian meanMomentum SP nEvents 1000 parti
170. guments c no iron is constructed annot be changed in place cmd fieldLength The length of the field region mm ironLength The length of the iron mm ironRadius The outer radius of the iron mm apertureRadius The radius of the aperture mm poleTipRadius The inner radius of the pole tips mm coilRadius The radius of the inside of the coil mm coilHalfwidth The halfwidth of the coil mm coilHalfWidth Synonym for coilHalfwidth gradient The magnetic field gradient dBy dx Tesla meter maxStep The maximum stepsize in the element mm ironMaterial The material of the iron region fieldMaterial The material of the field region ironColor The color of the iron region kill Set nonzero to kill tracks hitting the iron fringe Fringe field computation set to 0 to disable or a comma separated list of 6 Enge function parameters fringeFactor Fringe depth factor 1 0 openApertur Set nonzero to omit the aperture volume geometry Arranges to perform a geometry test 1 10 14 TJR G4beamline User s Guide 61 group The geometry test checks nPoints points on the surface of each element verifying that they are inside the parent element and that they are not inside any sibling element The default of 100 points is usually sufficient 0 means omit the geometry test The first 20 40 points depending on element test corners the rest are randomly distributed on th
171. h one crosses are ordered properly They can be executed using the g4ui command 8 3 Making a Movie G4beamline now supports the ability to make a movie of the beam with the camera sitting on the reference particle watching the other beam particles dance around nearby The implementation is quite flexible and permits the user to specify multiple simultaneous panes each displaying an arbitrary pair of expressions using the track variables An example movie is viewable at http g4beamline muonsinc com Here is its first frame 1 10 14 TJR G4beamline User s Guide 146 y vs x Px gs x t 0 001 ns This movie is of Example1 g4bl in which a Gaussian muon beam propagates through free space into four virtualdetector s which are invisible in the movie The movie is 10 seconds long during which the y vs x pane s particles grow considerably and the two lower panes ellipses rotate in the usual manner A handful of decay electrons and neutrinos become visible Making a movie requires the following prerequisites 1 Installation configuration requirements G4beamline version 1 16 or later Root version 5 20 or later A C compiler that Root can use in ACLiC mode You must use the command line to run g4blmovie on Windows this requires Cygwin 7 The ffmpeg program 8 must be installed it converts a series of frame images into a movie 2 G4beamline simulation requirements a There must be a reference particl
172. haps to feed directly into some other program 2 9 3 profile The profile command prints a computation of the means sigmas and emittances for all tracks at a given Z position 2 9 4 totalenergy The totalenergy command totals up the energy deposited by all tracks of a run in selected physical volumes and prints the results at the end of the run Output defaults to stdout but can be put into a file With appropriate post processing this can be used to estimate heat loads in specified volumes 1 10 14 TJR G4beamline User s Guide 26 2 10 Random Number Generator G4beamline uses the default Geant4 random number generator which is HepJamesRandom from CLHEP 2 see the CLHEP documentation for details It is an excellent pseudo random number generator that essentially guarantees no repeat sequences when seeded by any integer between 0 and 900 million At the start of each event G4beamline seeds the random number generator with the event number This permits the user to submit multiple jobs in parallel with confidence as long as the beam command arguments are arranged so no two jobs run events with the same event numbers quite effective when using a Linux cluster This also permits the user to re run the same events as long as the input file remains unchanged the slightest change can cause tracking to use a different number of random numbers and thus the runs of the same event number won t be the same A good use of this last c
173. he command line this permits the input file to set defaults that can be overridden on the command line Parameters ar xpanded only in the arguments of commands cmd argname Sparamname real valued expressions for arguments can use Sparamname as a value as long as paramname contains a valid real expression Parameters are most useful for setting global things like viewer and histoFile or as parameters used in the input file When a parameter is used if it has not been defined it will be defined from the environment if possible if it is not defined in the environment then this generates an error message The values of parameters are strings but if the value of a parameter is set to a valid real expression including at least one operator lt gt amp the parameter value will be set to the numerical value of the expression to 8 significant digits G4beamline User s Guide 71 pre defined Program control parameters listed below are NOTE defin Program control Pa Zcl deltaChord deltaIntersect deltaOneStep epsMax epsMin eventTimeLimit fieldVoxels histoFile histoUpdate maxStep minStep steppingFormat steppingVerbos viewer wallClockLimit worldMaterial zTolerance steppingFormat is EXT TAG N NSTEP GLOBAL XYZT CL CLX K 7 GI Fi EP STEPLE VOL VOLNAMI PROCESS zZ E W El Ww MAT PAR
174. he dipole magnitude at rho 0 Tesla lambda Helix period along the Z axis mm phio The phase of the XY field at the entrance deg Bsolenoid The value of Bsolenoid Tesla bQ The quadrupole magnitude at rho 0 Tesla bs The sextupole magnitude at rho 0 Tesla rr Reference radius mm psid The offset between the dipole term and the quadrupole term Degrees ez The base electric field inside the helix channel GV m helicalharmonic construct a helicalharmonic magnet help 1 10 14 TJR Creates a cylindrical region containing the field of a magnetic helical harmonic of given order n The field is defined by the value of the n 1 order derivative b of the vertical field component when the initial phase is 0 with respect to the horizontal coordinate at the center of the helix b dqd n 1 B_ phi dr n 1 r 0 amp phi k z phi0 0 where k 2 pi lambda is the helix s wave number lambda is the length of the helix s period and phi is the initial phase The field a in the cylindrical frame are given by B_phi 2 n LALN AOA Enel nt ker E PAE AKER eos phi k z phi0 Br 2 n n 1 b I n 1 n k r I nt 1 n k r sin ne phi oa Buzi 28 2 n 1 b I n n k r cos n phi k z phi0 where I n x a na modified Bessel function of the first kind of order n Note that this Element generates magnetic field only and only within the cylinder defined by length an
175. he entire value must be enclosed in single or double quotes this delimiter cannot appear in the value Any argument that is not named is positional and its value can also be enclosed in single or double quotes positional arguments are conventionally given first but can be intermixed with named arguments The order of positional arguments is important but the order of named arguments is not This command has 2 named arguments param histoFile histoscope hst histoInterval 100000 This command has 1 positional and 4 named arguments tubs Target outerRadius 10 length 100 material W color 1 1 1 This command has 3 positional arguments the last 2 are each themselves a command that will be invoked when the defined command MyMacro is used define MyMacro tubs 1 outerRadius 10 length 100 material 2 color S3 place 1 That macro is used like this MyMacro TubsName Fe 1 0 1 Command files can be nested see the include command Simple macros can be defined with arguments see the define command The value of a named or positional argument can come from a parameter by using a param H 10 0 W 20 0 L 30 0 box BoxName width SW height SH length SL Note that parameter substitution occurs only within the value of a parameter this can be combined with arithmetic expressions for numeric arguments box Box H W L width SW 10 height SH 2 0 length sqrt SL 1 10 14 TJR G4beamline User s Guide 36 The pa
176. he viewer has been selected if you are running g4beamline manually you need to start a run by waiting for the idle gt prompt and then typing run beamOn 23 or however many events you want to display When G4beamline presents you with an idle gt prompt this is the Geant4 internal command processor Viewer def uses these commands to setup and invoke the selected visualization driver and to arrange for tracks to appear in the images See the Geant4 User s Guide 1 for details about these commands Typing either exit or C Ctrl C will terminate the program The idle gt prompt appears after the commands in viewer def have been executed and the visualization viewer is set up If you are finished simply exit the program C or issue run beamOn 23 to run the next 23 events and visualize them i e generate another image containing those events The Offline drivers are smart enough to generate a new image file for every beamOn command filenames vary for each driver The g4b gui graphical user interface program automatically handles all this If your input file has no beam or reference commands you can visualize the system without any events simply by setting viewer best or other viewer on the command line 2 8 1 Additional Visualization Techniques These techniques use the Geant4 user interface via the g4ui command You may want to look at the Geant4 help for these commands to do so go to the examples
177. her object It will be visible in the graphics if timingDisplay is nonzero rfdevice RF1 innerLength 744 color 0 8 0 0 8 0 4 fregquency 0 20125 maxGradient 25 phaseAcc 70 innerRadius 450 pipeThick 1 wallThick 1 irisRadius 230 collarRadialThick 0 collarThick 0 winlThick 0 win2Thick 0 winMat Vacuum winMat Vacuum cavityMaterial Vacuum maxStep 1 timingMethod atZ timingDisplay l viewer 0 OpeninventorXxt on jlabl3 jlab org File Etc Help Motion X Motion Y E a Motion Z 1 10 14 TJR G4beamline User s Guide 159 The timing process ignores everything outside of the timingVolume The timing process allows one to specify 2 out of 3 conditions maxGradient timeOffset and fixed outputs and it will determine the 3 condition if possible If it cannot find a solution G4beamline will exit with an error message For deflecting cavities the timingVolume is still aligned so the Tune particle enters one face and exits the other but the trajectory needs not be normal to the face The relationship of the particle and the RF fields is a delicate one the particle must arrive at the correct point in the RF cycle and the RF must have the correct voltage For slow particles there is an interrelationship between the phase and voltage of a cavity so changing the maxGradient may require readjusting the timing The most basic way to setup an RF cavity is to just explicitly set its timeOffset the absolute time by which th
178. hes with the error message Xlib extension GLX missing on display 0 0 or similar this means you must install the OpenGL extension g x on the system you are using to display That message may well be followed by a lengthy trace of function calls If instead it crashes with the error message error while loading shared libraries libGL so 1 cannot open shared object file No such file or directory or similar this means you must install some necessary system library on the system you are using to run g4beamline see README xt for details G4beamline X windows visualization will operate over a network but its performance will be slower than running locally even over a 100 Mbit s LAN The easiest way to do this is to use ssh with X windows forwarding enabled the X switch which is often supplied by default when the ssh client is run from a terminal window In some cases particularly on a Macintosh the Y switch may be needed instead 2 9 Obtaining Results Virtual Detectors and other NTuples While Geant4 can be used to make quite detailed models of detectors and their readouts at present G4beamline does not attempt to do so The primary purpose of G4beamline is to track particles and see where they go or don t go The most common way to obtain output is by using a command that generates an NTuple 2 9 1 Track NTuples A Track NTuple is simply a set of tuples generated for each particle that meets the requ
179. i _sigma 1775 PDGid 3116 anti_sigma 1775 0 PDGid 3216 anti_sigma 1915 PDGid 13226 anti_sigma 1915 PDGid 13116 anti_sigma 1915 0 PDGid 13216 anti_sigma 1940 PDGid 23224 anti_sigma 1940 PDGid 23114 anti_sigma 1940 0 PDGid 23214 anti_sigma 2030 PDGid 3228 anti_sigma 2030 PDGid 3118 anti_sigma 2030 0 PDGid 3218 anti _sigmat PDGid 3222 anti_sigma PDGid 3112 anti _sigma0 PDGid 3212 anti_sigma_c PDGid 4212 anti_sigma_ct t PDGid 4222 anti_sigma_c0O PDGid 4112 anti_ssl_ diquark PDGid 3303 anti_su0_ diquark PDGid 3201 anti_sul_diquark PDGid 3203 anti_t_quark PDGid 6 anti_u_quark PDGid 2 anti_ud0O_ diquark PDGid 2101 anti_udl_ diquark PDGid 2103 anti_uul_diquark PDGid 2203 anti_xi 1530 PDGid 3314 anti_xi 1530 0 PDGid 3324 anti_xi 1690 PDGid 23314 anti_xi 1690 0 PDGid 23324 anti_xi 1820 PDGid 13314 anti_xi 1820 0 PDGid 13324 anti_xi 1950 PDGid 33314 anti_xi 1950 0 PDGid 33324 anti_xi 2030 PDGid 13316 anti_xi 2030 0 PDGid 13326 anti_xi PDGid 3312 1 10 14 TJR G4beamline User s Guide 193 anti_xi0 anti_xi_ct anti_xi_c0 b1 1235 b1 1235 b1 1235 0 b _ quark c_quark chargedgeantino d_quark ddl diquark delta 1600 delta 1600 delta 1600 delta 1600 0 delta 1620 delta 1620 delta 1620 delta 1620 0 delta 1700 delta 1700 delta 1700 delta 1700 0 delta 1900 delta 1900 delta 1900 delta 1900 0 delta 1905 delta 1905 delta 190
180. i_k0O_ star 1430 0 PDGid 10311 anti_k1 1270 0 PDGid 10313 anti_k1 1400 0 PDGid 20313 anti_k2 1770 0 PDGid 10315 anti_k2_ star 1430 0 PDGid 315 anti_k2_ star 1980 0 PDGid 100315 anti_k3_star 1780 0 PDGid 317 anti_k_ star 1410 0 PDGid 100313 anti _ k _ star 1680 0 PDGid 30313 anti_k_star0 PDGid 313 anti_kaon0 PDGid 311 anti_ lambda PDGid 3122 anti_lambda 1405 PDGid 13122 anti_lambda 1520 PDGid 3124 anti_lambda 1600 PDGid 23122 anti_lambda 1670 PDGid 33122 anti_lambda 1690 PDGid 13124 anti_lambda 1800 PDGid 43122 anti_lambda 1810 PDGid 53122 anti_lambda 1820 PDGid 3126 anti_lambda 1830 PDGid 13126 anti_lambda 1890 PDGid 23124 anti_lambda 2100 PDGid 3128 anti_lambda 2110 PDGid 23126 anti_lambda_ct PDGid 4122 anti_neutron PDGid 2112 anti_nu_e PDGid 12 anti_nu_mu PDGid 14 anti_nu_tau PDGid 16 1 10 14 TJR G4beamline User s Guide 192 anti_omega PDGid 3334 anti_omega_c0O PDGid 4332 anti_proton PDGid 2212 anti_s_ quark PDGid 3 anti_sd0 diquark PDGid 3101 anti_sdl_diquark PDGid 3103 anti_sigma 1385 PDGid 3224 anti_sigma 1385 PDGid 3114 anti_sigma 1385 0 PDGid 3214 anti_sigma 1660 PDGid 13222 anti_sigma 1660 PDGid 13112 anti_sigma 1660 0 PDGid 13212 anti_sigma 1670 PDGid 13224 anti_sigma 1670 PDGid 13114 anti_sigma 1670 0 PDGid 13214 anti_sigma 1750 PDGid 23222 anti_sigma 1750 PDGid 23112 anti_sigma 1750 0 PDGid 23212 anti_sigma 1775 PDGid 3226 ant
181. ial Al color SvacuumPipeColor tubs vacuuml outerRadius 100 length 2143 material Vacuum tubs pipel innerRadius 100 outerRadius 103 length 2143 material Al color SvacuumPipeColor ut er u tubs vacuum2 outerRadius 100 length 486 material Vacuum tubs pipe2 innerRadius 100 outerRadius 103 length 486 material Al color vacuumPipeColor box vacuum3 width 300 height 200 length 1643 material Vacuum box vacuum4 width 300 height 200 length 1745 2 material Vacuum t Lay out the beamline t reference particle for manually tuning Bl and the RF reference referenceMomentum SpiMomentumRef particle pit beamZ 0 lace TargetDet z 152 parent ISISVacuum lace ISISVacuum z 0 lace ISISPipe z 0 lace vacuumWindow z 300 25 lace vacuumWindow z 399 75 lace vacuuml z 1471 5 lace pipel z 1471 5 lace QuadTypelV rename Q1 gradient Q1 z 3000 lace vacuum2 z 3700 lace pipe2 z 3700 lace QuadTypelIV rename Q02 gradient Q2 z 4400 ironColor 0 0 6 lace vacuum2 z 5100 lace pipe2 z 5100 lace QuadTypelV rename Q03 gradient Q3 z 5800 lace vacuum3 z 7078 5 OOO OOOO 1S O S OOO OS lace BendTypelI rename Bl By Bl z SBlz x 200 rotation Y30 cornerarc z 7434 2 angle 60 centerRadius 1038 5 lace vacuum4 z 8722 6 lace vacuumWindow z 9595 45 lace DecaySolenoid z 12164 7 lace vacuumWindow z 14733 95 torio tOO reference particle for manually tuning
182. ibution and learn how to build the program which will permit them to add their own C code and custom commands to G4beamline this can be much simpler than the direct use of Geant4 and its libraries The basic structure of a G4beamline simulation is to first define beamline elements magnets beam pipes windows RF cavities etc including their geometry materials fields etc and then to place them into the world usually along the beam direction As bending magnets can be modeled the beam direction can change see Centerline Coordinates below it remains simple to place elements along the nominal beam centerline It should be noted that a G4beamline simulation is closer to specifying a real beamline that it is to the abstractions and approximations used in most accelerator physics codes All descriptions and configurations are contained in a single ASCII input file which also provides values for various program parameters specification of the initial beam etc The tracking of particles through the simulated system is as accurate and realistic as the Geant4 toolkit implements The input file selects from any of the Geant4 physics lists and can set values for the various Geant4 tracking accuracy parameters This permits users to make trade offs between CPU time and simulation accuracy Similarly G4beamline permits the specification of magnetic map parameters permitting a trade off between memory usage and the CPU time to g
183. ickness to 0 scribes production of secondary particles in interactions of protons and neutrons with QGSP_BIC but with _HP modeling for neutrons o synopsis available sis available ynopsis available opsis available x RF cavity ity is the basic RF element used to construct a Acc parameter sets the phase of the tune particle the cavity and the timing offset of the cavity om that the first time that the Tune particle is the cavity Zero degrees is the rising the Ez field If timeOffset is specified it is setting it from the Tune particle and collars are always made of copper Pipe nl and win2 can be omitted by setting their Common usage is to set the collar values so by G4beamline User s Guide 76 place 1 10 14 TJR placing multiple pillboxes sequentially the collars form a beam pipe between them Note that section 4 4 of the User s Guide has a dimensioned drawing of a pillbox Named Arguments cannot be changed in place cmd Tunable maxGradient The peak gradient of the cavity MV m color The color of the cavity frequency The frequency of the cavity GHz innerLength The inside length of the cavity mm innerRadius The inside radius of the cavity mm pipeThick The thickness of the pipe wall mm wallThick The thickness of the cavity walls mm irisRadius The radius of the iris mm collarRadialThick The radial thickness of the collar mm co
184. ide 183 Appendix 4 README MacOSX txt G4beamline on Mac OS X Intel G4beamline 2 14 November 2012 TJR This version of G4beamline was built and tested on Snow Leopard Mac OS X 10 6 8 it runs on Snow Leopard Mac OS X 10 6 8 and Lion 10 7 2 G4beamline has been used in the past on Tiger 10 4 x and Leopard 10 5 x but now must be built from source to run there see BUILD txt Note PowerPC binaries are not available It is expected that installing G4beamline from source should work on older Macs running Tiger or later and at least one user has had success doing this Before installing G4beamline you probably want to install this Java installed by default as part of Mac OS X Root http root cern ch or http historoot muonsinc com You may install any version of Root because G4beamline is built with its own instance of Root and is independent of whichever Root you install If you want to use HistoRoot however you should install the version of Root from http historoot muonsinc com To install G4beamline download the installer dmg from http g4beamline muonsinc com Open it and drag the application icon into Applications requires administrator privileges if you can t do that drag it into your Home or to your Desktop You can then drag it into the Dock if desired You can run it in the usual way by double clicking on the icon single click in the dock If you want to run the programs from the comman
185. ilable in your Linux distribution but the name may be different Provides an older versin of usr lib libstdc so You probably want to install the following Root http root cern ch You may install any version of Root because G4beamline is built with its own instance of Root and is independent of whichever Root you install If you want to use HistoRoot however you should install the version of Root from http historoot muonsinc com You may want to install the following tcl should be available in your Linux distribution Required by most of the tests but g4beamline itself will run without it tcl can be installed after G4beamline if desired Many distributions install this automatically To install G4beamline download the tarball and un tar it in your HOME directory tar xzf G4beamline 2 14 Linux tgz OR tar xzf G4beamline 2 14 Linux64 tgz this will create a directory SHOME G4beamline 2 14 1 10 14 TJR G4beamline User s Guide 180 You need to put the G4beamline programs into your PATH source G4beamline VERSION bin g4bl setup sh You can put this into your HOME bash profile There is also g4bl setup csh You can create an icon on your Desktop via g4bl icon You can then copy or move it into any menu This works for both KDE and Gnome and it probably works for other window managers Once g4beamline has been put into your PATH to run G4beamline simply do cd wherever g4bl input file name value
186. ill be substituted Note this is not a general macro substitution and it only occurs in the values of command arguments In addition for all real and int valued arguments and in the param command argument values that are numerical expressions are evaluated after name substitution the standard C math functions can be used See section 4 3 on expressions and section 4 3 on parameters 1 10 14 TJR G4beamline User s Guide 128 Parameters can be defined by the param command on the command line and in the Parameters field of the GUI These last two methods permit different runs using the same input file to be different In all cases a parameter is set with the syntax name value without spaces the value can be enclosed in single or double quotes to include whitespace These examples will use the command line interface but the Parameters field of the GUI can be used in the same way The basic idea is to use a parameter rather than hard coding a specific value into the input file Usually one wants to provide a default value for the parameter so it is never undefined As an example imagine you want to compare the effects of several different target materials all with the same size The input file could look like this param unset MATERIAL Cu box Target material SMATERIAL Note the initial param unset command this provides a default value for the parameter Commands to run this simulation for several materials would be g4
187. imulated world in as simple and straightforward manner as possible so in most cases a single object you might place into a real beamline will be represented as a single beamline element in the program So for example a genericbend element represents a generic bending magnet and its field the genericbend command defines an individual magnet type including all details of both its geometry and field each placement of the magnet puts the geometrical object into the simulation and also generates the magnetic field appropriate to the magnet Other elements behave similarly In the Geant4 toolkit only simple geometrical shapes are available and complicated objects must be built up from cylinders boxes etc In G4beamline there is a rather large list of pre defined elements that are much more complicated such as an entire RF cavity including time dependent E and B fields optional windows etc or a complete absorber assembly modeled after the absorbers of the MICE experiment suitable for neutrino factory cooling channel simulations G4beamline includes simple pipes cylinders spheres boxes extruded polygons and polycones so you can build up complicated objects from them in general it is both easier and better to use the pre defined elements whenever they are suitable for your needs In cases where the pre defined elements are not sufficient it is possible to add additional elements to the program this requires C programming and the inst
188. ine app Contents Resources bin g4bl setup sh You may put this into your HOME bash_ profile There is a similar g4b setup csh The first time you run G4beamline it will launch a helper program G4bIData to download the required Geant4 data files 1 1 2 Initial Test After installing G4beamline the first thing to do is to try it on some of the example files You can double click the G4beamline icon on Windows Cygwin Linux or Mac you can also execute the command g4blgui This should bring up the G4beamline GUI window if it doesn t there is a problem with either your Java installation or your PATH Once the GUI opens click on the Browse button and navigate to the G4beamlineExamples directory and select Example g4bl on Windows go to My Documents G4beamlineExamples Clicking on the Run button should execute the Example1 simulation takes just a few seconds to simulate 1000 events Try selecting the best viewer select say 10 events run and click Run again to see the OpenInventor display of the system and a handful of events use the mouse to rotate and zoom the display If you have tcl and the bash shell available Linux Mac Windows Cygwin you can run the full test suite of G4beamline Simply cd to the install directory test and issue the command all Individual tests can be run singly if desired At present it takes about 10 minutes to run all 97 tests on a reasonably modern computer 1 1 3 Using the G4beamline C
189. ing constants can be used including common functions like sin and sqrt param a 3 0 b 2 0 name Name tubs name length Sat Sb outerRadius sqrt b 10 In the param command only argument values that are a valid numeric expression with at least one operator are converted to the value of the expression This permits such parameters to be used to perform computations for rotations and colors if desired param angle atan2 Sa Sb 180 3 14159 place Element rotation XSangle Y90 NOTE name used in a macro body the define command is substituted when the macro is defined not when the macro is expanded name in a macro body will be expanded when the macro is invoked It is possible to re define the value of a given parameter name within input file the value substituted for name is the most recent definition preceding its use Because this can be confusing to humans it is discouraged except for the do and for commands The unset argument to param will set parameters only if they are not already defined this is useful to put default values of parameters into input file while permitting them to be overridden on the command line it does not work for parameters used to control the program they are pre defined with default values 4 3 1 Program Control Parameters Several parameters are used internally by G4beamline to control its operation Name Default Description viewer none Determines the mode of the program
