BDSIM User`s Manual v0.4
Contents
1. 3 3 9 octupole octupole defines an octupole Attributes 1 length m default 0 k3 normal octupole coefficient k3 1 B rho d B dz m Positive k3 means horisontal focusing of positively charged particles default 0 ks3 skew octupole coefficient ks3 1 B rho d B dz m where x y is now a coordinate system rotated by 30 degrees around s with respect to the normal one default 0 tilt roll angle rad about the longitudinal axis clockwise outR external radius m of magnet default set to aper 1cm Chapter 3 Lattice description 8 Example of octupole 1 0 5 m k3 0 5 tilt 0 01 3 3 10 multipole multipole defines a multipole Attributes e 1 length m default 0 e knl normal multipole knl n 1 B rho d B dz m e ksl skew multipole ksl n 1 B rho d B dz m where x y is now a co ordinate system rotated by 30 degrees around s with respect to the normal one default 0 e tilt roll angle rad about the longitudinal axis clockwise e outR external radius m of magnet default set to aper lcm Example mul multipole 1 0 5 m knl 0 0 1 ksl 0 0 0 3 3 11 rf rf defines an rf cavity Attributes e 1 length m default 0 e gradient field gradient MV m Example rfi rf l 5 m gradient 10 MV m 3 3 12 rcol rcol defines a rectangular collimator The longitudinal collimator structure is not take2. page 17 3 4 2 beam The parameters related to the beam are given by the beam command beam lt name gt value The available parameters are e particle particle name e e gamma proton etc e energy particle energy e distrType type of distribution e distrFile input bunch file Example beam particle et energy 100 MeV distrType gauss For more details see Appendix C Bunch description formats page 28 3 4 3 sample To record the tracking results one uses the sample sample range lt element gt The sampling plane is then inserted before lt element gt Example sample range d Cylindrical sampler of length 1 is put around element lt element gt at distance lt r gt with the command sample range lt element gt r r0 1 10 3 4 4 use use command selects the beam line for study use period 11 range q1 q2 Chapter 4 Visualization 16 4 Visualization When BDSIM is invoked in interactive mode the run is controlled by the Geant4 shell A visualization macro should be then provided A simple visualization macro is listed below Invoke the OGLSX driver Create a scene handler and a viewer for the OGLSX driver vis open OGLIX Create an empty scene vis scene create Add detector geometry to the current scene vis scene add volume Attach the current scene handler to the current scene omittable vis sceneHandler attach Add trajectories to the current sce
3. distrFile bunches beam dat The following distribution types can also be generated e Gaussian beam distrType gauss sigmaX sigmaXp sigmaY sigmaYp sigmaE Elliptic shell a thin elliptic shell in x x and y y with given semiaxes beam distrType eshell x xp y yp CU de CO N Ring beam distrType ring X0 YO Rmin Rmax sigmaE References G Blair Simulation of the CLIC Beam Delivery System Using BDSIM CLIC Note 509 Root User s Guide http root cern ch root doc RootDoc html Geant4 User s Guide http geant4 cern ch support userdocuments shtml MAD X User s Guide http mad home cern ch mad uguide html for example Basic course on Accelerator optics by Schmuesser Rossbach CERN Ac celerator school 8 see src BDSBunch cc for more details
4. BAS wate Mee TS ree 12 3 922 Spec key word n oo ee RUE a ee ee a ees 12 3 3 23 Element number 0 0 c cece e eee ees 12 3 3 24 Element attributes 00 e eee eee eee 13 3 3 25 Material table 0 0 cece cee tee eee 13 3 4 Run control and output 0 cee eee eee 14 SS 0 0 a a CR P e AC REAL AR RC RR 14 BALD Deam tach tte ten oett etes as atts de aieo dece 15 3 43 samples pie GA WRIST REG 15 ULM US eet edet dace aes Ani ee ee e SU ELTE OM NE Myers 15 AS MVisualizatiolis4s 74vesyRIARPEEDYSTRABXGGSN 16 D IDBVSICS cea x COR ee AAA OR E re s 17 9 1 physicsList option ssssusesslseeess hh 17 5 2 Transportation 2 ee RR PESE THREE Fa eg 17 9 9 Tracking accuracy o Rib cheba eT deena a 18 6 Output Analysis oss s c rr m 18 7 Implementation Notes 18 Tal AtChitecttre suse Ere Rd 18 7 2 Features to be added in next releases ooo o ooooooooo 18 Appendix A Geometry description formats 19 A l gmad format iii te eg ee a ERROR A eda 19 A2 WiokKas tie eni eane ei eva Ren areae fete ah eee Testes 20 A 2 1 Describing the geometry 0 00 cee eens 20 A 2 1 1 Common Table Parameters 00000 22 AOT 2 Box Solid Types mts a bate UD 24 A 2 1 3 Trapezoid Solid Types 00 eee eee ee 24 A 2 1 4 Cone Solid Types 0022 c cee cece eee eee 25 A 2 1 5 Torus Solid Types 00 c c