190. ion toward local X fixYdeflection deg change of direction toward local Y The Tune particle is repeatedly tracked through the cavity as many times as necessary to determine the timing to the timingTolerance set accuracy Independent of which method is used to determine the base timing timeOffset may be further adjusted to satisfy the requested conditions The total number of Tune particles rfdevice is typically between 5 and 200 To avoid logging them when using trace specify trace keepTune 0 For deflecting cavities the deflections are in the coordinate system used to define a cavity not the global coordinate system to avoid ambiguities when placing a cavity in the world If the final error on the requested output condition exceeds fixTolerance the default is 1 E 3 in the same units as the fixed output G4beamline will exit with an error message Though it is rarely used timelIncrement is intended for exploring small phase errors of the RF If timelncrement is set nonzero it is added to timeOffset after all other timing is complete and the Tune particle is then re tracked If the error on a fixed output condition then exceeds fixTolerance G4beamline will not report it as a an error Timing Algorithm G4beamline launches a Tune particle after each step when it is inside the rfdevice section 5 49 RfdeviceField UserSteppingAction is called That routine may make changes to the rfdevice and then push the particle back to the point
191. ipe Scl collarRadialThick 0 collarThick 0 winlThick 0 win2Thick 0 winMat Vacuum timingTolerance 0 000001 cavityMaterial Vacuum maxStep 1 timingMethod maxE timingDisplay 1 Rfdevice RF2 represents a cylindrical space of length Ldoublecell_iris2iris reduced by a tiny clearance cl to avoid overlap with a RF field described by the file RF2_1MV_wot BLfmt A G4beamline visualization of RF2 would only show the timingVolume if timingDisplay 0 and would not show anything at all with timingDisplay 0 The physical SRF cavity wall may be described as a polycone section 5 51 made of niobium polycone doublecell Z 2210 z22i11 22i12 2213 2214 2z2i15 22121 innerRadius r210 r21i1 r2i2 r2i3 r2i21 1 10 14 TJR G4beamline User s Guide 167 outerRadius r200 r201 r202 r203 Sr2021 material Nb Both the rfdevice and polycone may be placed into a macro to keep them into the correct relationship In this case both the timeOffset and phaseAcc will be determined by the timing algorithm to satisfy the condition that the exiting Tune particle have total momentum Pout param RFcolor 0 0 8 0 8 0 6 S1 2 3 doublecellAssembly lt z mm gt lt Pout MeV c gt lt V MV m gt define doublecellAssembly place doublecell z 1 color cellcolor place RF2 z 1 fixMomentum S2 maxGradient S3 rename rf2 viewer 0 OpeninventorXt on jlabl3 jlab org
192. ire hits for each trackerplane fit A track is fit to the wire hits from a previous run and the fit track is written to a TrackerFit NTuple includes true values ignore Any track is ignored See the trackermode command to control the mode of trackers The TrackerHits NTuple written in true mode contains true_x true_y true_z true Px true Py true Pz true t true PDGid true EventID true TrackID true _ParentID true Weight plus 1 hit and 1 time per trackerplane the first 12 are the same as a BLTrackFile The TrackerFit Ntuple written in fit mode contains X Y Z Px Py Pz t PDGid EventID TrackID ParentID Weight ChisqPerDF nDF nHit niter true_x true y truei true Py true _ Pz true t the first 12 are from the fit and are the same as a BLTrackFile The parameters of the fit are x y dxdz dydz Ptot time Zy You must ensure that there are at least as many data points as free parameters scaleT 0 fixes time scalePtot 0 fixes Ptot Each trackerplane with nonzero wireSpacing provides a data point trackerplane with nonzero sigmaT provides a data point each trackerplanes that measure both provide two data points You must have enough trackerplanes to meet this requirement and must minHits large enough to meet it The TrackerFit NTuple has a field nDF that gives the number of degrees of freedom for the fit which is defi
193. ireframe which will draw in the wireframe mode rather than as solid surfaces This permits you to look inside objects and is considerably faster drawing The Etc menu has several useful items Set Solid Set the G4 mode to Solid default Set G4 reduced wire frame Set the G4 mode to wireframe real edges only Set G4 full wire frame Set the G4 mode to wireframe 1 10 14 TJR G4beamline User s Guide 22 including triangles to fill surfaces Visible mothers invisible daughters Daughter volumes are invisible default Visible mothers visible daughters Make all objects visible The key to understanding how objects are displayed is to know that Geant4 has a solid wireframe choice and OpenInventor has a solid wireframe choice and they are different G4 mode OI mode Description Etc menu Right click menu Solid Solid as is Draw solid surfaces Solid Wireframe Draw wireframes with triangles filling visible surfaces Reduced Either Draw reduced wireframes showing only real edges Wireframe Full Either Draw wireframes with triangles filling visible surfaces Wireframe For instance in G4 reduced wireframe mode a sphere is invisible as it has no real edges in G4 full wireframe mode it has triangles filling its visible surface in such a way you can tell it is a sphere In reduced wireframe mode a cylinder is drawn as two circles Note that by default
194. irement for generation the columns are fields with names and the rows are the individual track hits The list of fields is given below 1 10 14 TJR G4beamline User s Guide 24 The following commands generate an NTuple for tracks e A virtualdetector is an idealized perfect detector that detects every track that hits it and measures all of the track properties with the resolution of a 32 bit float including position 3 momentum particle type event etc It is virtual because any material including Vacuum can be used and by default it uses the material of its parent so it doesn t affect the tracking of particles Multiple tracks from a given event that hit the virtualdetector will be stored as separate rows in the NTuple with the same EventID as will multiple hits from a single track with the same EventID and TrackID The measurements for all such tracks are output to a file as an NTuple e A detector is similar to a virtualdetector except it must have a realistic material default is Scintillator It output the track information as above plus the energy deposited and the visible energy deposited modified by the Birks effect e A zntuple is similar to a virtualdetector except that no physical volume is used whenever a track reaches the specified Z position centerline coordinates it is sampled in the same manner as a virtualdetector All zntuple s are named Z100 with the number being its Z position rounde
195. is is a difficult problem as Geant4 tracks in space not time and for a stopping particle the equations of motion become singular A number of Geant4 processes have auxiliary commands that can vary their operation See the Geant4 documentation for details in most cases these are not important but when they are the g4ui when 0 command can be used to execute the necessary Geant4 commands Geant4 tracking requires that the simulated world s geometry be a rigorous hierarchical structure violations of this requirement can cause gross tracking errors By default G4beamline performs a geometry test to check for invalid volume overlaps and conformance to this requirement failures generate a warning but permit the simulation to proceed The geometry command controls its parameters Section 8 2 discusses when these rules can be violated without affecting the simulation results The pseudo random number generator is normally seeded with the event number immediately before starting to process an event The generator used has excellent properties when seeded with integers from 0 thru 900 000 000 This behavior can be changed via the randomseed command As in real beamlines shielding is required in realistic simulations See section 7 9 Individual physics processes can be disabled via the disable and doStochastics arguments to the physics command A list of the physics processes used in the current physics list is available from the list command 1 10 1
196. isto_event txt file You can then check the HistoRootEvents checkbox in the GUI or put an eventcuts command into your input file Running with a viewer will then permit you to visualize just the crazy events seeing them will often let you figure out what s wrong Note that G4beamline simulations are quite realistic This means that pions and muons will decay particles will interact in material objects and tracks will propagate wherever they can go even if you don t expect it Decay neutrinos can look crazy if you re not expecting them so cut on PDGid in the plots or eliminate them at the source with a trackcuts in your input file You may be surprised at the delta rays low energy electrons produced in vacuum windows and other materials eliminate them with a trackcuts command with kineticEnergyCut 1 or higher or perhaps kil e Tracks can occasionally go in the most amazing places and you need to install shielding just as in a real accelerator use the radius Cut as described above or add a box or tubs with kill 1 and place it appropriately when complete you can use color invisible to avoid cluttering your visualizations It is often appropriate to surround the beam line with beam pipes having kil this avoids spending CPU time on unwanted tracks and prevents them from taking shortcuts and re appearing as crazy events in plots add kill 1 to quads and bends etc In my experience the most common errors i
197. kfilter that filters tracks via user code 1 10 14 TJR Named Arguments radius The radius of the circular element mm innerRadius The inner radius of the circular element 0 mm solid height The height of the rectangular element mm width The width of the rectangular element mm length The length of the element mm maxStep The maximum stepsize in the element mm material The material of the element color The color of the element invisible filterName Name of the UserTrackFilter filter Synonym for filterName G4beamline User s Guide 97 init Initializa virtualdetector Construct a VirtualDe A VirtualDetector genera tion string passed to user setup tector that generates an NTuple tes an NTuple of any track when it enters 1 10 14 TJR the physical volume of the VirtualDetector multiple place commands usually with a rename det distinguish the different placements specified it uses the material of the enclosing element placement creates an individual NTuple For a circular VirtualDetector give radius and width length is usually left at 1 mn correspond to the length of a physical detector default uses centerline coordinates The NTuple of the It may be placed via argument to If material is not Every for a rectangular one give height but can be set The NTuple by CO virtualdetector can be included in an ntuple command by including
198. l 6 11 Movie in Movie in input file to g4blmovie command for SampleMovie g4bl with movie command outputs a Flash movie setup outputFile SampleMovie swf tMin 0 001 tMax 18 duration 10 t red mu blue others gray neutrtinos particle 11 FF0000 13 0000FF 0 808080 plot filename g4beamline root xMin 800 xMax 800 yMin 800 yMax 800 x x y y plot xMin 200 xMax 200 yMin 200 yMax 50 x z y Pz row plot xMin 800 xMax 800 yMin 50 yMax 50 x x y Px plot xMin 800 xMax 800 yMin 50 yMax 50 x y y Py row height 0 2 sideview xMin 100 xMax 5000 yMin 2000 yMax 2000 markerSize 2 0 row height 0 1 time textHeight 12 space title Example6 textHeight 12 position textHeight 12 1 10 14 TJR G4beamline User s Guide 116 6 12triplet sh tune a quad triplet for point to point focus This shell script requires the bash shell and the following programs e Gbeamline http g4beamline muonsinc com e gminuit http muonsinc com ComputerPrograms gminuit e gnuplot available from your Linux distribution or http sourceforge net e tclsh and wish available from your Linux distribution The gminuit program is configured to have the following parameters P dP sigmaXp sigmaYp QF QD The first four determine the initial beam which emanates from a point and the last two determine the gradients of the three quads The Chisquared to be minimized is sigmaX 2 sigmaY 2 evaluated at Z 6000 so
199. l Thick collarThick A l irisRadius gt lt win2Thick i winMat eae W oni aai l 1 WinlouterRadius gt lt win Thick _ VENETO Beam axis 4 5 Absorber geometry and Dimensions The absorber is cylindrically symmetric around the beam axis The beampipe s radii come from the flange specifications in the files that define the profiles of the absWindow and the safetyWindow the beampipe s length is extended to the same length as the safetyWindow s on the beam axis The safetyDistance is between the inner faces of the two windows on the beam axis If safetyWindow is omitted all references to it are changed to absWindow and there are no volumes of safetyMaterial safety Window abs Window innerR outerR innerR outerR safetyDistance ay A Beam axis absMaterial safetyMaterial Safety Absorber Beampipe Window Window windowMaterial 1 10 14 TJR G4beamline User s Guide 41 4 6 Cornerarc geometry The cornerarc command approximates an arc in the centerline coordinates by using three corner s arranged so the path length is the same as that of the arc The figure is for angle 90 degrees The z value is that of Corner 1 The path length is determined by centerRadius and angle Corner 3 Corner 1 centerRadius Centerline Coordinates 4 7 genericquad Aperture The genericquad command can have two types of aperture a circle and a rounded The former is specified by setting
200. l X Y Z coordinate axes of the enclosing group centerline or global coordinate axes for the World group groups can be rotated when placed and are rotated as a rigid unit including children If parent name is present then the name must be an element that accepts children and it is used as the enclosing group in this case the size of the group is implied by the size of the parent element and z must be given defaults to 0 Note that a given element cannot be the parent of any other element once it has been placed so you must place children into their parent before placing their parent If the special element OFFSET is given x y and z specify offsets for every following place command into the current group incl World that gives a z position Named Arguments Z Z position of element s center relative to the center of the enclosing group mm x X position of element s center default 0 mm y Y position of element s center default 0 mm parent Parent element name must accept children rename Name to use for this placement will be substituted by the number of placements If the value begins with it is replaced with the parent s name copies Number of copies placed sequentially along z front Nonzero to specify z for the front not the center rotation Rotation of this object coordinates Coordinates global or centerline default
201. l probably max out around 10 20 ranks because the serial operations in rank 0 will saturate For a simulation that runs 13 ev sec on a Hopper worker node rank 0 saturates around 800 workers From the parallelization plots in section 8 5 4 below it s clear that on Hopper rank 0 saturates around 8 000 events per second There are several design and code changes that could be done to mitigate the rank 0 bottleneck but for now this is not considered serious enough to warrant development Note that a larger number of messages per event will reduce the number of workers that can be used effectively because the serial I O in rank 0 will dominate So for high performance avoid printf steppingVerbose 1 trace and a large number of NTuples There can be rather large overheads in starting each MPI process on Hopper 1600 ranks can take several minutes to start up from rank 0 starting to the last worker processing its first event Startup is loosely but not strictly in rank order The best way to estimate how many workers to use is to plot the performance events per second as a function of the number of workers When rank 0 becomes saturated the events per second will likewise saturate Usually a few minutes will suffice for each point and you can use the wallClockLimit parameter to terminate the jobs Be sure it is large enough for all workers to start up if they don t all start up the symptom is a droop in the Events sec vs nWorkers plot
202. lace SciFi rename Tracker2d z 595 5 place SciFi rename Tracker2e z 1045 5 place TrackerWindow z 1245 0 endgroup Het The MICE Absorbers Ht APPROXIMATION I used an old spreadsheet to compute window profiles absorber Abs absWindow Windows abs300 safetyWindow Windows safe320 insideLength 350 absMaterial SabsMaterial windowMaterial Al safetyDistance 133 color 0 1 0 tubs AFCPipe innerRadius 160 outerRadius 263 length 850 material Al color SvacuumPipeColor group Absorber radius 0 material Vacuum length 850 place Abs rename z 0 place AFCPipe z 0 endgroup Hitt The MICE RF Linacs Hitt APPROXIMATION the drawings in the Mar28 TRD gave no dimensions so these Hitt are Study2 RF cavities APPROXIMATION the RF windows are flat 0 38mm thick 1 10 14 TJR G4beamline User s Guide 111 pillbox Pbox maxGradient 16 frequency 0 20125 innerLength 430 pipeThick 3 wallThick 3 irisRadius 210 collarRadialThick 25 collarThick 12 5 winlThick 0 38 winlOuterRadius 140 win2Thick 0 38 winMat Be phaseAcc 40 skinDepth 0 1 timingTolerance 0 001 tuneEnd RF2C1 goalFactor 1 0 initialStep 0 5 tuneTolerance 0 001 for empty absorber and no RF pillbox Pbox maxGradient 0 frequency 0 innerLength 430 pipeThick 3 wallThick 3 irisRadius 210 collarRadialThick 25 collarThick 12 5 winlThick 0 38 winlOuterRadius 140 win2Thick 0 38 winMat Be skinDepth 0 1 innerRadius 608 5 tubs RFPipe
203. lar VirtualDetector mm width The width of the rectangular VirtualDetector mm length The length of the VirtualDetector mm maxStep The maximum stepsize in the element mm G4beamline User s Guide 98 zntuple 1 10 14 TJR material The material of the VirtualDetector color The color of the VirtualDetector invisible noSingles Set to 1 to omit the NTuple for singles format NTuple format see above for list filename filename uses name to determine filename file alias for filename require Expression which must be nonzero to include the track default 1 referenceParticle Set to 1 to include the Reference Particle coordinates Coordinates global centerline or reference default c kill Set to 1 kill all tracks after entering them into NTuple s Generate an NTuple for each of a list of Z positions Generates an NTuple like a virtualdetector but without a physical volume Tracks are forced to take steps within 2mm surrounding each desired z position and they are interpolated to the desired z position Each z position generates a separat NTuple named 2123 etc z accepts a list of z positions and zloop can generate a set of equally spaced z positions both can be used Each value in z and zloop can be an expression using double constants and the usual C operators and functions The standard NTuple fields are x Y Z mm Px Py Pz MeV c t n
204. lar to Mac OS X Hopper runs a supercomputer version of Linux G4beamline is written such that if you just run it by itself via the g4b script via the g4b gui program or via an icon it runs without MPI as a single local process But if it is run via the g4b mpi script then it runs the specified number of instances and operates in MPI mode via either mpirun or aprun depending on which is available In MPI terminology each instance of the program is called a rank the ranks are enumerated by a non negative integer unique to each instance of the program assigned by the MPI system sequentially from 0 For G4beamline rank number 0 is the master controlling instance and all other ranks are worker instances nodes The usual command is g4bimpi 5 input file parameters 1 10 14 TJR G4beamline User s Guide 152 This command acts very nearly like a single G4beamline program simulating input file except it uses 5 processes to speed up the computation The basic operation is 1 Setup the environment as in g4b This includes locating the shared objects and the Geant4Data 2 Start 5 instances of the g4beamline program using mpirun s internal mechanism to start them 3 Each instance of g4beamline determines that it was run via mpirun and gets its rank number from the MPI library 4 The rank 0 instance does the following a Reads input file constructs the geometry the physics list etc b Creates an output file for each
205. le shell script to run the jobs in the background see previous tip On a 4 core system it is usually best to run four jobs in the background do a wait run four jobs in the background etc In the bash shell wait no arguments waits until all background jobs have completed so this does a reasonably good job of keeping four jobs running but does not overload the system with too many simultaneous jobs 7 24Visually Scanning Events via the Command Line The simplest way to scan events visually is to use the g4b gui program but it can be done manually via the command line The OpenInventor driver OIX has the ability to exit the viewer and return to the 1 10 14 TJR G4beamline User s Guide 134 Geant4 command input File Escape This can be used to quickly scan events visually To do this first create a text file called beamon txt containing a large number of identical lines run beamOn 1 run beamOn 1 run beamOn 1 Many more identical lines Then invoke g4beamline like this g4bl input file viewer best lt beamon txt Once the viewer appears it will display the first event To see the next event select the File Escape menu item This will suspend the OpenInventor viewer and the Geant4 input routine will read the next line of beamon txt that causes it to track one event and refresh the viewer with it Just keep selecting File Escape to sequence through events one at a time This is essentially what the g4blgui program does
206. length 5138 radius 0 material Vacuum place DecayShield z 2568 place DecayEnd z 2534 place DecayS z 0 place SolenoidBody z 0 place DecayEnd z 2534 endgroup Proton Absorber material H Z 1 A 1 00794 density 0 0838 material C Z 6 A 12 011 density 2 265 material polyethylene density 0 93 C 0 856 H 0 144 50mm cos 15 deg 48 29 box ProtonAbsorber width 400 height 400 length 50 material polyethylene color 1 0 1 Type QC Quads includes mirror plates genericquad QuadTypeQc fieldLength 660 poleTipRadius 171 5 coilRadius 236 kill 1 Diffuser The beamline GUESS 0 5mm 1 10 14 TJR coilHalfwidth 57 ironRadius 700 ironLength 1046 ironColor 0 6 0 tubs Diffuser outerRadius 200 material Pb length SDiffuserThickness color 1 0 1 virtualdetector DiffuserDet radius 200 length 1 Collimator place twice on beam left and right box Collimator width 600 height 500 length 150 material Fe color 8 8 8 kill 1 vacuum components GUESS vacuum windows are 0 5mm Al flat Al flat isolation windows at each end of DecaySolenoid NOTE vacuum3 and vacuum4 intersect Bl this is OK as all are Vacuum G4beamline User s Guide 108 tubs ISISVacuum outerRadius 100 length 600 material Vacuum tubs vacuumWindow outerRadius 120 length 0 5 material Al color vacuumPipeColor tubs ISISPipe innerRadius 100 outerRadius 103 length 600 mater
207. lesource command can be used but the GPS permits multiple sources to be combined NOTE the Geant4 General Particle Source inherently uses global coordinates so this is most useful at the beginning of a beamline when global centerline Note also that it is very easy to generate a beam headed in the z direction this command will rotate to the z direction gps ang rotl 1 0 0 To use this see the User Manual for the GPS at http reat space qinetiq com gps Named Arguments nEvents Number of events to process default 1 set to lastEvent firstEvent l if both are set firstEvent First event to process default is the next sequential eventID 1 if none lastEvent Last highest event to process secondaryTrackID The next TrackID for secondaries 1001 Defines the physics processes and controls them Exactly one physics command must be present This command implements the geant4 physics lists of physics processes The command is physics QGSP for the QGSP list and similarly for the other lists With no argument it prints the available physics lists default will select a standard list currently FTFP BERT Note that stochastic processes are always disabled while tracking the tune and reference particles The only non stochastic processes are Transportation and ionization energy loss with fluctuations disabled For muon beam studies you may want to disable the Decay
208. lf the desired angle In X and Z centerline coordinates correspond to what a surveyor might draw on the floor a piecewise linear centerline along which the various beamline elements will be placed Note that just like a real beamline in G4beamline the fields of bending magnets must be adjusted tuned so that the desired reference particle will travel along the centerline of the beamline In general the fringe fields of bending magnets will require them to be offset slightly from their nominal position relative to a corner of the centerline See section 7 18 for a description of how to place and tune bending magnets If your input file has no start corner or cornerarc commands then the centerline coordinates will be the same as the global coordinates everywhere Note that in the input file each start corner or cornerarc command affects the centerline coordinates immediately This means that all elements to be placed between a given pair of corners must be put into the input file between those corner commands If you attempt to place an object using a Z position in front of a previous corner or cornerarc or behind a following one it will almost surely not do what you intend Because of this it is quite difficult to place any element inside a bending magnet using centerline or global coordinates the best way to do that is to use the genericbend object as the parent for the placement Because centerline coordinates can only apply
209. lines until maxPoints is reached or B lt minField initial plane implements a field map E and or B from a fi le not stopping at the a Reads an input file in BLFieldMap format to define E and or B fields optionally with tim d th Users Guide for pendence S a description of the BLFieldMap format Note that front 1 can NOT be used to place this field Named Arguments cannot be changed in place cmd Tunable filename Filename for the Field Map file Synonym for filename current Current of the B field gradient Gradient of the E field timeOffset Time offset ns Generates an NTuple from B and Intended primarily for debugging plot fields as a function of position and time NTuple plotting tools Outputs x y z t Bx By Bz NTuple Units are mm ns Tesla E fields at specified points This command makes it easy to using existing Ex Ey Ez into an and MegaVolts meter Runs after the reference particle is tracked Only global coordinates are used The single positional argument arguments x y z t are of two values x Xmin Xmax dX or x X1 is obvious loops single value is the name of the NTuple Named forms specifying coordinate X2 X3 which generate the OK Expressions can be used Omitted coordinates are held fixed at 0 0 Named Arguments category The cat
210. llarThick The thickness of the collar along z mm winlThick The thickness of the central portion of the windows zero for no window mm winlOuterRadius The radius of the central portion of the windows mm win2Thick The thickness of the outer portion of the windows zero for no window mm winMat The material of the windows phaseAcc The reference phase of the cavity degrees skinDepth The skin depth mm timingTolerance Tolerance for timing tuning ns maxStep The maximum stepsize in the element mm cavityMaterial Material of cavity volume Vacuum timeOffset Time offset for cavity default tuned by tune particle ns timeIncrement Increment to timeOffset applied AFTER tuning ns fieldMapFile Filename for BLFieldMap pillbox if null kill Set nonzero to kill tracks that hit the pipe walls or collars 0 places an element into the current group or world Every element can be placed multiple times into the beamline For most elements the geometrical centerpoint is placed for polycone the local x y z 0 point is placed If front is nonzero then the front of the element is placed and any rotation is applied at the front If z is specified then th lement is placed at that z position relative to the center of the enclosing group If z is not specified then th lement is placed immediately downstream higher z of the previous element in the group or a
211. long printout Those that are issued by a routine beginning with G4 came from Geant4 code while those issued by a routine beginning with BL came from G4beamline code those that are 1 10 14 TJR G4beamline User s Guide 126 issued by a command names are also from G4beamline code It is important to distinguish these two cases as how you obtain help on them may differ The severity of the message is a strong indicator of whether it can be ignored or indicates a serious problem Note that a Warning issued by many events probably means the simulation cannot be trusted Warnings on a tiny fraction of the events can probably be safely ignored unless they are related to specific rare events of interest Even Errors that abort the track or event might well be ignorable if they occur only rarely Note that G4beamline suppresses many similar exception printouts so look at the Exception Summary at the end of the output to see how many actually occurred Errors issued by G4beamline code can be discussed in our user s forum http www muonsinc com tiki view_forum php forumId 1 You can also send email to mailto inquiries muonsinc com or to Tom Roberts the primary author of G4beamline mailto tjrob muonsinc com Errors issued by Geant4 code can be discussed in the Geant4 forums linked to the Geant4 home page http geant4 cern ch You can also discuss them as in the previous paragraph choose one method not both S
212. lue of scale is guessed As each line is placed all grid points within scale B of its location in the circle are excluded The next point is placed at the un excluded grid point that is closest to the center of the circle and nearby grid points are excluded This continues until all grid points have been excluded If the total number of field lines placed is within a factor of 2 of the desired number this set is accepted and the field lines are drawn If the number placed is too small scale is reduced and the procedure is repeated if the number placed is too large scale is increased and the procedure is repeated At most 10 iterations are permitted This implies that asking for fewer than 5 lines or more than 1 000 lines is likely to be ineffective This algorithm gives a good distribution of field lines for solenoids and other simple fields 1 10 14 TJR G4beamline User s Guide 141 Once the lines are placed within the circle for each one the B field is traced in both directions there are three criteria for stopping drawing a given half line a The line intersects the plane of the circle 1 e it has come back to the plane but outside the magnet b The value of B falls below minField c The field line leaves the simulated world There are additional arguments to the fieldlines command that control the drawing Remember the field lines are drawn in 3 dimensions so they won t look like the pictures in a textbook This is a featur
213. lways emit an extra gamma or more than one which is called a radiative decay It is not generally realized how frequently this occurs or how important it can be in some cases generally backgrounds For a multi TeV muon facility the radiative muon decays produce an intense gamma beam parallel to the muon beam for gamma energies above GeV it can be comparable in number to the muon decays with gamma energies up to hundreds of GeV this is a background above and beyond that of the decay electrons and cannot be ignored The Geant4 Decay process does not include radiative decays The MuonDecayWithSpin process does include them and can be enabled on the physics command by setting spinTracking 1 works even with unpolarized muons gt The PDG booklet lists the branching ratio for radiative muon decay as 1 4 with a note stating this is for gammas with energies above 10 MeV For a TeV scale muon beam gammas of much lower energy get boosted to multi GeV energies the branching ratio for them is about 25 when using MuonDecayWithSpin 1 10 14 TJR G4beamline User s Guide 34 3 9 Miscellaneous There is a bug in Geant4 tracking that makes gross errors when tracking a particle that stops and turns around e g it is traveling exactly opposite to an E field sufficient to stop it This has been reported as Geant4 bug 1021 and the command bug 02 implements a work around that resolves the issue with an accuracy of a few microns Th
214. ly or via scripts 2 Via the Message Passing Interface MPI 7 22 1 Manually or via Scripts G4beamline is a realistic simulation program and runs considerably slower than many accelerator simulation programs While simple simulations can run as fast as 1000 events per second a moderately complicated system might run 100 events per second and complex simulations can run less than 1 event per second With the advent of Linux clusters and multi core CPUs it is now quite common to be able to run multiple jobs in parallel The key to doing that in G4beamline is that it always seeds the pseudo random number generator with the event number just before starting to process the event The PRNG used comes from CLHEP 2 and has excellent properties for event numbers from 0 to 900 000 000 These basic capabilities are needed to run multiple jobs in parallel 1 The ability to submit multiple jobs This is system dependent On a multi core or multi CPU system you can simply use multiple terminal windows or multiple GUI windows to run multiple jobs simultaneously Be sure to keep the jobs separate including output files On Linux Mac OS and Windows Cygwin you can use a single terminal window to run several jobs simultaneously in the background g4bl input file first 1000000 last 1 199999 gt 1000000 out amp g4bl input file first 1200000 last 1299999 gt 1200000 out amp g4bl input file first 1300000 last 1399999 gt 1300000 out amp On a Linu
215. ly simulate beamlines and other systems It is flexible enough to simulate complex beamlines like the MICE muon beam the Neutrino Factory Study 2 SFOFO muon cooling channel complex helical cooling channels and many others Because of its simple and straightforward method of specifying the system to be simulated it is also well suited for quickly answering questions about particle interactions and tracking e g On average how much energy does a 150 MeV proton lose in a 1 mm Al window How large does the multiple scattered beam grow 20 meters downstream of the window As a Cosmic Ray muon beam is included the notion of beamline can be rather more general than usual The primary advantage of using G4beamline is that its description of the simulation is commensurate with the complexity of the system being simulated instead of being a significantly more complicated C program Most users need not face the challenges of learning C programming and the details of the Geant4 toolkit to use G4beamline there is no need to a know C b learn the many aspects of the Geant4 toolkit API c face the non trivial challenges of installing the Geant4 toolkit and all its required libraries and d learn how to solve any problems that arise while linking a complicated and rather large program All of that is done during the production of the G4beamline distribution Users with special needs can download and install the source distr
216. ly your desktop or laptop must have the 3 D display capabilities of OpenGL installed as must the X client where G4beamline is running When you startup the OpenInventor viewer the window looks like this MICE_StageVI g4bl 1 10 14 TJR G4beamline User s Guide 21 bd Viewer 0 Openinventorxt eiim x File Etc Help Rotx Roty The Rotx and Roty wheels rotate the image relative to the viewer and the Dolly wheel moves in and out with a corresponding change of scale The buttons along the right edge do the following Arrow Select pick mode and cursor Hand Select move mode and cursor default Help not implemented House Restore display to Home position House with arrow Set Home position to be the current display Eye Zoom so everything is visible Gunsight Not implemented Perspective box outline Select isometric or projected display When the Hand cursor is active the mouse behaves like this Left Button Click and drag to rotate the display It acts as if there were an invisible sphere surrounding the image and the mouse movements rotate that sphere in any direction This is quite different from the Rotx and Roty wheels and takes some getting used to Middle Button Click and drag to pan the display this moves the visible objects around without rotation Right Button Brings up a menu with various functions Draw Styles and other items The most useful is DrawStyles StillDrawStyle W
217. me is split in two to ensure the track takes a step ending in the center of the cavity If the phase is correct within tolerance nothing further is done and the Tune particle continues being tracked If the phase is incorrect the timeOffset value is adjusted via a simple linear solver the current Tune particle is killed and a new Tune particle is generated from the saved values This usually converges in one iteration If timeIncrement is nonzero it is added to timeOffset after all tuning is complete The Tune particle is not re tracked so large values will completely confuse the reference particle timeIncrement is intended for exploring small phase errors of the RF See also section 2 11 Tuning the Beamline 7 21 Tuning the maxGradient of RF Cavities pillbox When RF cavities are used it is generally necessary to carefully tune their maxGradient so the output beam has the desired energy or momentum The operators of the machine arrange for this either manually or via an automated feedback system In G4beamline this requires the tune command and is done while tracking the Tune particle usually in parallel with setting their phases see previous section The tune command defines a tune variable and will arrange to save the Tune particle at one Z position z0 track the Tune particle to a second Z position z1 and then evaluate an expression using track fields It then varies its tune variable in an attempt to make the expressi
218. ment The Cygwin environment is not needed to run G4beamline itself it is needed just for building the program and running the tests RUNNING THE PROGRAM GUI Simply double click the G4beamline icon On Windows it is placed on your desktop and in the Start G4beamline menu On Mac OS X it is placed where you dragged copied it when you installed it On Linux the g4bl icon script will create one on your desktop To run the GUI program via the command line source G4beamline VERSION bin g4bl setup sh optionally cd where your input file is located g4blgui input file This requires Java and a display X Windows on Linux and Mac OS X nothing special on Windows Its opening screen decribes how to use it To run the examples simply push the Browse button navigate to the install directory examples and select Examplel g4bl or other g4bl file Then select the desired viewer if any and push the Run button On Windows a copy of G4beamline Examples is put into My Documents Windows Xp or Documents Windows Vista On Mac there is a copy of G4beamlineExamples on the install dmg RUNNING THE PROGRAM COMMAND LINE For command line use Linux Mac OS X and Windows with Cygwin you must add G4beamline s bin directory to your PATH source G4beamline VERSION bin g4bl setup sh You can put this into HOME bash profile There is also g4bl setup csh Then cd to whatever directory you plan to use for developing your si
219. mm steppingFormat Format for printing steps steppingVerbose Set nonzero to print each step viewer Visualization driver selected default none wallClockLimit Limit on wall clock time in seconds 1 is infinite worldMaterial Material of the World volume zTolerance Tolerance for Z steps mm steppingFormat is a space or comma separated list of items EXT toggle extended precision 3 more digits TAG print a gt useful to grep output N step number NSTEP Synonym of N GLOBAL X Y Z T in global coords XYZT Synonym of GLOBAL CL X Y Z dxdz dydz in CL coords CLX extended precision CL KE kinetic energy STEP step length STEPLEN Synonym of STEP VOL volume name VOLNAME Synonym of VOL PROCESS process name B magnetic field E electric field P 3 momentum MAT material name ID event ID track ID parent ID PART particle name SEG centerline coord segment number WT weight POLAR polarization NL lt newline gt NEWLINE Synonym of NL n Synonym of NL 1 10 14 TJR G4beamline User s Guide 45 5 G4beamline Commands Alphabetical absorber construct an absorber The absorber has two windows with beampipe and an absorber material Optionally it has an additional two safety windows with beampipe The WindowShape s are read from a file and they determine the thickness and length of the beampipe s For geometry testing acts like a cylinder enclosing the windows For placing children acts like a cylinder inside the central absorb
220. mmands and code the HistoRoot program makes it unnecessary to know Root and C and guides you through most common tasks HistoRoot can read multiple Root files 7F ile and can generate plots from the TNtuple s in them It can also read ASCII files in either csv or column format and convert them to TNtuple s for plotting see the Help for details on the ASCII file format a structured comment can associate names to the columns HistoRoot was inspired by the HistoScope program 3 though its user interface is completely different Having a simple GUI to generate plots and histograms is quite useful and having sliders that interactively impose cuts on the histogram is a great convenience 1 2 License and Distribution This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 2 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details http www gnu org copyleft gpl html This application includes software developed by others see the Acknowledgements in section 10 below 1 10 14 TJR G4beamline User s Guide 10 2 Basic Concepts Any physical component of the simulation is called a be
221. mulation s and execute g4bl After a few seconds it should type with obvious variations G4BL_DIR Users g4b1 G4beamline G4LEDATA Users g4b1 G4beamline data G4EMLOW6 2 G4LEVELGAMMADATA Users g4b1 G4beamline data PhotonEvaporation2 0 DYLD LIBRARY PATH Users g4bl1 G4beamline LibraryBinaries Darwin gtt G4beamline Process ID 68927 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk g4beamline version 2 10 17 Dec 2011 14 14 Copyright Tom Roberts Muons Inc 1 10 14 TJR G4beamline User s Guide 178 License Gnu Public License www http g4beamline muonsinc com kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Geant4 version Name geant4 09 04 patch 03 9 December 2011 Copyright Geant4 Collaboration Reference NIM A 506 2003 250 303 WWW http cern ch geant4 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk geometry nPoints 100 printGeometry 0 visual 0 tolerance 0 002 cmd The program is now ready for input Type help to get a short list of the input file commands help beam to get help on the beam comand or help for a detailed description of all commands This is a useful way to get help on commands when editing your input file s Type C to exit back to a shell prompt EXAMPLE 1 The first example input file is Examplel g4bl It is a simple file to track muons through 1l1 meter drift spaces into 4 detectors To visualize its geometry using OpenInventor execu
222. n The Coin 3D graphics library http coin3d org 10 Gnuplot http Awww gnuplot info 11 OpenMPI http openmpi org 12 NERSC http nersc gov the supercomputer itself is http hopper nersc gov 13 Cosy Infinity http www bt pa msu edu index_cosy htm 1 10 14 TJR G4beamline User s Guide 201
223. n reference hits an aperture and is killed If this does not happen naturally you could use a particlefilter to kill the pion reference at an appropriate place Tuning will get confused if multiple reference particles enter the tune region 7 27 Fitting to Plots and Histograms in HistoRoot A major advantage of using HistoRoot is the fact that it is based on Root 5 and has all of the Root features at its disposal This includes the ability to fit functions to plots and histograms The Root user interface is quirky but quite functional To fit a function to a histogram first generate the plot containing the histogram Right click on the histogram itself one of its bins not the canvas and not any axis or other object the cursor changes from cross to arrow when clicking will select the histogram that s what you want and then select FitPanel The FitPanel lets you select from among a number of pre defined functions and a user defined function Name Description gaus A Gaussian distribution gausn A normalized Gaussian distribution expo An exponential distribution landau A Landau distribution landaun A normalized Landau distribution pol0 pol9 A polynomial of order 0 through 9 user A user defined function use 0 1 for the parameters to be fitted and make it a function of the variable x or x and y For instance here is a 1 d Gaussian 0 exp 0 5 x 1 x 1 2 2
224. n G4beamline simulations and interpreting results are 1 Failure to cut on PDGid in plots and histograms and thus confusing other particles for the desired ones 1 10 14 TJR G4beamline User s Guide 123 2 Failure to put shielding in appropriate places and thus having particles go in unexpected places causing crazy events in plots and other confusion Mistakes in the input file that cause invalid overlaps of objects Mistakes in the input file that unintentionally omit objects or put them in the wrong place 5 Inappropriate values of tracking parameters see section 3 that cause Geant4 to optimize tracking in an unsuitable or insufficiently accurate manner aS 7 11 Geant4 Commands Geant4 has an internal command processor with a large number of commands For the most part G4beamline users don t need to use these commands as G4beamline controls all aspects of the simulation Nevertheless there are situations for which a user might want to issue a Geant4 command There are two rather different ways to do this 1 Simply put the Geant4 command into the input file putting its initial in column 1 Such commands are issued when they are read that happens before the system is constructed and for many commands that is too early 2 Use the g4ui command The when argument controls when the command is issued and all values are after the system is constructed The Geant4 command interpreter is quirky but there is a
225. n element is only valid inside its aperture plus perhaps a short distance away for a fringe field This is so for genericbend and genericquad but solenoid and fieldmap have fields throughout space which are truncated according to the tolerance specified or the limits of the map In Geant4 programs computing the field is usually the dominant CPU time used during tracking In order to minimize this CPU usage G4beamline optimizes the computation of the field by using a global bounding box around the field of each element The World volume is divided into rectangular voxels and during initialization each voxel is given a list of all fields whose bounding boxes intersect the voxel The voxel size is given by the parameter fie dVoxels which defaults to 200 200 200 200 mm on each side To compute the field at a given point the program computes the voxel containing the point and then sums the fields from the voxel s list Note this is quite different from Geant4 where geometry and fields are strictly separate and voxels are not used in the field computation 2 8 Visualization The ability to easily visualize the system being simulated is an important part of G4beamline Without visually examining the system in detail it is easy to make simple mistakes that completely invalidate the results of the simulation Users are strongly urged to use visualization frequently In order to be visible a given beamline element must be given a colo
226. n the ntuple command neither of these can be avoided without massive changes that adversely affect users TrackID is intended to identify a track within an event For internally generated beams the primary track has TrackID 1 but for beams read from external files the assignment of TrackID to tracks is contained in the file this means that multiple tracks with identical EventID s can have the same TrackID s Moreover secondary tracks can be generated during the simulation of an event and the TrackID s for them can potentially conflict with TrackID s read from a file By default secondary TrackID s are assigned starting at 1001 see secondaryTrackID of the beam command If a beam track from an external file has a TrackID gt secondaryTrackID a warning will be printed For beam files containing TrackID s gt 1001 setting secondaryTrackID in the beam command can avoid both the potential confusion and the many warnings 2 16 Signals G4beamline responds to signal SIGUSR by flushing all NTuples to disk So for a long job you can look at intermediate results G4beamline responds to signal SIGUSR2 by closing up and exiting cleanly In each worker this is detected between events This is especially useful on Hopper as SIGUSR and SIGUSR2 are the only signals users can send to the application all others cause immediate termination without saving results 1 10 14 TJR G4beamline User s Guide 30 3 Important Values that Affect the Validi
227. nally have pressure temperature state With no arguments this command prints the current material table Note that G4 is prepended to the names of most materials that are obtained from the NIST database G4 Al and Al refer to the same material unless one was previously defined using this command The following three arguments permit track filtering for all volumes made of this material keep A comma separated list of particle names to keep kill A comma separated list of particle names to kill require An expression that must evaluate nonzero or the track is killed The requir xpression uses global coordinates and can use the followng track variables X Y Z Px Py Pz t PDGid EventID TrackID ParentID wt The following materials are known from the NIST database and will be automatically created on first use H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf A 150 TISSUE ACETONE ACETYLENE ADENINE ADIPOSE TISSUE ICRP AIR ALANINE ALUMINUM OXIDE AMBER AMMONIA ANILINE ANTHRACENE B 100 BONE BAKELITE BARIUM FLUORIDE G4beamline User s Guide 66 1 10 14 TJR BARIUM S BONE
228. ned as DataPoints FreeParameters it has nHit which gives the number of trackerplane s hit Note the tracker can simulate survey errors see the set also trackerplane command for details each plane can have different errors Both the true and the fit tracks are reported at reportZ which defaults to the Z position of the tracker Note that beamlossntuple and newparticlentuple will get many entries per track when used in mode fit the fit runs the track many times through the tracker 30 100 up to maxIter NOTE the trackermode command must preceed all tracker commands in the input file and each tracker command must preceed all of its trackerplane commands The trackerZ value must also preceed all trackerplane s but reportZ can be equal to or anywhere after trackerZ G4beamline User s Guide Note that each trackerplane must have a unique name This means you should either have a separate trackerplane command for each one with unique name or use the rename argument to the place command again with unique name If you use groups for trackerplane s use rename in the group NOTE This command does not work properly in collective tracking mode Named Arguments trackerZ The Z position of the tracker Centerline mm reportzZ The Z position at which fit tracks are reported Centerline mm default trackerZ sc
229. ng line to get a white background g4ui when 4 vis viewer set background 1 1 1 display magnetic field lines fieldlines exit 1 center 0 0 0 nLines 100 five solenoids note transparency to show lines inside them coil C innerRadius 100 outerRadius 120 length 100 solenoid S coil C current 100 color 1 0 0 0 3 place S z 0 Lace z 500 Lace z 500 Lace z 1000 Lace z 1000 Pl Ppl pl Pl O UU T physics is required even though it is not used physics QGSP_ BERT 6 4 Study2Cooling g4bl Study2Cooling g4bl There are 4 Study2 cooling cells A Simpl xample g4beamline fil This version uses a Gaussian beam trace the first 10 tracks trace nTrace 10 QGSP is the default physics use case for HEP physics QGSP disable Decay beam gaussian meanMomentum 200 sigmaP 10 sigmaXp 0 01 sigmaYp 0 01 nEvents 100 beamZ 0 1 10 14 TJR G4beamline User s Guide 103 reference particle mut referenceMomentum 200 0 beamZ 0 trackcuts kineticEnergyCut 50 0 killSecondaries 1 define the solenoids use individual Focus solenoids for alternate 1 to work coil default material Cu dR 5 0 dZ 5 0 solenoid default alternate 1 color 1 1 0 coil Focusl innerRadius 330 0 outerRadius 505 0 length 167 0 maxR 330 0 coil Coupll innerRadius 770 0 outerRadius 850 0 length 330 0 maxR 770 0 solenoid USFocus coilName Focusl current 75 20 solenoid DSFocus coilName Focusl current 75 20 s
230. ng startup the version will show both the G4beamline version and your login id You can also do help mycommana or just use mycommand Some brief suggestions for writing G4beamline code 1 10 14 TJR G4beamline User s Guide 140 e Point your browser to lt install gt doc html index html this will browse the Doxygen documentation for the G4beamline classes e Class names beginning BL are G4beamline infrastructure classes e Class names beginning BLCMD are G4beamline commands e Filenames are based on the class names by appending hh or cc e Because commands are modular and independent your new feature should be packaged in a command That is your code should not do anything until and unless the input file uses your command As a bonus arguments to that command can pass user specified values to your code e There are many commands in the source Base your command on an appropriate one e Multiple features should be in multiple commands Note that even such complex features as a space charge computation are contained in a command e In general G4beamline commands are contained in a single file not referenced by any other code BLCMDphysics and BLCMDcoil are exceptions In particular there are no hh files for command classes the declarations are at the top of the cc file e All classes that implement a command are derived from BLCommand they register themselves as commands via a static initializer and their