5. easier The syntax of a physical element declaration is element_name element_type attributes for example qd quadrupole 1 0 1 0 1 k1 0 01 element_type can be of basic type or inherited Allowed basic types are e marker e drift e rbend e sbend e quadrupole e sextupole e octupole e multipole e vkick e hkick e rf e rcol e ecol e solenoid e laser e transform3d e clement All elements except element are by default modeled by an iron cylinder given by the boxSize option with the vacuum beampipe defined by beampipeRadius option An already defined element can be used as a new element type The child element will have the attributes of the parent q quadrupole 1 1 m k1 0 1 qq q k1 0 2 3 3 1 Coordinate system The usual accelerator coordinate system is assumed see MAD page 29 Chapter 3 Lattice description 3 3 2 Units In GMAD the SI units are used length time angle quadrupole coefficient multipole coefficient 2n poles electric voltage electric field strength particle energy particle mass particle momentum beam current particle charge emittances m metres s seconds rad radians m m MV Megavolts MV m GeV GeV c GeV c A Amperes e elementary charges pi m mrad There are some predefined numerical values are pi 3 14159265358979 GeV 1 eV 107 KeV 10 9 MeV 1078 TeV 10 MV 1 Tesla 1 m 1 cm 107 mm 10
6. outer radius of the torus tube e RSWEPT Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the swept radius of the torus It is defined as being the distance from the center of the torus ring to the center of the torus tube For this reason this value should not be set to less than ROUTER e STARTPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the starting angle of the torus The default value is zero e DELTAPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the delta swept angle of the torus The default value is 2 PI A 2 1 6 Polycone Solid Types Append _POLYCONE to the table name in order to make use of the G4Polycone solid type The following table parameters are specific to the polycone solid e NZPLANES Variable type INTEGER 11 This is a required parameter This value will be used to specify the number of z planes to be used in the polycone This value must be set to greater than 1 e PLANEPOS1 PLANEPOS2 PLANEPOSN Variable type DOUBLE 10 3 These are required parameters These values will be used to specify the z position of the corresponding z plane of the polycone There should be as many PLANEPOS parameters set as the number of z planes For example 3 z planes will require that PLANEPOS1 PLANEPOS2 and PLANEPOS3 are all set up e
7. to SUBTRACT then the instead of placing the volume within the parent volume as an inherited object it will be subtracted from the parent volume in a boolean solid operation The default for this value is set to which sets to the usual mother daughter volume inheritance ALIGNIN Variable type INTEGER 11 This is an optional parameter If set to 1 then the placement of components will be rotated and translated such that the incoming beamline will pass through the z axis of this object The default is set to 0 ALIGNOUT Variable type INTEGER 11 This is an optional parameter If set to 1 then the placement of the next beamline component will be rotated and translated such that the outgoing beamline will pass through the z axis of this object The default is set to 0 SETSENSITIVE Variable type INTEGER 11 This is an optional parameter If set to 1 then the object will be set up to register energy depositions made within it and to also record the z position at which this deposition occurs This information will be saved in the ELoss Histogram if using ROOT output The default is set to 0 Appendix A Geometry description formats 23 e MAGTYPE Variable type VARCHAR 32 This is an optional parameter If supplied then the object will be set up to produce the appropriate magnetic field using the supplied K1 or K2 table parameter values Three magnet types are available QUAD SEXT and OCT The default i