231. nsity 1 7 C 0 213 F 0 787 material Si Z 14 A 28 086 density 2 33 material O z 8 A 15 999 density 0 001 material quartz density 2 20 Si 0 467 0 0 533 box CherenkovlFront width 400 height 400 length 1 color 1 0 0 material Al virtualdetector Cherenkovl width 400 height 400 length 20 color 0 0 1 material C6F14 box CherenkovlWindow width 400 height 400 length 2 color 0 1 0 material quartz box CherenkovlLight width 550 height 550 length 478 material Air color 1 1 1 place CherenkovlFront z 20762 9 place Cherenkovl place CherenkovlWindow place CherenkovilLight Ht The MICE cooling channel solenoids and IronShield all currents give Bz gt 0 rotation Y180 is used for Bz lt 0 HEH TRD 09 09 2005 Table 4 1 1 coil Focus innerRadius 263 outerRadius 347 length 210 maxR 263 coil Coupl innerRadius 725 outerRadius 841 length 250 maxR 725 coil Matchl innerRadius 255 outerRadius 355 length 202 maxR 255 coil Match2 innerRadius 255 outerRadius 312 length 202 maxR 255 coil Endl innerRadius 255 outerRadius 393 length 120 maxR 255 coil Center innerRadius 255 outerRadius 305 length 1260 maxR 255 coil End2 innerRadius 255 outerRadius 404 length 120 maxR 255 TRD 09 09 2005 Flip mode Case 1 Stage VI solenoid Focus coilName Focus current 113 95 solenoid Coupl coilName Coupl current 96 21 solenoid Matchl coilName Matchl current 56 30 solenoid Match2 coilName Match2 current 66 79
232. of axes at any desired location with any desired length To draw coordinate axes of 100 mm length at x 1 y 2 z 3 mm g4ui when 4 vis scene add axes 1 2 3 100 mm 2 8 1 4 Cut Away and Section Planes The Geant4 drawing interface includes cut away and section planes The interface is quirky and you ll have to search the Geant4 documentation and just play with it Not all viewers support this The commands are vis viewer set sectionPlane and vis viewer addCutawayPlane 2 8 1 5 Starting up in Wireframe Mode g4ui when 4 vis viewer set style wirefram Ww 2 8 1 6 Filters The Geant4 drawing interface includes filters that permit you to only draw certain particle types or only particles that were created in a specified physical volume or The interface is quirky and you ll have to search the Geant4 documentation and just play with it 2 8 2 The Openinventor Visualization Driver Because the OpenInventor driver OLX OTWin32 is so much more useful than the other drivers it is the driver of choice linked to the name best This driver will permit you do to almost everything that any other driver can do the exception being the Wired driver lets you modify the graphical attributes of individual objects by picking and editing that is in the works for OpenInventor Like other X windows programs the OpenInventor driver of G4beamline can operate in either local or remote networked mode The X display server usual
233. of the Motif graphical widgets The rparh libraries are for Root and are also included in the distribution 1 10 14 TJR G4beamline User s Guide 185 Appendix 5 Annotated Output from Example1 g4bl Note that Geant4 outputs considerable detail to stdout Annotations below are headings inserted into the output text First the g4bl script outputs environment variables G4BL DIR Users g4bl1 G4beamline 2 11 G4ABLADATA Users g4bl G4beamline 2 11 Geant4Data G4ABLA3 0 G4LEDATA Users g4b1 G4beamline 2 11 Geant4Data G4EMLOW6 23 G4NEUTRONHPDATA Users g4b1 G4beamline 2 11 Geant4Data G4NDL4 0 G4NEUTRONXSDATA Users g4b1 G4beamline 2 11 Geant4Data G4NEUTRONXS1 1 G4PIIDATA Users g4b1 G4beamline 2 11 Geant4Data G4PII1 3 G4LEVELGAMMADATA Users g4bl1 G4beamline 2 11 Geant4Data PhotonEvaporation2 2 G4RADIOACTIVEDATA Users g4b1 G4beamline 2 11 Geant4Data RadioactiveDecay3 4 G4REALSURFACEDATA Users g4b1 G4beamline 2 11 Geant4Data RealSurfacel 0 DYLD_LIBRARY_PATH Users g4b1 G4beamline 2 11 1lib G4beamline Process ID 30447 G4beamline outputs its identification KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK KKK KKKK g4beamline version 2 11 19 Apr 2012 17 00 Copyright Tom Roberts Muons Inc License Gnu Public License WWW http g4beamline muonsinc com KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK KKK Geant4 version Name geant4 09 05 patch 0
234. olenoid Coupl coilName Coupll current 98 25 define a detector for the center of each absorber virtualdetector Det radius 179 9 length 1 define the absorber with flat Al windows tubs Winl outerRadius 180 0 length 0 360 material Al color 0 0 1 0 0 0 tubs LH2 length 350 0 outerRadius 180 0 color 1 0 0 0 1 0 material LH2 place the virtualdetector into the absorber so its front is in the center place Det z 0 5 parent LH2 color 1 1 1 group Abs radius 0 place Winl place LH2 place Winl endgroup tune the RF Gradient tune Grad z0 100 z1 11300 initial 15 step 0 1 expr Pz1 Pz0 tolerance 0 001 define the pillbox RF cavity and put 4 of them into a linac pillbox RF innerLength 466 0 frequency 0 20125 maxGradient Grad irisRadius 160 0 winlThick 0 300 win2Thick 0 700 wallThick 5 0 winMat Be collarThick 5 0 phaseAcc 40 0 maxStep 10 0 group Linacl radius 0 place RF rename RF copies 4 endgroup define one cooling cell group Cell length 2750 0 place Abs z 1033 0 place USFocus z 1291 5 rename Focus place DSFocus z 774 5 rename Focus place Coupl z 342 0 rename Coupl place Linacl z 342 0 rename endgroup tubs Spacer length 200 outerRadius 300 material Vacuum place Spacer z 100 place 4 cells place Cell copies 4 rename C place Spacer 1 10 14 TJR G4beamline User s Guide 104 6 5 MultipleScattering g4bl MultipleScattering g4bl TJR 1 FEB 2006 mut scatterin
235. ommand Line On Linux and Mac OS X the command line is the traditional way to run programs On Windows this is possible but you must install the Cygwin environment first http www cygwin com and use its bash shell rather than the Windows cmd You can execute the G4beamline GUI in all environments via the command g4b gui executed from the install directory via an absolute path The bare g4beamline command specifies the input file plus whatever additional parameters are needed see the param command It is rarely used by users see scripts below Its syntax is g4beamline input file namel valuel name2 value2 Here input file is the filename of the file describing the simulation means stdin and namel and name2 are parameters to be passed to the program or to input file Note that users will rarely if ever execute this command directly most users will use the g4b script instead of g4beamiine itself its arguments are the same g4bl input file namel valuel name2 value2 The g4bl script will ensure that the necessary libraries from the binary distribution will be found and used and sets G4BL_DIR for finding viewer def and the physics data files Note that the g4b script relies on being executed via an absolute pathname so the distribution bin directory should be put into 1 10 14 TJR G4beamline User s Guide 8 your PATH or you can manually type the full path to g4b The g4beamline program has no such expectation but
236. on at z1 that makes the Tune particle have the desired momentum which we ll take as 1 GeV c to within 1 keV e tune Grad z0 990 z1 41010 initial 10 0 step 0 5 expr Pz1 1000 tolerance 0 001 rfdevice Cavity maxGradient Grad frequency 0 201 1 10 14 TJR G4beamline User s Guide 143 innerLength 400 place Cavity z 1000 copies 100 Note that z0 must come before the first Cavity is placed and z1 must be after the last Cavity is placed at the location where the 1 GeV c beam is desired See also section 2 11 Tuning the Beamline 1 10 14 TJR G4beamline User s Guide 144 8 Advanced Topics 8 1 Writing Scripts Using G4beamline By using parameters in your input file you can automate running G4beamline programs without having to script the editing of your input file 8 1 1 Using a Linux Cluster or Multi CPU System Because the pseudo random number generator is seeded with the Event number before the start of each event all that is necessary to run jobs in parallel is to ensure that they do not run the same events and that they write to different output files The arguments firstEvent and lastEvent to the beam command facilitate this The basic idea is to use parameters for firstEvent and lastEvent and pass them in on the command line and write a shell script to submit multiple jobs to the cluster with disjoint ranges for each job Here the output file corresponds to the first event number The input file looks like this gi
237. on evaluate to 0 0 This of course requires that some relevant beamline elements between z0 and z1 use the tune variable to change their behavior appropriately In this case we ll vary the maxGradient of all RF cavities between z0 and z1 and use an expression at z1 that makes the Tune particle have the desired momentum which we ll take as 1 GeV c to within 1 MeV c tune Grad z0 990 z1 41010 initial 10 0 step 0 5 expr Pz1 1000 tolerance 0 001 pillbox Cavity maxGradient Grad frequency 0 201 innerLength 400 place Cavity z 1000 copies 100 Note that z0 must come before the first Cavity is placed and z1 must be after the last Cavity is placed at the location where the 1 GeV c beam is desired See also section 2 11 Tuning the Beamline 1 10 14 TJR G4beamline User s Guide 132 7 22 Multiple Jobs in Parallel In many cases you will want to run multiple simulations typically scanning one or more parameters In this case it is often not necessary to run multiple jobs in parallel with or without MPI as you can simply run the different simulations on the available CPUs In this case nothing special is needed as long as you keep the different output files from clashing parameterizing the input file can help section 7 17 There certainly are situations in which multiple jobs working on a single simulation are appropriate There are two ways to run multiple G4beamline jobs in parallel all working on a single simulation 1 Manual
238. or a complete list of particle names ions can also be specified by integer PDGid Ions are supported as beam particles but only fully ionized ions and not for Root input a Root NTuple field cannot hold the PDGid Ions are specified by an integer PDGid 100ZZZAAA0 where ZZZ is the 3 digit charge protons and AAA is the 3 digit atomic number Note you must use physics processes appropriate for ions Named Arguments particle Beam particle name nEvents Number of events to process default 1 for generating events default ALL for reading files set to lastEvent firstEventtl if both are set firstEvent First event to process default is the next sequential eventID 1 if none lastEvent Last highest event to process beamX Beam location in X mm beamyY Beam location in Y mm beamZ Beam location in Z mm maxR Beam maximum radius mm rotation Rotation of the beam renumber If nonzero renumber events sequentially weight Weight for events overwritten by value from input file 1 0 secondaryTrackID The next TrackID for secondaries 1001 meanMomentum Gaussian Beam mean momentum MeV c meanP Synonym for meanMomentum P Synonym for meanMomentum sigmaX Gaussian Beam sigma in X mm sigmaY Gaussian Beam sigma in Y mm sigmaZ Gaussian Beam sigma in Z mm sigmaXp Gaussian Beam sigma in dxdz slope sigmaYp Gaussian Beam sigma in dydz slope G4beamline U
239. or spaces EXT toggle extended precision 3 more digits TAG print a gt useful to grep output N step number NSTEP Synonym of N GLOBAL X Y Z T in global coords XYZT Synonym of GLOBAL CL X Y Z dxdz dydz in CL coords CLX extended precision CL KE kinetic energy STEP step length STEPLEN Synonym of STEP VOL volume name VOLNAME Synonym of VOL PROCESS process name B magnetic field E electric field P 3 momentum MAT material name ID event ID track ID parent ID PART particle name SEG centerline coord segment number WT weight POLAR polarization NL lt newline gt NEWLINE Synonym of NL n Synonym of NL The default format is N GLOBAL CL KE STEP VOL PROCESS These names are insensitive to case See the printf command for another way to display track information and the trace command for a third 4 4 Pillbox Geometry and Dimensions The geometrical dimensions of the pillbox are given in the figure below showing a radial cross section The pipe walls and collars are always made of copper the stepped windows win1 and win2 are made of winMat and the interior of the cavity is cavityMaterial The entire pillbox is cylindrically symmetric around the beam axis The winl s the win2 s the collars the walls and the pipe can each be omitted by setting the corresponding thickness to zero 1 10 14 TJR G4beamline User s Guide 40 pipeThick I cavityMaterial innerRadius wallThick A collarRadia
240. ors can be used in expressions they evaluate to a value of 1 0 true or 0 0 false lt lt gt gt The following logical operators behave as in C amp amp DO NOT USE the bitwise operators amp as these bitwise operations behave rather strangely for double values The a b c operator is not implemented but there is a similar if a b c function The following functions can be used in expressions abs min max sqrt pow sin cos tan asin acos atan atan2 sinh cosh tanhQ exp log log10 Q floorQ ceil if All take 1 argument except min max pow and atan2 take 2 arguments and if takes 3 The following constants are pre defined pi e gamma radian 1 0 rad 1 0 degree pi 180 deg p1 180 4 2 Element Names When you create an element e g using the tubs command you must specify its name as the first positional argument When you place it into the simulated world its name must be the first positional 1 10 14 TJR G4beamline User s Guide 37 argument to the place command it can be renamed when placed Element names can be any string but conventionally obey the rules of a C identifier Element names are necessary to correlate the definition and placement of each element They are also used to report errors in the geometry test and are listed in the traces when stepping The name of a virtualdetector becomes the name of its NTuple Wh
241. ot muonsinc com which can generate histograms in a very flexible and intuitive manner from Root files and ASCII files via a graphical user interface In the future G4beamline may be extended to use other formats for NTuples as well The format ascii argument to these commands writes an ASCII file for each NTuple containing one track per line with comments at the start giving the variable names and their units The historoot program can read these ASCII files including the variable names from the initial comment Gnuplot 10 can also be used to generate plots from these ASCII files The standard fields of an NTuple generated for tracks contains the following variables in order Name Description X y Z The position of the track in the selected coordinates Millimeters 1 10 14 TJR G4beamline User s Guide 25 Px Py Pz The momentum of the track in the selected coordinates MeV c t The global time of the track Nanoseconds PDGid The ID of the particle using the assigned value from the Particle Data Group EventID The event number TrackID The track identifier ParentID The track identifier for this track s parent 0 if this is a beam track Weight The weight of the track defaults to 1 0 TrackIDs are supposed to be unique within each event they normally start at 1 for the beam particle s Secondary particles TrackIDs normally start at 1000 and increment sequentially
242. our needs the example is quite silly and unphysical it is intended only to show what can be done Things to remember e The source files to be compiled are arguments to g4blmake they default to cc cpp C i e the common extensions for C source files e Any additional libraries your code requires can be passed in the environment variable EXTRALIBS or can be simply appended to the g4b make command line e Any additional compiler flags e g I some dir can be passed in the environment variable CPPFLAGS e Your filter code must implement a class derived from UserTrackFilter and must have a static instance to register it with G4beamline 1 10 14 TJR G4beamline User s Guide 151 e Read the comments in UserTrackFilter hh to understand the interface to G4beamline and to see what types of things your code can do e More than one derived class can be defined in the source files either in a single cc file or in separate cc files They must have different filterName s e You can add other libraries if you wish For example your class could query an external database indexed by eventID and trackID and kill unwanted tracks as indicated by the database To do that your class would connect to the database in setup query it in filter and disconnect in complete e It s best to keep your code simple as it is rather difficult to debug large programs like G4beamline 8 5 Multiple Instances of G4beamline using MPI The Messag
243. p if necessary When finished save the file to disk without exiting the editor 2 W1 G4beamline GUI If input file is not already selected do so with the Browse button Push the Run button to run the simulation If there was an error go back to step 1 1 10 14 TJR G4beamline User s Guide 121 3 W4 historoot do File OpenFile and open g4beamline root or whatever file the simulation wrote Select the desired NTuple and push CreatePlot the plot configuration will remain from the previous iteration 4 W4 historoot do File CloseAllFiles This is important to avoid confusion On Windows this is essential because if historoot has the root file open g4beamline won t be able to write to it and the next step 2 will fail for that reason 5 Examine the plot and determine what to do next Go back to step 1 7 9 Putting Shielding into a Simulation G4beamline is a realistic simulation program and just like a real beamline one must provide appropriate shielding While obviously there are no radiation issues in a simulation it is necessary to provide shielding that is sufficient to prevent particles from traveling in unexpected places This is particularly troublesome for secondary particles from decays and interactions as they often have sufficient transverse momentum to quickly leave many beamline apertures and even get outside the outer dimensions of magnets Particles that go in unexpected places and directions can confuse plots an
244. parent s coordinate axes 2 Rotate the object and its local coordinate axes by 90 degrees around the parent s Y axis 3 Then rotate the object and its local coordinate axes by 30 degrees around the parent s X axis Negative and decimal values of the angle are permitted The direction of a positive rotation is given by the right hand rule use your right hand to grasp the rotation axis with your thumb in its positive direction a positive rotation goes in the direction of your fingers G4beamline User s Guide 16 If both a rotation and an offset are specified when placing an element the rotation occurs first then the offset This makes sense as the location of the center of the object is specified when placing objects When the parent is placed with a rotation and or an offset the relationship between daughter and parent remains unchanged so the effect on the daughter is cumulative all the way back to the World volume When used in a corner or cornerarc command the rotation is relative to the previous centerline coordinates When placing into the World volume using centerline coordinates the rotation is relative to the current centerline coordinates as is natural So for example one can simply place genericquad elements using centerline coordinates without rotation or offset and the nominal beam centerline will go right down their center Note this is quite different from the way the Geant4 toolkit itself specifies rotation
245. particles currently known particles processes currently known physics processes NOTE the particles and processes lists are not populated until the physics list is selected via the physics command Different physics lists use different processes and particles G4beamline User s Guide 65 man material 1 10 14 TJR NOTE listing processes will prevent any simulating as will a non empty particle list Named Arguments particle Comma separated list of particles for which details will be printed Alias for help construct a new material This is an interface to G4Material This command is rarely required becaus lements and most common materials are available via the NIST database Any material available from the NIST database can simply be used if it is unknown then it will be automatically defined from the database Uncommon materials or nonstandard densities must be defined with this command The first argument to this command is the material name which is always required density is also required The command to define an element e g with non standard density is material H2 Z 1 A 1 01 density 0 000090 A mixture or compound is a combination of known materials and or elements the command is material water H 0 1119 0 0 8881 density 1 0 The numbers following the element names are their mass fractions note that WATER is available from the NIST db Either type of command can optio
246. polarization in the file overwrites the value from the command line Note the original BLTrackFile format is supported but the additional fields are not present Note also that properTime pathLength initialPosition initialT and initialKE are for THIS simulation and their values in the file are ignored Root beams are read from a root file using the TNtuple named directory name in the file It must have the same fields as used in BLTrackFile2 format Note that EventIDs greater than 1 10 14 TJR G4beamline User s Guide 46 1 10 14 TJR 16 777 216 will be rounded When reading a file ascii or root beamX and beamY are added to input tracks if beamZ is set it will overwrite the z of the track but if it is not set the z of the track in the file is kept All coordinates are centerline coordinates Multiple beam commands can be given and they will generate events in the order they appear in input file Events are generated starting at firstEvent until either nEvents have been generated or lastEvent would be exceeded Beam tracks with momentum 0 will take one step as a stoppd particle as desired For gaussian rectangular and ellipse beams the beam particle can be given as either a particle name or its integer PDGid Some common beam particle names are proton anti proton pit pi mut mu et e kaont kaon kaonO nu e anti_nu_e See the User s Guide f
247. r BLCMDvir BLCMDvir tual tua tual ldetector ldetector ldetector Cua ldetector Construct Construct Construct Construct Detl Det2 Det3 Det4 A comment from the Geant4 Physics List Addi The Geometry test results 1 10 14 TJR ng tracking cuts for neutron 1Z 1000 1Z2 2000 12 3000 1Z2 4000 lobZ 1000 lobZ 2000 lobZ 3000 lobzZz 4000 parent parent parent parent re Le ES ES coo o QaQqgaga OOo TimeCut ns 10000 KinEnergyCut Mev 0 G4beamline User s Guide 187 Geometry test nPoints 100 tolerance 0 002 mm Testing geometry for children of group World Total geometry errors 0 0 seconds Now the Tune Particle is prepared and simulated nothing to tune in this simulation Prepare Tune Particle s xxx NOTE All stochastic processes are disabled Begin Tune Particle s Run complete 1 Events 0 seconds The Reference Particle is tracked Begin Reference Particle s Run complete 1 Events 0 seconds Stochastic processes are enabled after the reference particle Stochastic processes ar nabled Preparation to track the beam Prepare Tracking Beam Stochastic processes ar nabled And the beam is tracked timing summaries are spaced out to avoid too much output Begin Tracking Beam
248. r Every element accepts an argument color 1 1 1 where the 3 floating point values are for Red Green Blue respectively and must be between 0 0 and 1 0 inclusive color invisible or color is invisible color 1 1 1 is white color 0 0 0 is black color 0 1 1 is yellow color 0 6 0 6 0 6 is gray etc Most elements have a default color of white An optional fourth value alpha can be given it must be between 0 0 and 1 0 inclusive and represents the transparency of the element 0 transparent 1 opaque Transparency can be very useful as it permits you to see tracks inside objects a wireframe view will also permit that but has many extraneous lines that confuse the eye By default particle tracks are visible red for negatives blue for positives and green for neutrals See the particlecolor command to change this If you run pions or muons you may be surprised to see all the neutrinos from their decays see the trackcuts command to avoid tracking them You may also be surprised by delta rays which are really low energy electrons e trackcuts can eliminate them too For example when studying z 1 e decays the following commands are useful to color them differently and to eliminate the neutrinos and other extraneous particles e g delta rays particlecolor pit 1 0 0 mu 0 1 0 e 0 0 1 trackcuts keep pit mut e 1 10 14 TJR G4beamline User s Guide 18 Once your
249. r that generates an NTuple zntuple Generate an NTuple for each of a list of Z positions Physics commands bug1021 Workaround to improve accuracy of bug1l021 in E field emfactor Multiply multiple scattering and energy loss by factors muminuscapturefix Fixes up the G4MuonMinusCaptureAtRest process physics Defines the physics processes and controls them reweightprocess modify the cross section of a physics process setdecay Set lifetime decay channels and branching ratios for a particle s decay Spacecharge Beam frame Green s function space charge computation spacechargelw Lienard Wiechert space charge computation Other commands collective Monitor collective computation demo demo command 1 10 14 TJR G4beamline User s Guide 44 fieldlines Display magnetic field lines label Display labels or markers visually in 3 D space movie Generate movie NTuple survey survey command test test random number seeds Program control Parameters zcl Last centerline Z position used updated continuously deltaChord Geant4 tracking parameter deltaIntersection Geant4 tracking parameter deltaOneStep Geant4 tracking parameter epsMax Geant4 tracking parameter epsMin Geant4 tracking parameter eventTimeLimit CPU Time Limit sec fieldVoxels Size of voxels for field computation mm histoFile Default Root NTuple output filename histoUpdate Output update interval events maxStep Maximum physics step size mm minStep Minimum step size