8. 73 rad 1 mrad 107 S 1 ns 107 clight 2 99792458 x 108 for example one can write either 100 or 0 1 KeV when energy constants are concerned 3 3 3 marker marker has no effect but allows one to identify a position in the beam line say where a sampler will be placed It has no attributes Example mi marker see add var in parser gmad cc Chapter 3 Lattice description 6 3 3 4 drift drift defines a straight drift space Attributes e 1 length m default 0 e aper aperture m default same as beampipe radius Example d13 drift 1 0 5x m 3 3 5 rbend rbend defines a rectangular bending magnet Attributes e 1 length m default 0 e angle bending angle rad default 0 e B magnetic field T e aper aperture m default same as beampipe radius e outR external radius m of magnet default set to aper 1cm when B is set this defines a magnet with appropriate field strength and angle is not taken into account Otherwise B that corresponds to bending angle angle for a particle in use defined by the beam command with appropriate energy and rest mass is calculated and used in the simulations Example rbi rbend 1 0 5 m angle 0 01 3 3 6 sbend sbend defines a sector bending magnet Attributes e 1 length m default 0 e angle bending angle rad default 0 e B magnetic field T e aper aperture m default same as beampipe radius e outR extern
9. AddElement name symbol Z A method is called which in turns src BDSMaterials cc invokes the Geant4 G4Element constructor G4Element name symbol Z A In this case in src BDSDetectorConstruction cc the BDSMaterials AddMaterial name density state temp pressure list char itsComponents list lt G4int gt itsComponentsWeights method is called which in turns src BDSMaterials cc invokes the Geant4 G4Material constructor G4Material name density G4int itsComponents size state temp pressure Then each component is added with a call to the G4Material AddElement G4string G4int method In this case in src BDSDetectorConstruction cc the BDSMaterials AddMaterial name density state temp pressure list lt char gt itsComponents list G4double itsComponentsFractions method is called which in turns src BDSMaterials cc invokes the Geant4 G4Material constructor G4Material name density G4int itsComponents size state temp pressure Then each component is added with a call to the G4Material AddElement G4string G4double method Chapter 3 Lattice description 12 lt material gt matdef density lt double gt temperature lt double gt components lt list lt char gt gt componentsFractions lt list lt double gt gt Attributes density density in g cm3 e temperature temperature in K e components list of symbols for material components e componentsFractions mass fraction of
10. BDSIM User s Manual v0 4 I Agapov S Malton revision 0 4 last updated Jul 5 2007 Table of Contents BDSIM v0 4 User s Manual 1 1 About BDSIM 3 226522584 tees RIO 1 2 Obtaining Installing and Running 1 3 Lattice description suce emt axons alee 2 34 Program Structure id A Ie Iw See ak eae 2 3 2 Arithmetical expressions 0 00 00 eee e cece teen eens 3 3 3 Physical elements and Entities 00 0000 eee eee ee eee 4 3 3 1 Coordinate system 0 cece eects 4 3 9 2 UNS AS edt Ee da aie Rd 5 3J 0 90 Marker id gb a E pbi aeq a ae ug 9 9 95 udbplftois fe dag ue UH ia ute tt 6 0 9 9 SRDENG satire oh AA to update tl LA 6 3 9 0 SbONd stiri gie nien Xen ERE e eas 6 33 7 Quadrupole ise amen AR nh E Roe 7 320 0 sextupole Arise e ce tan PRU LO ERO an ae hea 7 3 9 0 SOCEUPO LC isis Wins tits ed des uev M aunts UE eee 7 3 9 10 MUL ti pole sists se Md hice naa a ae aay eee tun 8 ISLE TEA te Sek ee ace sd ween Wins oe NR SM RE 8 AS CO lusor es eo Le A La a artt Li eth ORA 8 3 39 13 TACO 4 sana A te ae ee ded FEES 9 OLA SOVENOLG cnet ee eyes aud E VE 9 3 3 15 hkick and Vkicky coc ies oad ok sana aves CREER 9 3 9 10 transtorm3d yo acc ees keeles ERR 9 SN element re vi ub es ee ad ee E 9 3218 Lines cen eoru ect al Re eae E P deme aera says 10 3 3119 materials incited A ea a oes Sed AR aai 10 3 39 20 Vaste terepen i ie ae ee goa ens wee PARE ac ug 12 SO 21
11. ETRY TYPE TABLE PARAMETER VARIABLE TYPE TABLE PARAMETER VARIABLE TYPE TABLE PARAMETER VARIABLE TYPE 3 Once a table has been created values must be entered into it in order to define the solids and position them The insertion command must appear after the table creation and must the MySQL compliant table insertion command Appendix A Geometry description formats 21 INSERT INTO TABLE NAME_GEOMETRY TYPE VALUES value1 value2 char value Qs The values must be inserted in the same order as their corresponding parameter types are described in the table creation Note that ALL length types must be specified in mm and that ALL angles must be in radians An example of two simple boxes with no visual attributes set is shown below The first box is a simple vacuum cube whilst the second is an iron box with length_x 10mm length_y 150mm length z 50mm positioned at x 1m y 0 z 0 5m and with zero rotation CREATE TABLE mytable_BOX NAME VARCHAR 32 MATERIAL VARCHAR 32 LENGTHX DOUBLE 10 3 LENGTHY DOUBLE 10 3 LENGTHZ DOUBLE 10 3 POSX DOUBLE 10 3 POSY DOUBLE 10 3 POSZ DOUBLE 10 3 ROTPSI DOUBLE 10 3 ROTTHETA DOUBLE 10 3 ROTPHI DOUBLE 10 3 INSERT INTO mytable_BOX VALUES a_box vacuum 50 0 50 0 50 0 0 0 0 0 0 0 0 0 0 0 0 0 INSERT INTO mytable_BOX VALUES another_box iron 10 0 150 0 50 0 1000 0 0 0 500 0 0 0 0 0 0 0 Further examples of the Mokka geometry impl