250. r weight of tracks e Create secondary tracks Doing this requires e G4beamline built from source on your system e A basic understanding of how to write and compile C code e On Windows the Cygwin system must be installed e Onall OSs a command line window is used The basic idea is to compile your code directly into G4beamline An example is provided in the directory UserCode in the G4beamline installation directory if you don t know where that is type the command g4bl dir It contains the following files Filename Description ExampleFilter cc Code for the example filter test in Input file to test the example filter These instructions are for the bash shell modify them appropriately for other shells These are all basic UNIX commands and if you don t understand them you probably need the assistance of someone more experienced in UNIX and C code development After installing and building G4beamline from source see the appendices BUILD txt and the README files you should first try running the example cd directory for your simulation mkdir UserTrackFilter cp g4bl dir UserCode g4blmake export G4BEAMLINE PWD g4beamline g4bl test in This last command should end by printing Run complete 10 Events 0 seconds ExampleFilter complete killed 6 tracks created 51 tracks ExampleFilter complete killed 6 tracks created 51 tracks Once the example works you can modify it to suit y
251. rackFile and the Trace file above 1 10 14 TJR G4beamline User s Guide 175 10 Acknowledgments The genesis of G4beamline was my desire to learn modern physics simulation codes and Geant4 seemed to be the best choice Parts of G4beamline s design were inspired by the Beam Tools developed at Fermilab 6 by Daniel Elvira Paul Lebrun Panagiotis Spentzouris and others even though almost none of their code remains The LISAPhysicsList came from the Geant4 collaboration and the MICEPhysicsList came from G4MICE developed by the MICE collaboration The source files from these external sources retain the original authors comments and disclaimers they total less than 1 of the G4beamline source code Geant4 1 is a flexible and versatile toolkit for simulating the passage of particles through matter and electromagnetic fields This program literally would not have been possible without it Thanks to the entire Geant4 collaboration This product includes software developed by Members of the Geant4 Collaboration http cern ch geant4 CLHEP 2 is a comprehensive class library for High Energy Physics and G4beamline literally would not have been possible without it Thanks to all of the CLHEP editors and authors The HistoScope program 3 is a marvelous program for generating and manipulating histograms It has a fine graphical user interface and can do just about everything one might want to do with histograms X Y plots scatter plot
252. ram command is unique in that when the value of any argument is a valid numerical expression containing at least one operator the expression will be evaluated and the parameter will be defined as the number rather than the string of the expression This permits the computation of rotations the value of the rotation argument is a string containing multiple numerical values param angle atan2 Sa S b 180 3 14159 place Element rotation XSangle Y90 4 1 Expressions Expressions can be used for the value of any integer or double argument to any command They are evaluated during command processing and generally must involve only double values and the operators and functions listed below Parameter expansion paramname can be used as long as the string value of paramname is valid where it appears in the expression Some commands expand the expressions to include certain variables e g the Bx argument to fieldexpr can be an expression involving x y z In the param command if the value of an argument is a valid numerical expression the parameter is set to the numerical value rather than to the expression string All values are doubles for integer parameters the conversion occurs after the expression is evaluated The following arithmetic operators can be used in expressions Note that means exponentiation to an integer power use pow for a double exponent Note that is not implemented The following comparison operat
253. re the expressions x Expression involving the track variables to plot horizontally Variables x y z Px Py Pz t PDGid EventID TrackID ParentID Weight The standard C functions and operators can be used y Expression involving the track variables to plot vertically xMin Left limit of the plot in whatever coordinates are used by x xMax Right limit of the plot in whatever coordinates are used by x yMin Bottom limit of the plot in whatever coordinates are used by y yMax Top limit of the plot in whatever coordinates are used by y background Color of the background setup value textHeight Height of text in pixels If omitted the value from the setup command is used sideview Displays a side view of the apparatus using Reference Coordinates with a moving marker that indicates where the reference particle is located at the current time markerSize The relative size of the marker 1 0 filename The name of the Root file to use If omitted uses the most recently opened Root file i e from the previous command Note the NTuple names to use are fixed Movie Reference and Movie Elements zMin Left limit of the plot in Reference Coordinates synonym is xMin zMax Right limit of the plot in Reference Coordinates synonym is xMax yMin Bottom limit of the plot in Reference Coordinates yMax Top limit of the plot in Reference Coordinates title Title of the view textHeight Height of text in pixels setup
254. rement Z by dZ the first line in a block is for Y YO and the first column in each line is for X X0 For cylinder maps the first line in each block is for Z Z0 and the first column in each line is for R 0 Instead of the blocked input format a pointwise data format can be used This is introduced by a line containing the command data followed by the individual points of the map one per line for a grid field each line contains values for X Y Z Bx By Bz Ex Ey Ez separated by either a comma and optional whitespece or by whitespace for a cylinder field each line contains values for R Z Br Bz Er Ez The order of the points does not matter omitted grid points will be 0 0 and for duplicates the last entry wins If there is no E field the Ex Ey Ez or Er Ez entries should be omitted on every line NOTE every line s X Y Z or R Z must be on a grid point as specified by the arguments to the grid or cylinder commands to within the tolerance specified if not an error message is printed and the input line is ignored For time dependent fields the time command is used time period 12 period if given is in nanoseconds and causes the interval 0 period to b xtended forever before and after the values given Because of the interpolation used at least two points beyond the interval boundaries should be provided there need not be a point at either boundar
255. rid interval is 1 cm The region of validity is 390 lt Z lt 390 and 0 lt R lt 90 param normB 1 0 current 1 0 Linder Z0 0 0 nR 10 nZ 40 dR 10 0 dZ 10 0 extendZ flip Br data 400 lines of 4 values giving R Z Br Bz EOF 9 5 Window Files Used by the absorber command This x The file format is a series of lines First character means comment means printed comment Comment and blank lines are ignored Units are mm The first line contains the 4 flange variables innerR outerR insideZ outsideZ The remaining lines contain 3 values for a given radius rzt The first line must have r 0 0 and have the largest z value and the largest z t value z is the inside of the window z t is the outside of the window All values must be positive Successive r values must increase by at least 0 010 mm Successive z values and z t values must decrease by at least 0 010 mm flangeInnerRadius should equal the last r value Any z origin may be used it will be subtracted away is intended to be easy to interface to window design spreadsheets export a list of 3 columns delimited by spaces then add the appropriate comments and flange values at the top 9 6 Root Files The standard Root file format is used All G4beamline outputs are TNtuple s combined into a single Root file whose name is given by the parameter histoFile The TNtuple fields are the same as for BLT
256. ring excitation and fragmentation Uses Geant4 Bertini cascade for primary protons neutrons pions and Kaons below 10GeV ERT TRV A variant of FTFP_BERT where the Geant4 Bertini cascade is only used for particles below 5 5 GeV ae wW eal P BERT HP No synopsis available BIC No synopsis available For low background experiments e g underground P For calorimetry is the fastest when it comes to CPU It uses the LEP and HEP parametrized models for inelastic scattering The modeling parametrizes the final states individual inelastic reactions so you will not see G4beamline User s Guide pillbox 1 10 14 TJR resonance distribut s and the detailed secondary angular ions for O 100MeV reactions may not be described perfectly The average quantities will be well described QBBC No synops QGSC_BERT For ca as QGSP f invariant to model Geant4 Be reactions QGSP For calor high ener theory dr pions ka model for projectil cross sec approxima extensive nucleus cross sec QGSP_BERT Like Q protons compariso to data c parameter 7 is available lorimetry and high energy physics trackers is or the initial reaction but uses chiral phase space decay multi quasmon fragmentation the behavior of the system s fragmentation Uses rtini cascade for nucleon and pion induced imetry and high energy physics trackers and gy and medium energy production targets
257. rob G4beamline 2 14 lib libMathCore so 0x0043d000 libNet so gt home tjrob G4beamline 2 14 lib libNet so 0x00186000 libRIO so gt home tjrob G4beamline 2 14 lib 1libRIO so 0x009cb000 libThread so gt home tjrob G4beamline 2 14 lib libThread so 0x00119000 libTree so gt home tjrob G4beamline 2 14 lib libTree so 0x00b45000 libexpat so 0 gt usr lib libexpat so 0 0x0028a000 libdl so 2 gt lib libdl so 2 0x002df000 libstdc so 6 gt usr lib libstdc so 6 0x0297d000 libm so 6 gt lib tls libm so 6 0x002ba000 1 10 14 TJR G4beamline User s Guide 181 libgcec_s so l gt lib libgcc_s so 1 0x0015c000 libec so 6 gt lib tls libc so 6 0x06242000 libpthread so libxxf86vm so libXp so 6 gt libcrypt so 1 lib 1d linux 0 gt lib tls libpthread so 0 0x00402000 1 gt usr X11R6 lib libxXxf 86vm so 1 0x00101000 usr X11R6 lib libXp so 6 0x003d6000 gt lib libcrypt so 1 0x005e0000 so 2 0x0016e000 Note that some motif X11 shared libraries are included in the G4beamline distribution and remain local to it This reduces the need for users to install precisely the same version of these libraries as was used to build g4beamline Here are the RPMs that provide these libraries in Scientific Linux Fermi 4 8 glibc i686 glibc i686 xorg x11 Mesa libGLU i386 xorg x11 Mesa libGL i386 openmotif i386 xorg xll libs xorg x1ll libs xorg x1ll libs xorg x1ll libs
258. root muonsinc com Cygwin http cygwin com This is a UNIX like command line environment for Windows Select Install Cygwin now This will download Cygwin s setup exe Run it select a mirror site and you will have the opportunity to select packages You should select at least one editor of your choice vi emacs or You must also select tcltk which is in the Libs category You can add or remove packages at any time by re running the Cygwin setup exe Install it into the default directory C cygwin To install G4beamline download G4beamline 2 14 msi and run it Follow the usual directions for installing packages into Windows The installer will install shortcuts for G4beamline and Historoot onto your desktop and into the Start menu If you have installed Cygwin then if you want to run G4beamline from its command line do this in a Cygwin shell source C Program Files MuonsInc G4beamline bin g4bl setup sh The puts G4beamline into your PATH Then do cd wherever g4bl input file name value The default format for NTuples is now Root To create histograms from NTuples you can use Root in the usual way That is rather complicated and un obvious so you can download the HistoRoot program from http historoot muonsinc com For visualization the OpenInventor viewer works fine simply select best from the viewer panel of the G4beamline window Other viewers are available 1 10 14 TJR G4beamline User s Gu
259. rors When a parameter that has not been defined is used it will be automatically defined from the environment if possible otherwise using an undefined parameter generates an error this is especially useful in Grid jobs which may need O0SG_WN_TMP in every filename A parameter can be used in the value of any argument to any command tubs Name length Slength outerRadius Sradius In this example it is necessary to define the parameters ength and radius before this command is issued that can be either earlier in the input file or on the command line Here the string definitions of both parameters ength and radius must be valid floating point numbers or expressions earlier in the input file param length 100 0 radius 10 0 Or on the command line g4bl input file length 100 0 radius 10 0 Note that once the parameter is defined it can be used any number of times to give the values of command arguments That can be used to avoid having to change many identical numerical values 1 10 14 TJR G4beamline User s Guide 38 throughout the input file It can also be used to collect all of the variable values of input file in one place near the top or even in a separate definition file see the include command This is a limited macro facility and can only be used to substitute the string value of a parameter into a command argument named or positional For integer and double real arguments arithmetic expressions involv
260. rticle enters the timingVolume but many leave it It is important the maxStep used by the tracking not be too large The default value is usually too large while 1mm seems to work well If the state is ATWORKING OFFSET the 1 pass is done with timingZero 0 the 2 at 90 RF later The output AE A t tarif or AO may be approximated as O A sin ot so taking the first two passes O A sin O A sin n 2 A cos gives O atan O O gt A V O 03 rfdeviceField UserSteppingAction algorithm logic states timing state description ATWORKING_ UNKNOWN initial state no processing done yet ATWORKING_ OFFSET multiple pass search defines 0 RF ATWORKING BYPASS iff total timing explicitly fixed ATWORKING BASE single pass at 0 RF ATWORKING ESTIMATE 1 estimate to match requirements ATWORKING FINETUNE fine adjustments to match requirements ATWORKING_ FINAL final pass with final parameters ATWORKING_DONE complete state all processing done 1 10 14 TJR G4beamline User s Guide 163 UNKNOWN BYPASS lt gt N fime Offset fixed CDE adjust max Gradient ESTIMATE FINETUNE J A FINAL 1 10 14 TJR G4beamline User s Guide 164 When using timingMethod atZlocal the 3 pass onward during state ATWORKING OFFSET adjusts the arrival time at timingAtZ to be 90 RF for a positive particl
261. rticles will decay and interact generating secondary particles Without such a cut secondary particles can greatly confuse the interpretation of a plot HistoRoot has a specific feature to display the particle types put PDGid into the Particle Type field and whenever the NTuple is scanned to generate the plot a list of the PDGid s contained within the slider cuts will be printed with names for common particles To display a bundle of tracks put trace nTrace 100 format ascii oneNTuple 1 into your input file and then use gnuplot to plot the AllTracks txt file that G4beamline wrote gnuplot omits the back trace line between tracks because the trace command puts a blank line between tracks specifically for this gnuplot is available for Linux as part of the distribution for Mac OS via Fink and for Windows via http www gnuplot info HistoRoot HistoRoot requires Root to be installed and for best results install the version of Root available from http historoot muonsinc com By default all NTuples generated by G4beamline are placed into a single Root file Note however that HistoRoot can also read the ASCII NTuple files written by G4beamline and other programs see the HistoRoot Help for the file formats accepted Generating plots and histograms is straightforward and the help for HistoRoot should permit you to get started right away You can quickly and easily plot arbitrary expressions of the NTuple s fields
262. ry test has a default tolerance of 2 microns in practice these are usually reasonable values but they can be changed when required by simulations at a different scale Note that the Geant4 toolkit has logical volumes physical volumes and placements In G4beamline these are not visible to the user elements are modeled as single objects and you simply place the objects where they belong keeping in mind the above requirements on intersections The C Tybs is the name Geant4 uses for a tube or a cylinder a tube with innerRadius 0 1 10 14 TJR G4beamline User s Guide 12 code implementing each element deals with the Geant4 details of course Unlike Geant4 in G4beamline an element that generates an electromagnetic field is a single object that includes both its geometrical volume s and its field An additional limitation of the geometry in G4beamline is the requirement that any element that is to be the parent of other elements be placed after the children are placed into it Once a given element has been placed anywhere it can no longer be used as the parent of other elements 2 4 Coordinates There are four types of coordinates used in G4beamline 1 Global coordinates 2 Local coordinates 3 Centerline coordinates 4 Reference coordinates All coordinate systems are Cartesian with axes labeled X Y Z T For geometrical placement T is irrelevant but it is needed during tracking X Y Z are always righ
263. ry track that enters Print total energy deposited in selected volumes At end of run prints the total energy deposited in the selected volumes Volume name patterns are like UNIX filename patterns Sis AB matches any name containing an A or a B Tracks that are killed have their kinetic energy summed into the volume where they were killed unless they are killed becaus they leave the World With ancestors 1 energy deposited in matching volumes is added into their ancestors energy deposited directly into those ancestors is not summed into them unless their names also match That is if A is a child of B but only A matches the list of volume names energy deposited into A will be reported in both A and B but energy deposited directly into B is ignored G4beamline User s Guide 90 Named Arguments volumes Comma separated list of Volume Name patterns ancestors Set nonzero to sum energy into all ancestor enclosing volumess 0 enclosing Synonym for ancestors filename Filename to write summary stdout file Synonym for filename trace Specifies tracing of tracks Generates a separate NTuple for each track with 1 row per step unless oneNTuple is nonzero in which case all tracks are put into a single NTuple So format ascii generates one file per track with names generated by the pattern in filename first d is replaced by event second d is
264. s PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 The following additional fields are appended for format Extended format asciiExtended and format rootExtended Bx By Bz Tesla Ex Ey Ez Megavolts meter ProperTime ns PathLength mm PolX PolY PolZ polarization InitX initY InitZ initial position mm InitT initial time ns InitKE MeV when track was created Valid Formats ignore case ascii bltrackfile dummy for009 for009 dat root trackfile Extended asciiExtended rootExtended Named Arguments cannot be changed in place cmd Z Comma separated list of Z positions mm zloop Loop in z first last incr mm noSingles Set to 1 to omit the NTuple for singles format NTuple format see above for list file Output filename uses name to determin G4beamline User s Guide 99 filename filename Synonym for file require Expression which must be nonzero to include the track default 1 referenceParticle Set to 1 to include the Reference Particle coordinates Coordinates global centerline or reference default c 1 10 14 TJR G4beamline User s Guide 100 6 Examples On Linux and Mac OS the examples are found in the examples directory under the install directory On Windows they are found there also and a copy is pl
265. s 1l e 3 verbose Set nonzero to show timing volume and print info messages 1 fieldMapFile Filename for BLFieldMap pillbox if null kill Set nonzero to kill tracks that hit the pipe walls or collars 0 setdecay Set lifetime decay channels and branching ratios for a particle s decay The particle is specified by name as the first positional argument 1 10 14 TJR G4beamline User s Guide 84 showmaterial solenoid spacecharge 1 10 14 TJR The lifetime of the particle can be set unless it is a short lived particle for which lifetime is fixed at 0 these are particles like quarks Zs and Ws Units are ns Decay channels are specified daughterl daughter2 BR where the daughter names are separated by commas and the branching ratio is a value between 0 and 1 inclusive the order of daughters does not matter The sum of all BRs must be 1 0 It is best to use existing channels for the particle because the code for the decay distribution is retained new decay channels are given a default phase space distribution which is probably valid only for a 2 body decay of a spin 0 particle New channels are limited to 4 daughters Note that all desired decay channels must be listed Example to force fast decay 0 1 ns of pi to a positron setdecay pit lifetime 0 1 e nu_e 1 0 Set the colors for selected materials
266. s 2 d histograms and NTuples Much thanks to the authors Mark Edel Konstantine Iourha Joy Kyriakopulos Paul Lebrun Jeff Kallenbach and Baolin Ren thanks also to Fermilab for making it available Unfortunately it is no longer supported It was the inspiration for HistoRoot Root 5 is a programming environment intended for data analysis It supports data files with a tree structure 1 D and 2 D histograms X Y plots and NTuples Accompanying G4beamline is historoot a root program that provides a graphical user interface to the histogram capabilities of Root it was inspired by the capabilities of HistoScope with a completely different user interface Of course the native Root tools can be used as well Thanks to all of the Root developers The Coin 3 D graphics library 9 is licensed under the Gnu Public License maintained by Kongsberg SIM AS This implements by far the best visualization driver for simulated systems and events The X windows graphics libraries and the basic gcc libraries and compiler are also released under the GPL and or LGPL Thanks to the entire open source community for making such a comprehensive software development environment freely available 1 10 14 TJR G4beamline User s Guide 176 Appendix 1 README txt G4beamline by Tom Roberts Copyright C 2003 2012 by Tom Roberts All rights reserved http g4beamline muonsinc com LICENSE This program is free software you can redistribute it an
267. s In particular it is not possible for users to implement a new physics process in G4beamline without building the program yourself that is rather complicated but you can request a new feature to have us do it see section 7 3 The physics list is selected by the physics command and the set of available lists is given in the help text for that command see section 7 4 As atule of thumb for incident particles with kinetic energies above 12 GeV or so the standard physics list is FTFP For incident particles with kinetic energies above about 100 MeV the standard physics list is FTFP_BERT it is noticeably slower than FTFP below 12 GeV The electromagnetic processes of these physics lists are advertised to be valid above a few hundred electron Volts Geant4 has a set of low energy electromagnetic processes indicated by a suffix _ EMX in the physics list name The suffix EMV indicates electromagnetic processes tuned for better CPU performance with only slightly less precision 3 2 Tracking Accuracy Parameters There are a number of values in Geant4 that affect the accuracy of its tracking The important ones are implemented in G4beamline as parameters and they can be set anywhere in your input file with the param command the final value is what matters These control such things as how close to a geometric boundary a track must come before it is considered to have hit the volume how far a track can deviate from a
268. s see figures below Global Coordinates view Z vs X Each track makes 6 1 2 circles that lay right on top of each other X 0 2 0 Beam generated straight up 100 events 1 10 14 TJR G4beamline User s Guide 15 Ww 20 Se B 2 gt gt X D D 10 gt gt CQ A y Ce EKK S _ a 20 a es m paaa 500 1000 2 5 Rotations CCI Reference Coordinates view Z vs X allTracks txt using 3 1 A ai gt gt gt _ gt K gt gt gt gt 50 gt EK gt KK D gt gt gt gt gt gt gt ECE gt EK X ee a lt 1500 2000 2500 3000 3500 In G4beamline all rotations are specified relative to the fixed coordinate axes of the parent volume into which a given element is being placed This is the natural way to think of placing an object into a room where the object is the element being placed and the room is the parent volume into which it is placed Rotations can be specified in the place command and in a few other commands They are specified by a rotation parameter the value of which is a comma separated list of rotations around the parent s coordinate axes which are applied in order left to right to the object values are in degrees So rotation Y90 X30 means 1 10 14 TJR 1 Start with the object s local coordinate axes aligned with the
269. s a logical combination of its trackerplanes the tracker cannot be placed but its trackerplanes must be placed into the system The fitting algorithm used requires that all of its parameters have comparable scales so the scaleX scaleXp scalePtot and scaleT arguments should be set to the approximate sigmas of the tracker They should be within a factor of 10 of the actual values but closer is better At the end of fitting tracks a summary is printed that flags each parameter with RESCALE if its scale is too different from its sigma factor of 5 or more NOTE if the tracker cannot measure Ptot then scalePtot MUST be set to zero If the tracker cannot measure T then scaleT MUST be set to zero Parameters with zero scales are held fixed at their true track values NOTE the trackerplane s of a tracker MUST be placed in the order that particles will hit them the code does not sort them Usually this means that each place command of a trackerplane must have a larger z value than the previous place command They must 1 10 14 TJR G4beamline User s Guide 92 true_Px 1 10 14 TJR also come after the trackerZ value of the tracker command A tracker has 3 modes of operation true Each track of each event is written to a the NTuple includes both the true track values TrackerHits NTuple if it hits all trackerplanes and the individual w
270. s an rfdevice RF cavity solenoid defines a solenoid a coil and current sphere construct a sphere or section of one tess Alias for tessellatedsolid tessellatedsolid construct a tessellatedsolid torus construct a torus trap construct a solid trapezoid with axis along z tube Alias for tubs tubs construct a tube or cylinder with axis along z The place command place places an element into the current group or world Track and Event cuts eventcuts Implements cuts on event number via lists in files trackcuts Specifies per track cuts Data output commands beamlossntuple NTuple containing particle tracks when lost detector Construct a Detector that generates an NTuple fieldntuple Generates an NTuple from B and E fields at specified points newparticlentuple NTuple containing particle tracks when created ntuple Define an NTuple containing multiple detectors printf prints track variables and expressions printfield Prints E or B fields or writes FieldMap file probefield Prints B and E fields at specified points profile write beam profile information to a file timentuple Construct an NTuple of tracks at a specified time totalenergy Print total energy deposited in selected volumes trace Specifies tracing of tracks tracker Defines a tracker trackerplane Construct a tracker plane usertrackfilter Construct a usertrackfilter that filters tracks via user code virtualdetector Construct a VirtualDetecto
271. s and placements 2 6 Materials Every physical object inherently is constructed out of some material G4beamline uses the Geant4 methods of specifying materials The Geant4 version of the NIST database is available and is used to define any material that is not already defined as long as it is known to the database This database includes all elements with Z lt 98 plus a rather large list of other materials including most of the ones commonly used in simulations See help material for details or the material command in section 4 below Additional materials can be defined as needed via the material command but that is needed only for unusual materials or gases with nonstandard density The Geant4 NIST database prepends G4_ to all material names but in G4beamline that prefix is optional G4_Al and Al are the same material aluminum from the NIST database Every element command has a material argument or similar to set the material for the physical object some elements have more than one kind of material parameter In many cases the default is that of the parent volume but refer to the individual command descriptions for the actual default values The material of the World volume is determined by the parameter worldMaterial which defaults to Vacuum Materials defined by the material command can be used to filter particle tracks That is the user can specify which types of particles will be killed whenever they enter any obje
272. se o csecc assent vecaune aia vae iets atesee ectaalss 120 7 7 Basic Execution in a Command Line Environment cccceeccecseesseceseceeeeeeseeeseeceaeceseeeeeeenaees 120 7 8 Basic Execution in a GUI Environment 3 552 pcccaxeaseesatuasandlatesavadanedanes desoaaevecs dans inceoawetandanoiassaara 121 7 9 Putting Shielding into a Simulation sseseesseeseeseesseessesesssressessrssessessresresseeseesesseesesrrssessesees 122 7 10 How to Debug a Simulation s ssssessseeseesessseessesesssessesresstessessrsstessesstsstesseeseesresseessesrrsseessesees 123 TAL Gents Command S a aureo r EE ia a E AE EE AE E e pias hime EDA 124 7 12 Obtaining Plots and Histograms ss sssseeeseeseeseesseessesressressessrssessesstesresseesessrsseessesrrsseessesets 124 7 13 Obtaining Pictures of the System and Events iss soncecscsfacchetecesusccsshs ches anuedoscdanusacgevaaterascaveseestsss 125 7 14 Warning and Error messages Which Ones can be ignored s ssesseessssseessesessseesseserssressesers 126 7 15 Secondary Tracks and Particles a csccesssedactsskssinegsunseceyhaesseyscoteituacts ies earn edvwerloictae duals 127 7 16 Finding Example Input Files using the XXX command 2 0 0 ceeeeeseeeeceeeceeeeneeeeeeseeeeeeeenaes 128 7 17 Parameterizing the Input Pines ood 9 otal usl ah cea ah 2 oe al ale ean eae acl amleas a enruns 128 7 18 Setting Fields of Magnets sessssseesseesssssesseossossrsseossessesseessessosseesseosossoesseessesoesseesses
273. sec Event 800 Completed 800 events realTime 1 sec 800 0 ev sec Event 900 Completed 900 events realTime 1 sec 900 0 ev sec Event 1000 Completed 1000 events realTime 1 sec 1000 0 ev sec Finally the run is finished a summary of NTuples is printed Run complete 1000 Events 1 seconds NTuple Detl 1002 entries NTuple Det2 1003 entries NTuple Det3 999 entries 1 10 14 TJR G4beamline User s Guide 188 NTuple Det4 953 entries NTuple wrote Root File g4beamline root A summary of all Exceptions is printed a list of how many of each type is also printed Exceptions 0 Fatal 0 Events Aborted 0 Stuck Tracks stopped 0 Warnings The simulation is over g4beamline simulation complete exiting 1 10 14 TJR G4beamline User s Guide 189 Appendix 6 Particle IDs B B BO Bs0O D D DO Dst Ds Generic Ion He3 J psi N 1440 N 1440 0 N 1520 N 1520 0 N 1535 N 1535 0 N 1650 N 1650 0 N 1675 N 1675 0 N 1680 N 1680 0 N 1700 N 1700 0 N 1710 N 1710 0 N 1720 N 1720 0 N 1900 N 1900 0 N 1990 N 1990 0 N 2090 N 2090 0 N 2190 N 2190 0 N 2220 N 2220 0 N 2250 N 2250 0 a0 1450 a0 1450 a0 1450 0 a0 980 a0 980 a0 980 0 al 1260 al 1260 al 1260 0 a2 1320 1 10 14 TJR PDGid 521 PDGid 521 PDGid 511 PDGid 531 PDGid 411 PDGid 411 PDGid 421 PDGid 431 PDGid 431 PDGid 0 PDGid 1000020030 PDGid 443 PDGid 12212 PDGid 12112 PDGid 2
274. ser s Guide 47 sigmaP sigmaT sigmaE meanXp meanYp meanT polarization beamHeight beamWidth filename file directory category uid name format beamxXp beamYp eV c s Gaussian Beam sigma in P Gaussian Beam sigma in T Dos Elliptical Beam sigma in E MeV Gaussian Beam mean in Xp slope Gaussian Beam mean in Yp slope Gaussian Beam mean in T ns Polarization 3 vector 0 0 0 Rectangular Beam height mm Rectangular Beam width mm input file name synonym for filename Root file directory of NTuple Deprecated synonym for directory HistoScope uid of NTuple Root name of NTuple ASCII file format Default BLTrackFile Synonym for meanxXp Synonym for meanYp beamlossntuple NTuple containing particle tracks when lost 1 10 14 TJR All possible are omitted but mechanisms are included Reference track s oss Tune particle tracks will appear if one or more Reference particles are tracked The NTuple contains the usual track data The standard NTuple fields are X Y Z mm Px Py Pz MeV c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 The following additional fields are appended for format Extended format asciiExtended and format rootExtended Bx By Bz T
275. sh attempt to match a quad triplet into a solenoid This script is similar to triplet sh except it adds a solenoid after the quad triplet This is incomplete but demonstrates the gnuplot commands necessary to plot the profile emittance and beta of the beam 1 10 14 TJR G4beamline User s Guide 118 7 Tips and Techniques These generally useful tips and techniques have been found useful while using G4beamline to simulate several dozen different systems including suggestions from numerous users 7 1 Getting Help on Using G4beamline The primary means of obtaining assistance in using G4beamline is our user s forum http www muonsinc com tiki view_forum php forumId 1 You can also send email to mailto inquiries muonsinc com or to Tom Roberts the primary author of G4beamline mailto tjrob muonsinc com Some questions are more about Geant4 than G4beamline In particular detailed questions about physics processes and or physics lists are in this category For such questions you can use the previous paragraph but we will most likely redirect you to the Geant4 forums http hypernews slac stanford edu HyperNews geant4 cindex It s quite appropriate for users of G4beamline to join the Geant4 forums as well 7 2 Reporting Bugs in G4beamline The primary means of reporting bugs in G4beamline is our user s forum http www muonsinc com tiki view_forum php forumId 1 You can also send email to Tom Roberts the primary a
276. sired 1 10 14 TJR G4beamline User s Guide 72 for its color for invisible The special names plus minus and neutral will set colors for unnamed particles of each charge The name reference will apply to the reference track defaults to invisible kill particlefilter Will particlesourc particles from a list or force particles to decay A particlefilter will force the decay of certain particles when they enter the physical volume of the element The list of affected particles is in the decay argument and the normal Decay process is disabled for them In addition the kill argument is a list of particles to kill when they enter th element and the keep argument will kill all particles not named if it is not empty require is an expression invloving track parameters that will kill the track if it evaluates to zero use a comparison operator The variables available are X VY Z t Px Py Pz Ptot PDGid EventID TrackID ParentID Units are mm ns MeV c If nWait gt 1 particles will not be killed until they hit this element nwait times this can be used to limit the number of revolutions around a ring Decays are unaffected by nWait referenceWait does the same for the reference particle The element can be either a cylinder or a box set length and radius or set length and width and height Named Arguments cannot be changed in place cmd
277. srsseessesaes 129 7 19 Tunng Bending Masi ssi rinon ES E a E ANERE E OKE S ates 130 7 20 Setting the Phase of RF Cavities pillbox sessssessesessssessesssssressessessesseesessresseessesersseesseseess 132 7 21 Tuning the maxGradient of RF Cavities pillbox sssssessessssseessesseeseesseesesessseessesrrssresseses 132 T22 Mu ltipl Jobs in Parallel nnn ie hs ot eles otk aia a a a a aR a is 133 7 23 Performing a Scan of Values of Some Parameter scccsccssrcssssscssecsecsseccsssssaseseetesaces 134 7 24 Visually Scanning Events via the Command Line s ssssssessesnesseessessesresseesssrssseessesrrssresseses 134 7 25 Optimizing the Value of Some Patameter s 1 3 ncesio yee te uke egies 135 7 26 Using Two or More Reference Particles sa cc5 asseccusndeecnases aescaguisdandactnsdbtaasetwedsbneagepedacetecszeaceeas 136 7 27 Fitting to Plots and Histograms in HistORoot ccscccssccssscssrcesncsessscseccssccesecessasessscssacesnces 136 7 28 Interfacing to Other Programs vies sors cassia ce as aaa a EE Aad ot eee ania Aiea 137 7 29 EventID and TrackID and Encoding Information in them cceceeceesceesceeeteceteeeeeeeeaees 137 730 Ex mining Outer Events castes cote cose etu eect es E aaa cota aa oat 137 7 31 Increasing the Number of Events Displayed Visually cccccccccceseceseceeeeeneeesseceeeeeeeeensees 139 1 10 14 TJR G4beamline User s Guide 3 7 32 Building G4beamline Adding Your Own Code
278. straight line during a single step due to a magnetic field etc They are 1 10 14 TJR G4beamline User s Guide 31 Parameter Name Default Description deltaChord 3mm deltaIntersection 0 1 mm See the Geant4 Physics manual and User s Guide for a deltaOneStep 0 01 mm description and discussion epsMax 0 05 epsMin 2 5E 7 maxStep 100 mm The maximum physics step permitted to be taken Note this is a limit on the physics step integrating the equations of motion will take multiple integration steps within this Can be overridden in each element minStep 0 01 mm The minimum physics step permitted to be taken zTolerance 2mm How close to a specified Z position a step must occur the two steps surrounding the Z position are then linearly interpolated These parameters specify the trade off between tracking accuracy and CPU time These are reasonable values for beamlines or detectors of ordinary sizes with scales from roughly a few millimeters to a few tens of meters the length of a narrow beamline can reasonably extend to a few kilometers If you have objects smaller than a millimeter or so or are working on scales larger than a kilometer or so you should consider changing these values appropriately If you have small objects spread over a large volume in general you should select parameter values appropriate for the small objects and realize that the simulation will most likely require lo
279. sults are usually lost when a worker node runs out of memory or when the job exceeds its wall clock limit eno ee The following parameters control the MPI implementation MPI PackTracks Number of beam tracks per message default 100 MPI PackNTuples Number of NTuple rows per message default 1000 MPI IdleSleep Sleep time milliseconds of the sleep in a loop calling MPI_ Iprobe see below MPI _WorkerOutput Controls whether each worker writes to rank out 0 not Default 1 Rank 0 always writes to stdout and stderr worker nodes never do MPI Debug Controls MPI debugging output Default 0 In addition the parameter MPI_rank is set to the rank of the process as each rank processes the input file this can be used for debugging or distinguishing output files It is set to 1 if MPI was built but the run is in non MPI mode It is not set if MPI was not configured and built 1 10 14 TJR G4beamline User s Guide 153 Rank 0 writes to stdout and stderr in the usual way all other ranks have both stdout and stderr redirected to files rank out or closed if MPI WorkerOutput 0 G4Exceptions will be displayed on both rank out and stdout and the rank 0 process totals them over all ranks stdin is normally readable by rank 0 but that won t work as an input file because all ranks must read it Note that rank 0 only does management tasks and performs no tracking of beam On a Mac Pro with 4 cores it is appropriate to run
280. t files can also be converted Root 5 is quite powerful and can easily be scripted using C macros It is straightforward to open a root file select a TNtuple from it loop over its rows and write a new Root file and TNtuple or ASCII file in a new format The Root documentation and examples contain numerous macros of this sort If you have need for an interface that cannot easily be implemented you can suggest a new feature for G4beamline to implement it directly see section 7 3 7 29 EventID and TrackID and Encoding Information in them In G4beamline EventID is an integer between 2 and 2 147 483 647 Ox7FFFFFFF inclusive Note however that EventID s greater than 16777215 OXFFFFFF cannot be precisely represented in a float and their values in any NTuple will be rounded Values 2 and 1 are reserved for the Tune and Reference particles In G4beamline TrackID is an integer between 1 and 2 147 483 647 Ox7FFFFFFF inclusive Similarly TrackID s greater than 16777215 OXFFFFFF cannot be precisely represented in a float and their values in any NTuple will be rounded In addition the beam command will issue a warning for every primary TrackID greater or equal to the value of secondaryTrackID such a primary TrackID could be confused with a secondary s automatically generated TrackID Note there is no requirement that either EventID or TrackID be unique or sequential When G4beamline generates events the EventID s are assigned
281. t NTuple format see above for list filename Name of file minHit Minimum number of detectors hit default 0 perTrack Nonzero for an entry per track 0 for an entry per event default 0 union Set nonzero to perform a union of the detectors rather than combining them require Synonym for required minHits Synonym for minHit file Synonym for filename redirects stdout and stderr to a file output requires one argument the new output file Any output generated before this command will not appear in the file so this command should come at the start of the input file preceded only by setting parameters After the redirection it will re print the G4beamline version and the current parameter values to the file The most common usage is to redirect output to a file named like the root file when that is determined by parameter values param unset paraml 1 0 param2 3 0 param histofile Sparaml param2 output Shistofile out Defines parameter values Parameters are named strings used to parameterize the input file a few are used for program control Parameters are set by the param commend and on the command line all program arguments after the first are interpreted as name value param name value defines parameters If no arguments are present all parameters are displayed If the first argument is unset this command will not overwrite parameters that are already set e g from t
282. t converge Out of Memory Fatal Not enough memory Failed to achieve required Fatal The coil command could not achieve the required accuracy accuracy in constructing the field map given the limits on its size Material not found Fatal The named material does not exist Invalid Coordinate Type Fatal Invalid coordinate argument Invalid init during Event Internal coding error tracking Invalid start Fatal The start command is not valid Cannot determine Event The reference coordinates are not unique at the start of this reference coordinate track Probably means that radiusCut is omitted or too large segment in some corner or cornerarc command Coordinate Object Event Internal coding error Missing 1 10 14 TJR G4beamline User s Guide 199 Reference Coordinates Fatal Reference coordinates specified but no applicable reference not available particle was tracked Output File Exists Fatal To prevent confusion BLFieldMap will not overwrite an existing file Nesting gt 64 Fatal Groups can only be nested to 64 levels Object Already Exists Fatal The name of an object is not unique Already Initialized Fatal Internal coding error No Physics Registered Fatal No physics command in the input file No beam Registered Fatal No beam command or other beam G4VIS_USE not defined Fatal Attempt to use visualization but the program has no visualization compile
283. t handed usually with the Z direction in the nominal direction of the beam X is normally beam left and Y is normally up 2 4 1 Global Coordinates Global coordinates are merely the local coordinates of the World volume the outermost physical volume of the simulation which defines the entire world known to the program All beamline elements and physical objects of the simulation are contained within the world volume Note that the World volume automatically expands to hold any elements placed into it so the user need not be concerned with how large it is Any particle that reaches an edge of the World volume is killed right there Tracking is performed using global coordinates and electromagnetic fields are always determined using global coordinates but they are specified using the local coordinates of their element each placement of an element into the simulation includes the local gt global coordinate transformations needed 2 4 2 Local Coordinates There is a set of local coordinates for each and every element If the element has an associated field the field of the element is specified in local coordinates and the program automatically keeps track of the global local coordinate transforms required for each placement of the element including rotations for vector fields Whenever an element is placed inside a parent element e g a group or a box the parent s local coordinates are used in the place command except for the
284. t is both time consuming and error prone A better way is to use the probefield command with its input set to a file containing the global coordinates of the solenoid s center Just guess 1 10 14 TJR G4beamline User s Guide 129 a value for the current and run the simulation from the printed value you can take the appropriate ratio and quickly determine the current required to give the desired field You can also use the printfield command for this If instead you have a specified current for a given magnet then you will need the magnet s specifications to determine the field corresponding to that current Except for a solenoid without iron there is no simple way to relate field and current If you have a drawing of the magnet you could in principle construct a model of the magnet using an EM modeling tool Tosca Opera3D Ansys that is usually a major effort the drawing probably gives a value for the integral of B dl which should be enough for you to compute the field 7 19 Tuning Bending Magnets G4beamline is a realistic simulation program and like a real beamline the bending magnets in a simulated beamline must be tuned for position orientation and field current To model a real beamline that has the corners of the beam centerline marked on the floor a corner or cornerarc command will be used to model each corner This implies that the corners are fixed and the bending magnet must be positioned and tuned appropriatel
285. t the upstream edge of the group if this is the first element in the group The rename argument can be used to change the name of the element applies to traces and other uses of object names such as the NTuple name of a virtualdetector When placing into a group or other object the rename argument should normally begin with to include the parent s name otherwise multiple placements of the parent will generate multiple objects with identical names that should be avoided for output objects like G4beamline User s Guide 77 polycone 1 10 14 TJR virtualdetector Without a rename argument the parent s name is included automatically When multiple copies are placed z refers to the first and the rest are placed sequentially along z When placing an element into the World group Centerline coordinates are used unless coordinates global is present When centerline coordinates are used the parameter Zcl is set to the highest Z value used this is normally the Z value for the front of the next element when placed sequentially i e with no z value given Rotations The rotation parameter can be used to rotate this lement relative to the enclosing group The object is rotated not the axes Rotations are specified as a comma separated list of axes and angles in degrees rotate Z90 X45 rotates first by 90 degrees around Z and then by 45 degrees around X The axes are the loca
286. tcone the field from the macro particle there is a loop over all particles except the on currently being tracked This computation scales as N 2 where N is the number of macro particles that makes it computationally infeasible for more than a few hundred macro particles But for the particles used it is correct to within the following approximations a using macro particles interpolating between steps c omitting the L W potential The fields are computed using eq 63 8 9 Lifshitz Classical Theory of Fields i b linearly the radiation term in p 162 of Landau and gnoring the radiation term The computed fields are used in the usual Geant4 tracking Particle creation and destruction are handled properly This algorithm is primarily intended to test other space charge algorithms Named Arguments deltaT Time step ns radius Radius of macro particles mm charge Charge of macro particles times particle charge trackTwic O linear extrapolation l track 0 verbose Non zero for verbose prints 0 K Exponent for macro particle density 1 ignoreFieldWhenTracking For testing only 0 construct a sphere or section of one This is a direct interface to G4Sphere Named Arguments G4beamline User s Guide 87 start survey tess 1 10 14 TJR innerRadius The inside radius of the sphere mm
287. te cd G4beamline VERSION examples g4bl examplel g4bl viewer best To run the beam through the geometry execute g4bl examplel g4bl This will generate a Root file named g4beamline root To view it do historoot g4beamline root OTHER EXAMPLES There are other examples in the examples directory See README txt for details 1 10 14 TJR G4beamline User s Guide 179 Appendix 2 README Linux txt G4beamline on Linux Intel G4beamline 2 14 November 2012 TJR Note that the distributed 32 bit version of G4beamline for Linux was built on Scientific Linux Fermi 4 8 SLF 4 8 This is a derivative of RedHat Enterprise Linux 4 It should run as is on any RedHat derived Linux equal or later than that There is also a 64 bit distribution built on SLF 5 5 Before installing G4beamline you should first install openmotif should be available in your Linux distribution Some distributions install this automatically some don t It provides libXm so java http java sun com Select Java SE and all you need is the Java Runtime Environment JRE get the latest If you have installed the development kit JDK that includes the JRE Most distributions install this automatically You may need to install these x1l deprecated libs should be available in your Linux distribution but the name may be different Some distributions install this automatically some don t It provides libXp so compat libstdc i386 should be ava
288. the Tune particle track at z0 samples it again at zl and varies its tune variable in order to bring the expression to zero The tune variable is the first positional argument and can be used in the argument expression s for tunable arguments located after z0 Due to the simple solver between used there should be an approximately linear dependenc the tune variable and the expression This is suitable for tuning the By field of a genericbend or the maxGradient of a pillbox At each solver step the saved Tune particle is re started from z0 and when it reaches z1 the next step in the solver is taken Note that multiple tune commands can be used together as long as their z0 zl regions are properly nested by at least 0 5 mm i e each pair of regions must either not overlap at all or one must be wholly contained in the other This command can be complicated to use s the User s Guide for more description and examples Named Arguments z0 The starting z position in CL coordinates z1 The ending z position in CL coordinates initial Initial value of the variable name initialStep Initial step 0 to disable tuning step Synonym for initialStep start An expression that must be nonzero to start tuning default 1 expr The expression to tune to zero tolerance The tolerance for expr to be zero maxiter The maximum number of iterations 10 usertrackfilter Construct a usertrac
289. the detector can be included in an ntuple command including a pattern that matches its name in the detectors argument to the ntuple command Note that must match the name as placed i e includes rename not the name given to this command The noSingles argument may be useful in this case to avoid a huge NTuple of singles an empty NTuple may be created Note that secondary particles created within the detector will not get an entry until they have taken one step They ar guaranteed to do so For VisibleEdep this command knows the Birks constants for Scintillator POLYSTYRENE BGO and lAr For other materials you must supply a value or 0 0 will be used The NTuple fields are X VY Z mm Px Py Pz MeV c t ns PDGid ll e 13 mu 22 gamma 211 pit 2212 proton EventID may be inexact above 16 777 215 TrackID ParentID 0 gt primary particle Weight defaults to 1 0 Edep Energy deposited MeV VisibleEdep Energy deposited MeV reduced by Birks effect Ntracks tracks of this event that hit the detector T Valid formats root ascii no extended formats Named Arguments cannot be changed in place cmd radius The radius of the circular Detector mm innerRadius The inner radius of the circular Detector 0 mm solid height The height of the rectangular Detector mm width The width of the rectangular Detector mm length The l
290. the field maps rather than being absolute numbers yviewer 0 Openinventorxt on jlabi2 jlab org p File Etc Help Motion X Motion Y J e a Motion Z middleCryomodule To actually use the cryomodule lt z gt lt current gt lt Pout gt lt maxGradient gt 1 10 14 TJR G4beamline User s Guide 169 middleCryomodule S Zcryo9 399 SPo9 SVimax Other details such as virtual detectors cryostats and absorbers may be added easily as required In this example the polycone lay outside of the rfdevice however if tracking particles through the cavity far off axis were required the rfdevice could have been made larger and the polycone placed inside the rfdevice but outside of the timingVolume 1 10 14 TJR G4beamline User s Guide 170 9 File Formats Note that ASCII file formats begin with comments in column 1 that give both the field names and their units The historoot program is able to use these comments to give names to the fields of such files it ignores the units which are intended for humans 9 1 BLTrackFile generated by NTuple s read by beam The file format is ASCII Lines beginning with are comments First line is a structured comment if not present the input routine issues a warning BLTrackFile user comment Second line is a comment giving the column names x y z Px Py Pz t PDGid EvNum TrkId Parent weight Third line is a comment giving the units cm cm cm MeV