12. IAXIS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the Semiaxis in Y e LENGTHZ Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the height of the elliptical cone e ZCUT Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the upper cut plane level Note that the above parameters are used to define an elliptical cone with the following parametric equations in the usual Geant4 way x XSEMIAXIS LENGTHZ u u Cos v Y YSEMIAXIS LENGTHZ u u Sin v z u where v is between 0 and 2 PI and u between 0 and h respectively A 2 2 Creating a geometry list A geometry list is a simple file consisting of a list of filenames that contain geometry descriptions This is the file that should be passed to the GMAD file when defining the mokka element An example of a geometry list containing boxes sql and cones sql would be 4 symbols can be used for commenting out an entire line directory boxes sql directory cones sql Appendix C Bunch description formats 28 A 2 3 Defining a Mokka element in the gmad file The Mokka element can be defined by the following command lt element_name gt element geometry format filename attributes where format must be set to mokka and filename must point to a file that contains a list of files that have the geometry descriptions for
13. RINNER1 RINNER2 RINNERN Variable type DOUBLE 10 3 These are required parameters These values will be used to specify the inner radius of the corresponding z plane of the polycone There should be as many RINNER parameters set as the number of z planes For example 3 z planes will require that RINNER1 RINNER2 and RINNERS are all set up e ROUTER1 ROUTER2 ROUTERN Variable type DOUBLE 10 3 These are required parameters These values will be used to specify the outer radius of the corresponding z plane of the polycone There should be as many ROUTER parameters set as the number of z planes For example 3 z planes will require that ROUTER ROUTER2 and ROUTERS are all set up Appendix A Geometry description formats 27 e STARTPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the starting angle of the polycone The default value is zero e DELTAPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the delta angle of the polycone The default value is 2 PI A 2 1 7 Elliptical Cone Solid Types Append _ELLIPTICALCONE to the table name in order to make use of the G4Ellipticalcone solid type The following table parameters are specific to the elliptical cone solid e XSEMIAXIS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the Semiaxis in X e YSEM
14. al radius m of magnet default set to aper lcm The meaning of B and angle is the same as for rbend Example sbi sbend 1 0 5 m angle 0 01 Chapter 3 Lattice description 7 3 3 7 quadrupole quadrupole defines a quadrupole Attributes 1 length m default 0 k1 normal quadrupole coefficient k1 1 B rho dB dx m Positive k1 means horizontal focusing of positively charged particles default 0 ksi skew quadrupole coefficient ks1 1 B rho dB dx m where x y is now a coordinate system rotated by 45 degrees around s with respect to the normal one default 0 tilt roll angle rad about the longitudinal axis clockwise aper aperture m default same as beampipe radius outR external radius m of magnet default set to aper 1cm Example qf quadrupole 1 0 5 m ki 0 5 tilt 0 01 3 3 8 sextupole sextupole defines a sextupole Attributes 1 length m default 0 k2 normal sextupole coefficient k2 1 B rho d B da m ks2 skew sextupole coefficient ks2 1 B rho d4 B dx m where x y is now a coordinate system rotated by 30 degrees around s with respect to the normal one default 0 tilt roll angle rad about the longitudinal axis clockwise aper aperture m default same as beampipe radius outR external radius m of magnet default set to aper 1cm Example sf sextupole 1 0 5 m k2 0 5 tilt 0 01