291. the minimum Chisquared will be a point focus Because of the front to back symmetry the two horizontal focusing quads have the same gradient Gminuit presents the user with a window containing sliders and edit boxes for the parameters plus buttons to execute the script once and to fit the parameters see the gminuit documentation for details X gminuit Script retums the value to minimize Script File tmp script 29776 W Param value Script writes the above plotfile V plot files and compute their Chi squared 100 0 i 0 0 0 0 0 0 0 0 15 1000 0 100 100 0 1 0 1 15 FitStep 0 0 0 0 0 0 5 NoLimit wv NoLimit v NoLimit v NoLimit w NoLimit w NoLimit w Limited w Limited w Limited wv Limited Limited Limited Fixed Fixed Fixed Fixed Fixed Fixed Fit The script run by gminuit computes the Chisquared to be minimized and also plots the profile of the beam as traditional 3 sigmaX is on top and 3 sigmaY is below the axis with the apertures of the quads plotted in green 1 10 14 TJR G4beamline User s Guide 117 v EES a 3 sigmax 100 3 sigmay 50 100 0 1000 2000 3000 4000 5000 6000 In practice a human user can find the best tune more quickly than the minuit minimization engine This is primarily because the human can watch the effect of parameter changes on the entire profile plot and use experience and knowledge that minuit does not have 6 13 emittancematch
292. the very rarely used case that timelncrement is set nonzero to study timing errors timeOffset is changed by that amount before the last pass without any further adjustments and the final fixTolerance test is disabled for the ATWORKING_ FINAL The state ATWORKING_ FINAL just tracks the particle though the rfdevice using the final timing and maxGradient this is important to ensure the next device sees the correct Tune particle The state is then changed to ATWORKING_ DONE If the state is ATWORKING_ DONE the routine always returns and does nothing The choice of timingMethod becomes important when particles are moving slowly For illustration compare the reference particle tracks through a single 201 25 MHz 744 mm cavity for 45 MeV c B 39 u and B 1 e with maxGradient 25 MV m and phaseAcc 90 RF using timingMethod maxE and atZ The e trajectories are virtually identical for both methods while the u trajectories display a distinct difference 1 10 14 TJR G4beamline User s Guide 165 45MeV c e mu 1 cell cavity method maxE atZ 45MeV c e mu 1 cell cavity method maxE atZ T T T T T T T T T T T T T T mu45MEVc maxE90 a txt reference u 3 18 mu45MEVc maxE90 a txt reference u 3 6 mu45MEVc atZ90 a txt reference u 3 18 mu45MEVc atZ90 a txt reference u 3 6 e45MEVc maxE90 a txt ref u 3 18 e45MEVc maxE90 a txt ref u 3 6 e45MEVc atZ90 a txt reference u 3 18 55 F e45MEVc atZ90 a txt reference u 3 6 Ez MV m Pz MeV
293. ticles but 100 000 is more sensible for all but the simplest physical Situations The bunch is created from the beam tracks before tracking begins There is one bunch for each reference particle Particles in the a G4beamline User s Guide 85 1 10 14 TJR bunch must be the same particle as the reference must initially be within dx dy dz of the reference particle and when boosted to the reference particle s rest frame must initially have beta lt maxBeta After boosting the particles to the beam frame they are placed into the grid pro rating to the eight nearest grid points The grid is dynamically re sized to keep the 99th percentile of the particles between 0 5 and 0 67 of the grid size This maintains a reasonable balance between resolution of grid points within the bunch and covering all of the particles Particles located at gt 85 of the grid size do not contribute to the field computation but are tracked using the field of the rest of the bunch and other bunches The grid has nx ny nz points there is a small computational advantage to using powers of 2 but any values gt 1 can be used For efficiency the convolution of the Green s function with the charge grid is performed using FFTs the grid is doubled in each dimension with the proper symmetry applied to the Green s function so the cyclical convolution of the FFTs gives the proper potential with infinite boundary conditions
294. tion in a GUI Environment Execution in a GUI environment such as Windows is similar to that in a command line environment discussed above The basic idea is to keep windows open so you don t constantly have to re configure them Usually when developing a new simulation or optimizing the parameters or configuration of a simulation one wants to see histograms or plots from each run before tweaking the input file and running another test run The idea is to run enough events to get statistically meaningful plots but to not take too long so one can iterate rapidly through choices For a simple system being simulated I can often perform the loop of edit simulate histogram choose new values in less than a minute per step I do this with four windows open simultaneously all in the same directory 1 The G4beamline GUI window 2 Optional The G4beamline User s Guide in a PDF viewer A PDF viewer makes it easier to scan the text for command names Can be omitted and the help text of W1 can be used instead 3 An editor window to edit the current input file 4 The historoot window It s best to use a monitor that is big enough to see all four windows at once but it works well if you can see all of one and parts of the others so you can rapidly switch windows with a mouse click The basic sequence is 1 W3 editor If it s not open already open input file in the editor and prepare the next version to try Use W2 help for hel
295. tor oases cchccwscccatoacu cat anss ex cetaiecdb cb alcane de bguvigeleane cage de waned ebavaeeds Soeensedanseoees 211 Tunng the Beamline se thio ate oks hat oa cae nd Drd tee tate hook Nal eo aun od Soa ha Pale eat Rl a Alaa Det 212 The Geant4 User Inter face ise gicte dct aeaereuadi cates apeeesledte ci guneeh tecalec a a deta es Ate ean 213 Event Time Limiter 553 5 xsaslaces asks Nechaaesscaetsevtdaaeasiacepiatahatioaneseastaabeaasielacaiae RANE TEE ERE 2NA Wall Clock Limitsessoren i ii is a e E TE E at AR AE ARAE 2 15 Event and Track Numbering EventID TrackID 0 cc ccecceccccesceesseeeseceeeeeeeeeaeecaeceeeneneensees DONG SOTO Ae feos tars a a ds ate tate ahs emic i ate aus dna A A E tata ah aes 3 Important Values that Affect the Validity and Accuracy of Simulations ceeceeeceseceeeneeeeeeeees S PSIG E ec aes sett cali aa maser seve Sc Vetistan geo aa galas Oo Se oot A T E A EA 3 2 Tracking Necoracy Parameters iniciis i n E ers eee E E RER 3 3 Electromagnetic Field Map Tolerance sssenneeseesseesseseesseessesessstessessrsstessessrsseessessessresseeseesressee 3 4 Secondary Creation Threshold in Physics Processes ccccsscessseeeteceseceeeeeeeeceseceeeeeeeenseeeaeens De eE E OE nae acca etn T E aN a th oa aR ae aan ae at eae 9 0 Fringe Fields Le e uassacees ws a ons one Wigs ve e Gas tee ven eek oo e oa eatin E Sf Stepping and Hard EdgESi meninius ietis ear ERA aae NEESER REE E AT ET E RERE 3 8 Radiative DecaysSeninen
296. toroot will write all selected EventID s to the file histo_events txt re writing it repeatedly as the slider is changed After selecting just the outlier entry its EventID will be the only entry in the file It is then straightforward to run G4beamline in visualization mode with the eventcuts command to select just those events listed in the histo_events txt file g4bl file in eventcuts file histo events txt viewer best The eventcuts command could be edited into file in instead of being placed on the command line in g4blgui the checkbox HistoRoot Events puts that eventcuts command into the command line The result is clear and obvious this simulation clearly needs shielding around the bending magnet Note this assumes the default treatment of pseudo random numbers the generator is seeded with the event before each event This won t work if you use the randomseed command to change that Note If your input beam is a file and that file has multiple tracks with the same event number G4beamline will treat each track as a separate event with that event number see the description of beams above That means that if an event selected via eventcuts has say three beam tracks only one of them need satisfy the conditions used to select the event The other two tracks with that event will be selected by eventcuts but may well look puzzling as they probably don t satisfy the conditions and will appear as separate tracks in
297. track and is simply sequentially assigned as tracks at different Z positions are written F 1 10 14 TJR G4beamline User s Guide 171 The region is REGION SIZE in Z from the first track of each region XP PP BFLD and EFLD should all be converted to a Centerline coordinates before calling write X This data format comes from ICOOL v 2 77 User s Guide section 4 2 3 The first line of the file is the title The second and third lines are comments supposedly units and column labels There follow the tracks one per line sorted by region The first track of each region should be the reference particle in ICOOL x parlance in g4beamline it is the reference particle if multiple reference particles intersect the region the first will be reference and the following ones will be considered beam K The variables for each track are X IEVT I event IPNUM I track for this event IPTYP I particle type gt 0 for positive charge i lt 0 for negative l e 2 mu 3 pi 4 K 5 proton IPFLG I flag always 0 JSRG I region number s above TP F time sec XP 3 F position meters PP 3 F momentum GeV c X BFLD 3 F Magnetic field Tesla EVIWT F weight EFLD 3 F Electric field V meter SARC F arclength meter set to 0 0 K POL 3 F spin set to 0 0
298. ts with the same name this is only a major problem for virtualdetector s and other output objects The group s name is included by default if no rename is used on the place command Named Arguments cannot be changed in place cmd length Overall group length along z mm width Overa group width mm height Overall group height mm radius Radius for a cylindrical group mm material Material of the volume outside children color Color of the volume of the group maxStep The maximum stepsize in the volume mm helicaldipole construct a helicaldipole magnet 1 10 14 TJR The field region is a cylinder with a helical dipole field plus a solenoid field The simple model 1 provides just a sine and cosine transverse dependence while the maxwellian model 2 has both dipole and quadrupole terms Both the dipole scale bD T and quadrupole scale bQ T m are now at rho 0 the user must G4beamline User s Guide 62 determine the correct values externally Note that this Element generates a magnetic field only and only within the cylinder defined by length and radius So it has no solid associated with it and is invisible Named Arguments radius The radius of the field region mm model The model of field calculated simple 1 rpj and ysd model 2 ttominaka et al model 3 modulations in bd bq bz 4 length The length of the field region mm bD T
299. ts for all but and possibly other parameters will be determined so that the erial largest error is less than toleranc center of the coil If mapFile is giv BLFieldMap format a field map in a binary format if any parameter changes it is times the valu fil of Bz at the is read in n th The cache file contains the parameters and is automatically regenerated Note that maxR and maxZ are by default determined to be large enough so that the field falls below tolerance large Named Arguments cannot be changed in place cmd this can be quote innerRadius Inside radius of the coil mm outerRadius Outside radius of the coil mm length Length of the coil along z mm material The material of the conductor default Cu tolerance The acceptable tolerance of the map nSheets Number of sheets used in the computation maxR Maxmum r value for the map automatically determined by default maxz Maxmum z value for the map automatically determined by default dR R interval between points of the map automatically determined by default dz Z interval between points of the map automatically determined by default filename Filename for cache deaults to name dat mapFile Filename for map e g from TOSCA exactComputation Set nonzero to use the exact computation without any field map 0 G4b
300. ts of CPU time Note that Geant4 tracking has two different meanings of the word step Physics step Defaults to a maximum of 100 mm and determines the maximum step for applying physics processes At each step it is set to the smallest value of o the current value of maxStep o the distance to the next geometrical boundary o the smallest value determined by any active physics process Integration step Determined automatically from the other tracking parameters primarily deltaChord and determines the accuracy of the integration of the equations of motion In a magnetic field this is of course a helix There can be many integration steps within a single physics step and usually are in a magnetic field In particular the accuracy of the tracking is usually not significantly improved for small physics step sizes For instance tracking 250 MeV c muons through 1 meter of liquid hydrogen in a 2 Tesla solenoid including multiple scattering and energy loss shows no significant difference between maxStep 1 and maxStep 1000 in position or momentum histograms the execution time differs by a factor of about 50 so don t set maxStep to a small value unless you have a specific reason to do so This comparison can only be done statistically not on an individual track basis because different values of maxStep inherently use different numbers of random numbers causing variations in stochastic processes like multiple scattering and ionization
301. tuneMomentum at a specified tuneZ position centerline coordinates This is most useful for a beamline with material that induces a significant energy loss in the reference particle such as muon cooling channels 2 The tune command can be used to tune any tunable argument to any set of elements This includes the By field argument of genericbend and idealsectorbend and the maxGradient argument of pillbox See the online help or section 5 for details about these commands Tests 29 32 verify the operation of these tunes and provide working examples To aid the user in fine tuning the beamline g4beamline implements the ability to track a Tune particle and a Reference particle before tracking the beam both are controlled by the reference command These particles are tracked with all stochastic processes disabled and nominally go right down the centerline of the beam The Tune particle is used to tune all desired beamline elements and the tuning process often forces it to be tracked multiple time through sections of the beamline after tuning is 1 10 14 TJR G4beamline User s Guide 27 completed then the Reference particle is tracked to give a clean readout of the reference trajectory and computation of the reference coordinates if used The Tune particle can be used to 1 Automatically set the timing of RF cavities so the Reference particle arrives at the desired RF phase 2 Automatically set the gradient of RF cavities so
302. ty and Accuracy of Simulations Particle simulations are inherently complicated and CPU intensive The Geant4 toolkit necessarily provides facilities to permit users to make trade offs between accuracy and CPU time G4beamline likewise considers this a user issue and provides interfaces to Geant4 mechanisms as well as some new capabilities To perform simulations that yield results you can trust you must make some choices that affect the accuracy and validity of the results It is often equally important to avoid becoming overwhelmed by useless information Features related to these are described in this section 3 1 Physics List The Geant4 toolkit contains a large number of physics processes that implement the transportation decays and interactions of particles In addition Geant4 is extensible and users can construct their own physics processes These processes are numerous and complex and often have complex relationships between different processes so it is a challenge for users to become sufficiently knowledgeable to select the necessary processes and implement them in code As a result the Geant4 collaboration has constructed a number of physics lists that are crafted from the library of physics processes to be suitable for a specific user domain G4beamline shields the user from much of this complexity and only offers to the user the choice among the Geant4 physics lists plus a few additional lists constructed for special purpose
303. ue at tmin is used if t timeOffset gt tmax the value at tmax is used Note that divide by zero is reported as invalid expression For a Li lens you probably want to use an expression like this if r lt 100 500 0 r 100 500 0 100 r where 100mm is the radius and 500T is the field at r 100mm Note that front 1 can be used to place this field Named Arguments cannot be changed in place cmd Tunable factorB Factor for the B field 1 0 factorE Factor for the E field 1 0 timeOffset Time offset ns Bx Expression for Bx Tesla use x y z By Expression for By Tesla use x y z Bz Expression for Bz Tesla use x y z or r z Br Expression for Br Tesla use r z Bphi Expression for Bphi Tesla use r z Ex Expression for Ex MV m use x y z Ey Expression for Ey MV m use x y z Ez Expression for Ez MV m use x y z or r z Er Expression for Er MV m use r z G4beamline User s Guide 57 fieldlines 1 10 14 TJR time Expression for time dependence factor use t nX Number of grid points in x ny Number of grid points in y nZ Number of grid points in z nR Number of grid points in r nT Number of grid points in t tolerance Required relative accuracy 0 001 length Length of field map mm width Width of rectangular field map mm height Height of rectangular field map mm r
304. und it with a thin tube with kill 7 10 How to Debug a Simulation An important debugging aid is the geometry test performed by G4beamline The results appear in the output just before tracking In the real world two objects cannot occupy the same space the simulated world does not have this restriction and input file errors can generate unphysical and invalid overlaps The Geant4 optimization of tracking requires a strict hierarchical arrangement of volumes Usually any geometry errors listed should be corrected in your input file before believing the simulation results in some cases this is difficult or impossible and some exceptions are listed in section 8 2 on Advanced Topics The most common debugging technique is to add steppingVerbose 1 to the command line or the Parameters field of the GUI This causes G4beamline to print to stdout the track variables at every step That usually lets you figure out what is going wrong Note that by setting steppingFormat you can control what track variables are printed see the help for details this can be very useful when debugging E and B fields or spinTracking In most cases it is best to widen your display s window before running so lines are not wrapped 140 columns is usually sufficient Sometimes the problems are subtle and only rare events look crazy If you can select those crazy events with sliders in historoot then you can set its EventID field to cause it to write the h
305. uration of a simulation one wants to see histograms or plots from each run before tweaking the input file and running another test run The idea is to run enough events to get statistically meaningful plots but to not take too long so one can iterate rapidly through choices For a simple system being simulated I can often perform the loop of edit simulate histogram choose new values in less than a minute per step I do this with four windows open simultaneously all running bash in the same directory W1 A command line window in which I run G4beamline simulations W2 A command line window in which I run g4b and to which I type help command whenever I need help on a command or its arguments W3 A command line window in which I edit my current input file I happen to use vi but you should use the editor you are most familiar with W4 A command line window in which I run historoot This can be window 1 if historoot is put in the background It s best to use a monitor that is big enough to see all four windows at once but it works well if you can see all of one and parts of the others so you can rapidly switch windows with a mouse click The basic sequence is 1 W3 editor If it s not open already open input file in the editor and prepare the next version to try Use W2 help for help if necessary When finished save the file to disk without exiting the editor 2 W1 command prompt run g4b input file and
306. us of your desktop manager To use the command line programs you must add the G4beamline programs into your PATH source g4beamline VERSION Linux bin g4bl setup sh You may put this into your HOME bash_ profile There is a similar g4b setup csh The first time you run G4beamline it will launch a helper program G4bIData to download the required Geant4 data files 1 1 1 3 Mac OS X Intel Prerequisites e Java SE Runtime Environment 1 5 or later http java sun com if you have the JDK installed that includes the runtime environment Java is normally installed on Mac OS X e Root 1 24 or later http root cern ch Root is not required if you will use only ASCII output files though you probably will find the HistoRoot program useful to generate plots of Root and ASCII files and it requires a specific version of Root The distribution file is G4beamline VERSION dmg available from http g4beamline muonsinc com Simply download it open it and drag the G4beamline icon to your Applications folder Drag the G4beamlineDocumentation and G4beamlineExamples folders to your desktop if desired Then eject the installer disk image and move the downloaded file to the trash As usual you can then drag the application icon from Applications to the Dock 1 10 14 TJR G4beamline User s Guide 7 If you want to use the command line programs you must add the G4beamline programs into your PATH source Applications G4beaml
307. uthor of G4beamline mailto tjrob muonsinc com 7 3 Requesting New Features in G4beamline The primary means of requesting new features in G4beamline is our user s forum http www muonsinc com tiki view_forum php forumId 1 You can also send email to Tom Roberts the primary author of G4beamline mailto tjrob muonsinc com 7 4 Getting Help on Individual G4beamline Commands The source code of each G4beamline command includes help text for the command and its individual arguments it is printed by the he p command This text is the primary source of information about the command and is copied into this User s Guide and into the help text of the G4beamline GUI You can obtain help on each command in several ways 1 From a command line type g4b on one line and then help command on a new line in response to the cmd prompt 2 Run the G4beamline GUI and if the help text is not displayed push the He p button You can then scroll around and find the desired command 3 Look in section 5 of this document Note that the definitive source is number 1 so if there is a question about changes e g in different versions of G4beamline that is the method to use In particular the help text in the GUI and in this document can get out of date 1 10 14 TJR G4beamline User s Guide 119 7 5 In what Directory should Work In general it is a poor idea to put your simulations inside the G4beamline install directory
308. value background Color of the background setup value row Initiates a new row of plots height The relative height of this row The first row has a height of 1 0 which sets the scale space none Displays like a plot but is empty title Title of the pad 1 10 14 TJR G4beamline User s Guide 149 textHeight Height of text in pixels setup value background Color of the background setup value time none Displays like a plot but contains the current time in ns title Title of the pad textHeight Height of text in pixels setup value background Color of the background setup value Position none Displays like a plot but contains the current Z position of the reference particle mm title Title of the pad textHeight Height of text in pixels setup value background Color of the background setup value Within a row all plots share equally the total width of the window The rows are laid out to use the entire height of the window but the fraction of each row is determined by its height totalHeight totalHeight is the sum of height for all rows There can be a different number of plots in each row You can use windowWidth windowHeight the row height s and the number of panes per row to have both large and small panes in one movie Usually each pane should be approximately square To play with the layout it is helpful to temporaril
309. ve defaults for ease in testing param unset first 0 last 1000 use Sfirst for the Root file root will be appended param histoFile first output ShistoFile out beam Gaussian firstEvent S first lastEvent Slast Any other output files e g format ascii for virtualdetector zntuple timentuple etc should be set to first as well so multiple instances of the program won t overwrite output files The simulation is run like this on a 4 CPU system bash shell g4bl input file first 0 last 999999 amp g4bl input file first 1000000 last 1999999 amp g4bl input file first 2000000 last 2999999 amp g4bl input file first 3000000 last 3999999 amp tail f O out watches the output from the first instance Or tail 1 out gives a snapshot of where each instance is The output files will be 0 root 1000000 root 2000000 root and 3000000 root The historoot program can be used to generate histograms historoot root You can select the 4 instances of a given NTuple and historoot will generate histograms and plots containing results from all 4 million events The example MICE _StageVI g4bl is a real world example using this technique 8 1 2 Using the gminuit Program to Tune Values The gminuit program http www muonsinc com ComputerPrograms Gminuit was specifically designed to permit the easy tuning of values in an input file for G4beamline Because any argument to any G4beamline command can be set from a