15. e first has to define the beamline geometry in a file which is then passes to bdsim via the file command line option for example bdsim file line gmad output root batch The next section describes how to do it in more detail 3 Lattice description The beamline beam properties and physics processes are specified in the input file written in the GMAD language which is a variation of MAD language extended to handle sophisti cated geometry and parameters relevant to radiation transport GMAD is described in this section Examples of input files can be found in the BDSIM distribution in the examples directory In order to convert a MAD file into a GMAD one a utility called mad2gmad sh is provided in the utils directory The following MAD commands are not supported e assign e bmpm e btrns e envelope e optics e option e plot e print e return e survey e title e twiss The following MAD commands e moni e monitor e wire e prof are replaced with the marker command 3 1 Program structure A GMAD program consists of a sequence of element definitions and control commands For example tracking a 1 GeV electron beam through a FODO cell will require a file like this qf quadrupole 1 0 5 m k1 0 1 qd quadrupole 1 0 5 m k1 0 1 Chapter 3 Lattice description 3 d drift 1 0 5x m fodo line qf d qd d use period fodo beam particle e energy 1 GeV Generally the user has to define a sequ
16. each component in material unit in order Again the kStateSolid state and a normal pressure of 1 atm are assumed Example samarium atom symbol Sm z 62 a 150 4 cobalt atom symbol Co z 27 a 58 93 SmCo matdef density 8 4 temperature 300 0 Sm Co 0 338 0 662 3 3 20 laser laser defines a drift section with a laser beam inside The laser is considered to be the intersection of the laser beam with the volume of the drift section Attributes e 1 length of the drift section m e x y z components of the laser direction vector e wavelength laser wave length m 3 3 21 gas 3 3 22 spec keyword Starting from v0 3 it is possible to add the spec keyword to all element definition Spec keywordi valuei amp keyword2 value2 amp By this means any set of keyword value pairs can be passed to the accelerator component construction classes qd mquad 1 0 5 m k1 qdk1 spec type cylinder 3 3 23 Element number When several elements with the same name are present in the beamline they can be accessed by their number in the sequence In the next example the sampler is put before the second drift Chapter 3 Lattice description 13 bl line d d d sample range d 2 3 3 24 Element attributes Element attributes such as length multipole coefficients etc can be accessed by putting square brackets after the element name e g x d 1 3 3 25 Material table There is a set of predefined
17. ece eee eee eee 25 A 2 1 6 Polycone Solid Types 00 0 eee eee ee eee 26 A 2 1 7 Elliptical Cone Solid Types 22000 27 A 2 2 Creating a geometry list oooooooommmmm m 27 A 2 3 Defining a Mokka element in the gmad file 28 A3 d 2e 8 os ct hy ate lng ois esters a EE E N see wate 28 Appendix B Field description formats 28 Appendix C Bunch description formats 28 S References voe vace o RECESSU X EE NOE 29 11 Chapter 2 Obtaining Installing and Running 1 BDSIM v0 4 User s Manual This file is updated automatically from manual texi last updated on Jul 5 2007 1 About BDSIM BDSIM is a Geant4 extension toolkit for simulation of particle transport in accelerator beamlines It provides a collection of classes representing typical accelerator components a collection of physics processes for fast tracking procedures of on the fly geometry construction and interfacing to ROOT analysis 2 Obtaining Installing and Running BDSIM can be downloaded from http ilc pp rhul ac uk bdsim html This site also contains some information on planned releases and other issues Alternatively a develop ment version is accessible under http cvs pp rhul ac uk Download the tarball and extract the source code Make sure Geant4 is installed and appropriate environment vari ables defined Then go through the configuration procedure by running the configure scrip
18. ementation can be found in the exam ples Mokka General directory See the common table parameters and solid type sections below for more information on the table parameters available for use Appendix A Geometry description formats 22 A 2 1 1 Common Table Parameters The following is a list of table parameters that are common to all solid types either as an optional or mandatory parameter NAME Variable type VARCHAR 32 This is an optional parameter If supplied then the Geant4 LogicalVolume associated with the solid will be labelled with this name The default is set to be the table s name plus an automatically assigned volume number MATERIAL Variable type VARCHAR 32 This is an optional parameter If supplied then the volume will be created with this material type note that the material must be given as a character string inside double quotation marks The default material is set as Vacuum PARENTNAME Variable type VARCHAR 32 This is an optional parameter If supplied then the volume will be placed as a daughter volume to the object with ID equal to PARENTNAME The default parent is set to be the Component Volume Note that if PARENTID is set to the Component Volume then POSZ will be defined with respect to the start of the object Else POSZ will be defined with respect to the center of the parent object INHERITSTYLE Variable type VARCHAR 32 This is an optional parameter to be used with PARENTNAME If set
19. ence of elements with drift quadrupole line etc then select the beamline with the use command and specify beam parameters and other options with beam and option commands The sample command controls what sort of information will be recorded during the execution The parser is case sensitive However for convenience of porting lattice descriptions from MAD the keywords can be both lower and upper case The GMAD language is discussed in more detail in this section 3 2 Arithmetical expressions Throughout the program a standard set of arithmetical expressions is available Every expression is ended with a semicolon for example x 1 y 2 5 x z sin x log y 8e5 Several expressions can be grouped into one block by means of the 4 and symbols or the begin and end keywords Available binary operators are Available unary operators are Available boolean operators are lt gt lt gt lt gt Available functions are e sqrt e cos e sin e exp e log e tan e asin e acos e abs l see add_func in parser gmad cc Chapter 3 Lattice description 4 3 3 Physical elements and Entities GMAD implements almost all the standard MAD elements but also allows to define ar bitrary geometric entities and magnetic field configurations The geometry description capabilities are extended by using drivers to other geometry description formats which makes interfacing and standardisation
20. esIgnore synchRadOn srTrackPhotons srLowX srLowGamE minimumEpsilonStep maximumEpsilonStep delta neStep prodCutPhotons prodCutPhotonsP prodCutElectrons prodCutElectronsP prodCutPositrons prodCutPositronsP chord finder precision boundary intersection precision minimum step size element overlap safety charged particle cutoff energy photon cutoff energy seed for the random number generator setting to 1 uses the system clock to generate the seed if set tracks are terminated after interaction with material and energy deposit recorded determines the set of physics processes used number of primary particles fired when in batch mode number of events recorded per file number of lines to skip when reading bunch files turn on Synchrotron Radiation process whether to track the SR photons Sets lowest energy of SR to X E critical lowest energy of propagating SR photons minimum relative error acceptable in stepping maximum relative error acceptable in stepping set position error acceptable in an integration steps standard overall production cuts for photons precision production cuts for photons in element standard overall production cuts for electrons precision production cuts for electrons in element standard overall production cuts for positrons precision production cuts for positrons in element Chapter 4 Visualization 15 For a more detailed description of how the option influence the tracking see Chapter 5 Physics
21. example collimator element geometry mokka coll_geomlist sql A 3 gdml GDML is a XML schema for detector description GDML will be supported as an external format starting from next release Appendix B Field description formats The element with user defined physical geometry is defined by command lt element_name gt element geometry format filename attributes for example colli element geometry plain colli geom Appendix C Bunch description formats For compatibility with other simulation codes following bunch formats can be read For example to use the file distr dat as input the beam definition should look like beam particle e distrType guineapig bunch distrFile distr dat The formats currently supported are listed below e guineapig bunch E GeV x micrometre y micrometre z micrometre x microrad y microrad e guineapig slac E GeV x rad y rad z nanometre x nanometre y micrometre e guineapig pairs E GeV x rad ylrad z rad x nanometre y nanometre z nanometre here a particle with E gt 0 is assumed to be an electron and with E 0 a positron e cain A custom distribution file format can be specified in the form distrType fieldi uniti fieldi1 uniti For instance 7 see src BDSBunch cc for more details Chapter 8 References 29 beam particle e energy ener GeV nparticles 1e 3 distrType pt 1 E GeV xp rad yp rad z mum x nm y nm