310. ven in section 5 of this document and in the output from help commandname 2 3 Geometry As in Geant4 geometry in G4beamline is specified at the element level and in the placement of elements Each element has an inherent shape and size which are usually parameterized that determine the basic geometry of the element in isolation Elements can be placed into the simulated World or into other elements placed into the world with specified geometrical relationships consisting of both rotations and offsets relative to the parent s coordinates This will become obvious when you look at the various element definition commands e g the box and tubs commands and the place command Because of the way Geant4 does tracking there are restrictions on the geometrical intersections of elements e Every daughter element must be wholly contained in its parent e No sibling elements can intersect each other in any way This results in a strict hierarchical arrangement of element volumes with the World volume as the root and outermost volume from which all other volumes are descended The World volume and the group element will automatically expand to the size required to hold all daughter elements placed into them G4beamline has a geometry test that will verify these requirements for points distributed on the surfaces of every element Due to round off in tracking the geometrical intersections have a default accuracy of 10 microns the geomet
311. visualization or tracking Also determines the visualization driver to use See section 2 8 above stepping Verbose 0 When nonzero causes each step to be printed to stdout steppingFormat see below The format of lines printed by steppingVerbose histoFile g4beamline root The histogram output filename histoUpdate 0 When nonzero causes G4beamline to update the histoFile after each block of this many events have been tracked worldMaterial Vacuum The material of the World volume Zcl Initially 0 the place command sets Zc to the downstream Z position of the placed element when using Centerline coordinates not for Global coordinates or placements into elements other than the World The user can set Zc but that has no effect on the place command eventTimeLimit 30 CPU Time limit on each event sec fieldVoxels 200 200 200 Size of voxels for field computation mm mm mm maxStep 100 Maximum physics step size global Each element can have its own value for maxStep 1 10 14 TJR G4beamline User s Guide 39 l wallClockLimit Limit on wall clock time for the entire job seconds lt 0 means infinite There are also parameters that control the values of Geant4 tracking parameters discussed in section 3 2 The steppingFormat parameter controls how the steppingVerbose printing is performed It is a sequence of names of track attributes separated by commas
312. wait for it to finish If there was an error go back to step 1 1 10 14 TJR G4beamline User s Guide 120 3 W4 historoot do File OpenFile and open g4beamline root or whatever file the simulation wrote Select the desired NTuple and set the expressions to plot if necessary the plot configuration will remain from the previous iteration and then push CreatePlot 4 W4 historoot do File CloseAllFiles This is important to avoid confusion On Windows this is essential because if historoot has the Root file open g4beamline won t be able to write to it and the next step 2 will fail for that reason 5 Examine the plot and determine what to do next Go back to step 1 By using separate command line windows the command line history in each will permit you to avoid re typing commands reducing typos and speeding things up considerably By keeping historoot and the editor open you avoid the delay of re configuring them each time When constructing a new geometry plots are usually not needed and the GUI is better suited to viewing the system easily So in window 1 I type g4blgui input file and push its Run button instead of running g4b directly with the best viewer selected W4 historoot is not used I find that the GUI is easier to use than the command line when using visualization though it works fine to type g4b input file viewer best and then run beamOn 10 to the Geant4 Idle gt prompt 7 8 Basic Execu
313. way to obtain a list of all its commands control manual This command can use either method above The most common reason to issue a Geant4 command is to set some verbose level for debugging or investigating some aspect of Geant4 most especially its physics processes G4beamline sets all verbose levels to 0 initially Here is the list of commands that G4beamline runs to do that control verbose 0 run verbose 0 event verbose 0 tracking verbose 0 hits verbose 0 material verbose 0 process setVerbose 0 all process verbose 0 process eLoss verbose 0 Another reason to use a Geant4 command is to control a viewer Use g4ui when 4 for that The selected viewer s initialization commands from viewer def will be executed before such commands 7 12 Obtaining Plots and Histograms There are a number of different ways to generate plots and histograms from G4beamline output files I generally find HistoRoot to be most convenient but each user should use the method they are most comfortable with Both HistoRoot and PAW can fit functions to histograms or plots excel and some other spreadsheets can do so perhaps with more overhead 1 10 14 TJR G4beamline User s Guide 124 General Remarks In most cases you must cut on PDGid when generating a plot or histogram PDGid is the Particle Data Group s ID for the particle of a track so this is selecting the type of particle to plot G4beamline simulations are realistic and pa
314. when a viewer is selected 7 25 Optimizing the Value of Some Parameter s When designing a new machine or facility there is frequently the need to optimize some parameters The program gminuit is available for this and interfaces well to G4beamline and to other programs Download it from http muonsinc com in the Computer Programs link at the left The basic idea is to write the input file to have command line parameters for the parameters to be optimized and to configure gminuit to vary them A shell script must be written to run G4beamline and then compute a Chi squared for gminuit to minimize See the gminuit documentation for details how to do this Gminuit will optimize any quantity that can be computed in a shell script and is not limited to G4beamline In practice one finds that program overheads are rather large so there is a big advantage to requiring fewer iterations A human can often converge on an optimum faster fewer iterations than can gminuit s minimizer This is especially true if the shell script can present a useful graph to the user rather than just a single value of the Chi squared Note also that minimizing an integer valued expression such as the of particles transported to a given location is difficult in gminuit one should set the granularity of MINUIT to 1 0 or more and run enough particles so that the statistics are reasonably good at least 1 000 particles and 10 000 is better The examples director
315. when placing elements into the World volume bending magnets must normally be placed into the World volume not into a group or other parent volume NOTE the transform from global to centerline coordinates must be performed at the start of tracking each particle This transform can be ambiguous in certain regions near corners see the figure at left in which the heavy black line is the centerline with 2 corners and 3 segments the blue and green ambiguities are minor because they involve adjacent regions but the red one is serious because it involves non adjacent segments a ring can be much worse The yellow regions appear to belong to no segment and are simply assigned to the next downstream segment The tracking of particles handles the change of centerline segments naturally moving from segment to segment in order but any jump or start must deal with the ambiguities e g the initial point of beam particles or secondaries The solution is to specify a radiusCut for every start corner and cornerarc command this is a limit on a particle s radial distance from the centerline indicated by the dashed lines in the figure This removes the serious 1 10 14 TJR G4beamline User s Guide 14 ambiguities and the remaining minor ones are resolved by using the earliest region of the centerline for which the global coordinate point is inside the radiusCut Most beamlines have apertures that can be used to determine an appropriate radiusCut
316. where it first entered the rfdevice and the repeat the process Often multiple Tune Event 2 particles or passes are used to setup the RF device The routine s only points of interest are the entrance and exit of the timingVolume The routine is a state machine associated with a single RF device described by rfdevice the state is set before returning to G4beamline UserSteppingAction goes through a number of states Initially upon first entering the rfdevice s timingVolume it is in the ATWORKING UNKNOWN state if sufficient information exists to completely define the system i e timeOffset and maxGradient both set explicitly the state is set to ATWORKING DONE Otherwise if timeOffset is set explicitly the state is set to ATWORKING BYPASS and if not it is set to ATWORKING_ OFFSET If no maxGradient is specified it is set to an estimated reasonable working value Upon entering the rfdevice s timingVolume various initializations are done a snapshot is taken of particle and the track is saved at that point Control is returned to G4beamline and the particle continues with UserSteppingAction called each step but it does nothing until the particle exits the timingVolume Then another snapshot is taken various calculations are done the conditions and 1 10 14 TJR G4beamline User s Guide 162 state changed and the track returned to the spot just inside the entrance of the timingVolume via the saved track Generally only one Tune pa
317. with cuts applied based on expressions there are four sliders which implement cuts that affect the plot in real time For more complicated analyses e g computing masses of multi particle states Root can be used as an analysis platform this is advanced usage and is beyond the scope of this tip Gnuplot Gnuplot can directly read the ASCII NTuples written by G4beamline add format ascii to the command Note that Gnuplot does not generate histograms you ll have to use another program to do that Gnuplot is especially good at displaying multiple trajectories from trace format ascii oneNtuple 1 gnuplot is available for Linux as part of the distribution for Mac OS via Fink and for Windows via http www gnuplot info Excel and other Spreadsheet Programs Excel and most other spreadsheet programs can read the ASCII NTuples written by G4beamline add format ascii to the command Each line is a row of the NTuple with tabs separating the columns the first 2 3 lines give comments column names and column units optional PAW PAW can read the ASCII NTuples written by G4beamline add format ascii to the command possibly after a format conversion 7 13 Obtaining Pictures of the System and Events G4beamline is a complicated and flexible program and like all such programs it is subject to garbage in garbage out So it is important to check and verify that your input file actually represents the 1 10 14 TJR G4beamline
318. world volume When placing an element into the World volume you can specify either Centerline coordinates the default or global coordinates the local coordinates of the parent here the World volume 2 4 3 Centerline Coordinates Centerline coordinates are intended to represent the nominal centerline of a beamline with the Z axis running down the center of the beamline the X axis is beam left and the Y axis is up This includes corners generated by bending magnets The centerline coordinates are initially identical to the global 1 10 14 TJR G4beamline User s Guide 13 coordinates but the start corner and cornerarc commands will change that each bending magnet is normally immediately followed by a matching corner or cornerarc command By default elements placed into the World volume use centerline coordinates to specify the placement but global coordinates can be used if desired Centerline coordinates apply only to the World volume They are piecewise linear and inside bending magnets they will differ from the theoretical reference orbit coordinates commonly used in accelerator physics the cornerarc command will approximate reference orbit coordinates by using three corners chosen to have the same length along Z as the reference orbit coordinates have along the arc Note that the corner and cornerarc commands cannot have an angle greater than 90 if necessary this limit can be worked around by using two cornerarc s in a row with ha
319. x cluster or other multi system you will need to learn how to submit multiple batch jobs 2 The ability to assign a unique range of event numbers to each job Do this with parameters in your input file I use first and last and the commands are param unset first 1 last 1000 beam firstEvent first lastEvent last 3 The ability to assign a unique Root output file to each job Use first in the name of histoFile param histoFile first 4 The ability to combine all of the Root output files into histograms and plots Use HistoRoot to read all the root files and simply select the same NTuple from each file HistoRoot will combine all selected NTuples into each plot Note that this works well up to perhaps 32 parallel jobs above that it becomes quite cumbersome 1 10 14 TJR G4beamline User s Guide 133 7 22 2 Via the Message Passing Interface MPI On systems that implement MPI it can be used to speed up a simulation by a factor that is almost the number of CPUs available The advantage is that all outputs from the different instances are combined into a single output typically one Root file one stderr and one stdout See section 8 5 The program scales well up to at least 24 CPUs and often more depends in detail on the system being simulated and on the computer hardware used more complex systems will scale efficiently to more CPUs The basic command is mpirun np 5 g4bl input file parameters This will run 5 inst
320. xorg x1ll libs xorg x1ll libs xorg x1ll libs xorg xll libs libstdc i386 glibc i686 libgec i386 glibc i686 xorg xll libs xorg xll deprecated libs i386 1 10 14 TJR 1386 1386 1386 1386 1386 1386 1386 1386 1386 lib tls libpthread so 0 lib libdl so 2 usr X11R6 lib 1ibGLU so 1 usr X11R6 lib 1libGL so 1 usr X11R6 lib libxXm so 3 usr X11R6 lib libXpm so 4 usr X11R6 lib libXmu so 6 usr X11R6 lib 1libxXt so 6 usr X11R6 lib libxXext so 6 usr X11R6 lib 1ibxX11 so0 6 usr X11R6 lib 1libXi so 6 usr X11R6 lib 1ibSM so 6 usr X11R6 lib libICE so 6 usr lib libstdct so 6 lib tls libm so 6 lib libgcc_s so 1 lib tls libc so 6 usr X11R6 lib libxXxf86vm so 1 usr X11R6 lib libxXp so 6 G4beamline User s Guide 182 Appendix 3 README Windows txt G4beamline on Windows XP Windows Vista and Windows 7 G4beamline 2 14 November 2012 TJR Before installing G4beamline you must first install Java http java sun com Select Java SE and all you need is the Java Runtime Environment JRE get the latest If you have installed the development kit JDK that includes the JRE You may want to install Root http root cern ch or http historoot muonsinc com You may install any version of Root because G4beamline is built with its own instance of Root and is independent of whichever Root you install If you want to use HistoRoot however you should install the version of Root from http histo
321. y The standard criterion is that a reference particle coming into the magnet along the centerline of the beam should exit the magnet along the centerline both measured outside the fringe fields of the magnet If there are solenoids or other magnets near the bending magnet such that their fringe fields overlap then the tuning of the bending magnet may depend on their settings Note that if quadrupoles are used to steer the beam these remarks apply to them too See also section 2 11 Tuning the Beamline To begin make sure you have a reference command that puts a reference particle down the centerline into the bending magnet This implies that if you have multiple bends in your beamline you should start tuning with the first bend and proceed downstream The usual orientation for a rectangular bending magnet is with its front and rear faces angled at half the total bending angle to the centerlines It must be placed a short distance behind the corner in order that its fringe fields are accounted for and must be placed a bit to the outside of the bend so the two centerlines are equidistant from the left and right sides of the aperture The usual orientation for a sector bending magnet is with its front and rear faces perpendicular to their centerlines Other orientations are possible and can be used to affect the vertical focusing of the bending magnet The beamline designer will specify the appropriate angle of the magnet relative to the cent
322. y but usually there are Following the time command are lines containing 2 or 3 doubles t BE where t is the time nanoseconds and B and E are factors for the fields If E is omitted the value for B is used These values will be interpolated in time with a cubic spline that can handle either uniform or non uniform spacing of points along t The time command can com ither before or after the cylinder or grid commands but not within either of their sequences Note a cubic spline is used to interpolate between points and that can cause over under shoot near an abrupt change Combined with period this gives an excellent representation of sinewave cosinewave Note that time dependence can currently only be specified via the time command in an input file i e not programmable method exists Example block input file this is an examp BLFieldMap input file suitable for a solenoid grid interval is 1 cm The region of validity is 390 lt Z lt 390 and 0 lt R lt 90 param normB 1 0 current 1 0 cylinder Z0 0 0 nR 10 nZ 40 dR 10 0 dZz 10 0 extendZ flip Br Bz 40 lines of 10 values Z 0 thru 2 390 Br 40 lines of 10 values Z 0 thru Z 390 EOF Example pointwise input file this is an example BLFieldMap input file suitable for a solenoid 1 10 14 TJR G4beamline User s Guide 174 cy e E F FF F g
323. y default extending the field in a rectangle extending the straight aperture along the local z This is first order only and assumes the magnet is infinitely wide the fringe field extends outside of the magnet aperture only in a region extending the aperture in x and y As the fringe field is first order only it is slightly non Maxwellian It is calculated using Enge functions Note that there is no field inside the iron this can result in gross tracking errors for particles in the iron and implies that kill 1 is desirable By default the aperture is filled with a box volume of the fieldMaterial this prevents placing any object inside the aperture With openAperture 1 no aperture volume is used and objects can be placed into the parent volume that are inside the aperture Named Arguments cannot be changed in place cmd Tunable fieldWidth The width of the field region mm fieldHeight The height of the field region mm fieldLength The length of the field region mm ironWidth The width of the iron region mm G4beamline User s Guide 60 ironHeight ironLength By maxStep fie fie ldMaterial ldColor ironMaterial ironColor kil fringe fringeFactor openApertur The he The le The ma The ma The ma The co The ma The co Set no Fringe comma Fringe Set no ight of the iron region mm ngth of the iron region mm gnetic field
324. y of the G4beamline distribution contains triplet sh which tunes a quad triplet to achieve a focus at z 6000 Note that it presents the user with a plot of the beam s horizontal and vertical sizes as a function of z along the beamline this additional information permits a human to find a solution much faster than the minimizer the locations of the horizontal and vertical zero crossings tell you which way to change the quads values Even so using gminuit in manual mode is significantly easier than it would be to do this by manually typing each command gminuit presents the user with a simple way to change the values of the variables and to execute the program once 1 10 14 TJR G4beamline User s Guide 135 7 26 Using Two or More Reference Particles Unlike most accelerator programs G4beamline realistically handles particle decays and interactions This makes it suitable to simulate muon beams from a primary proton beam all the way to a muon experiment or cooling channel This means that the portion of the beamline just after the production target should be optimized for pions and the portion at the end should be optimized for muons The best way to do this is to use two reference particles one starting at the production target with particle pit and one starting at a suitable downstream point with particle mu The key point is that no tuning should be done in the region where both reference particles are tracked In exampleAUGOS in the pio
325. y set tMax and duration to small values to speed up the production until the layout is what you want Many simulations start at t 0 and for them it is best to set tMin to a small value e g 0 001 so the initial tracks show up in the viewer when the file is opened but not playing Here is the examples Movie in file that generated the examplel movie referenced above Movie from examplel in with movie command outputs a FI setup outputFile examplel swf tMin 0 001 tMax 18 duration 1 e t red mut blue others gray neutrinos particle 11 FFO000 13 0000FF 0 808080 plot filename g4beamline root xMin 800 xMax 800 yMin 800 yMax 800 x x y y plot xMin 50 xMax 50 yMin 50 yMax 50 x Px y Py row plot xMin 800 xMax 800 yMin 50 yMax 50 x x y Px plot xMin 800 xMax 800 yMin 50 yMax 50 x y y Py lash row height 0 1 time Here are the commands used to generate and display that movie cd g4beamline 1 16 Darwin gt examples g4bl examplel in movie g4blmovie movie in open examplel swf 1 10 14 TJR G4beamline User s Guide 150 8 4 User Code for the usertrackfilter Command The usertrackfilter command requires that the user compile code for use with G4beamline The usertrackfilter element permits the user to supply code that applies to every track that enters the physical volume of the element this code can e Kill tracks based on arbitrary criteria e Modify the momentum time and o
326. y the only part of G4beamline that causes problems for users getting it to work on their systems In general on Linux and Mac OS X a working X windows display is required this means on Linux you usually will run one of the common desktops KDE or Gnome and use a terminal window to execute the G4beamline program On Mac OS X you may need to run the X11 application and either run g4b from an xterm or specify the DISPLAY manually since Leopard the X11 application gets run automatically when a connection to the X Windows display is made G4beamline visualization requires that both the Motif and the OpenGL extensions be configured on the display This means that both the X windows client the G4beamline program and the X windows display server the display keyboard mouse need them installed If you run G4beamline on your desktop Linux system this usually happens naturally but if you connect from your desktop to a Linux server and run G4beamline there then you must make sure these extensions are installed on both systems In particular if you use the Exceed program on a Windows desktop to connect to a Linux server be sure to install Exceed s OpenGL extension This also applies to Mac users G4beamline is an X windows application not a native Mac application On Windows all necessary graphics extensions should be installed by default Remote displays e g via Citrix should work as usual If you run g4bl with a viewer parameter and it cras
327. ycle to 25 MV m and placing a positive particle on crest rfdevice rfl maxStep l1 maxGradient 25 phaseAcc 90 1 10 14 TJR G4beamline User s Guide 166 A typical case where a positive particle will see some synchrotron motion later particles see more acceleration 20 before crest rfdevice telsa9cell maxStep 1 timingMethod maxE phaseAcc 70 maxGradient 40 while to get the same synchrotron motion for a negative particle rfdevice tesla9cell maxStep 1 timingMethod maxE phaseAcc 250 maxGradient 40 To specify the 8 before negative crest for e but request that the output momentum be set to 3 GeV c rfdevice cebaf7cell maxStep 1 timingMethod maxE phaseAcc 262 0 fixMomentum 3000 Success ensures that the found maxGradient satisfies both AtimeOffset lt timingTolerance and P fixMomentum lt fixTolerance Building a Cryomodule Complicated assemblies may be constructed in G4beamline using groups and macros Since various quantities often must be often passed to internal components macros are used here to construct a cryomodule A rfdevice need not have material walls it may serve as merely a place to put a known RF field map This example rfdevice has no physical components but does have a field and a timingVolume rfdevice RF2 innerLength Ldoublecell iris2iris cl frequency freqGHz fieldMapFile RF2_ 1MV_ wot BLfmt innerRadius SinnerPipe S cl pipeThick 0 wallThick 0 irisRadius SinnerP
328. yles StillDrawStyle wireframe Now rotate the image using the mouse until you can see the white reference track inside the bending magnet ignore the beam track s that are other colors zoom in if necessary and use a ruler or judge by eye whether or not it is centered left right If it is not centered guess how much change in Xoffset is needed Then go back to tuning Zoffset with this new value no viewer Once you have values for Zoffset and Xoffset edit the input file and put them in If you want to handle beams with different momenta you can parameterize the momentum and B1 Field like this assuming you initially tuned at 200 MeV c and B1Field for 200 MeV c was 2 10525 Tesla param unset MOMENTUM 200 beam Gaussian meanMomentum SMOMENTUM reference referenceMomentum SMOMENTUM tune BlField initial 2 10525 SMOMENTUM 200 1 10 14 TJR G4beamline User s Guide 131 7 20 Setting the Phase of RF Cavities pillbox The phase of an RF cavity pillbox is determined by its timeOffset and timeIncrement arguments If timeOffset is not specified it is automatically set to phaseAcc by the Tune particle The basic method used to set the phase when the Tune particle enters the volume of the pillbox its track parameters are saved and an initial value of timeOffset is estimated based on its current velocity and the distance to the center of the cavity Then it is tracked to the center of the cavity and its phase is checked the volu
329. zable SampleMovie g4bl Examplel g4bl with a movie command added Us movi Movie in in with g4blmovie An input file for g4blmovie works with SampleMovie g4bl 1 10 14 TJR G4beamline User s Guide 101 triplet sh A script to tune a quad triplet for point to point or parallel to point focusing emittancematch sh A script that demonstrated emittance matching Uses gminuit Uses gminuit tclsh wish and gnuplot tclsh wish and gnuplot Magnets and Windows Magnet field maps and window profiles for MICE StageVI g4bl 6 1 Example1 Simple Tracking and Virtualdetectors F QGSP is the but QGSP_BI physics QGSP B the beam is Examplel g4bl simple first example Simpl xampl g4beamline input file a 200 MeV mu Gaussian beam is tracked through l1 meter drift spaces into four detectors default physics use case for High Energy Physics ERT is better for low energy simulations ERT nominally headed in the Z direction beam gaussian particle mut nEvents 1000 beamZ 0 0 sigmaX 10 0 sigmaY 10 0 sigmaXp 0 100 sigmaYp 0 100 meanMomentum 200 0 sigmaP 4 0 meanT 0 0 sigmaT 0 0 a reference particle reference particl mu referenceMomentum 200 BeamVis just shows where the beam comes from box BeamVis wid place BeamVis z 0 th 100 0 height 100 0 length 0 1 material Vacuum color 1 0 0 define the detector

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