22. h future versions of BDSIM will also support online querying of MySQL databases Note that throughout any of the Mokka files a may be used to represent a commented line There are three key stages which are detailed in the following sections that are required to setting up the Mokka geometry e Describing the geometry e Creating a geometry list e Defining a Mokka Element to load geometry descriptions from a list A 2 1 Describing the geometry An object must be described by creating a MySQL file containing commands that would typically be used for uploading creating a database and a corresponding new table into a MySQL database BDSIM supports only a few such commands specifically the CREATE TABLE and INSERT INTO commands When writing a table to describe a solid there are some parameters that are common to all solid types such as NAME and MATERIAL and some that are more specific such as those relating to radii for cone objects A full list of the standard and specific table parameters as well as some basic examples are given below with each solid type All files containing geometry descriptions must have the following database creation commands at the top of the file DROP DATABASE IF EXISTS DATABASE_NAME CREATE DATABASE DATABASE_NAME USE DATABASE_NAME A table must be created to allow for the insertion of the geometry descriptions A table is created using the following MySQL compliant commands CREATE TABLE TABLE NAME_GEOM
23. he BDSMaterials AddMaterial name Z A density method is called which in turns src BDSMaterials cc invokes the Geant4 G4Material constructor G4Material name Z A density Chapter 3 Lattice description If the material is made up by several components first of all each of them must be specified with the atom keyword 4 lt element gt atom Z lt int gt A lt double gt symbol lt char gt Attributes e Z atomic number e A mass number g mol e symbol atom symbol Then the compound material can be specified in two manners 1 If the number of atoms of each component in material unit is known the following syntax can be used lt material gt matdef density lt double gt temperature lt double gt components lt list lt char gt gt componentsWeights lt list lt int gt gt Attributes e density density in g cm3 e temperature temperature in K e components list of symbols for material components e componentsWeights number of atoms of each component in material unit in order The kStateSolid state and a normal pressure of 1 atm are assumed Example niobium atom symbol Nb z 41 a 92 906 titanium atom symbol Ti z 22 a 47 867 NbTi matdef density 5 6 temperature 4 0 Nb Ti 1 1 2 On the other hand if the mass fraction of each component is known the following syntax can be used In this case in src BDSDetectorConstruction cc the BDSMaterials
24. materials for use in elements such as collimators e g e Air e Aluminium e BeamGasPlugMat e Beryllium e CarbonMonoxide e CarbonSteel e Concrete e Copper e Graphite e Invar e Tron e Laser Vac e Lead e LeadTungstate e LiquidHelium e NbTi e Niobium e Silicon e SmCo e Soil e Titanium e TitaniumAlloy e Tungsten e Vacuum e Vanadium e Water e WeightIron For more details see the file src BDSMaterials cc Chapter 3 Lattice description 14 3 4 Run control and output The execution control is performed in the GMAD input file through option and sample commands How the results are recorded is controlledby the sample command When the visualization is turned on it is also controlled through Geant4 command prompt 3 4 1 option Most of the options in bdsim are set up by the command option lt name gt value The following options influence the geometry beampipeRadius beampipeThickness tunnelRadius boxSize default beampipe radius m default beampipe thickness m tunnel Radius m default accelerator component size m The following options influence the tracking deltaChord deltaIntersection chordStepMinimum lengthSafety thresholdCutCharged thresholdCutPhotons randomSeed stopTracks physicsList ngenerate nperfile nlin
25. n into account To do this the user has to describe the collimator with the generic type element Attributes e 1 length m default 0 e xsize horisontal aperture m e ysize vertical aperture m e material material e outR limits external extent m of collimator default set to aper 1cm Example coli rcol 1 0 4 m xsize 2 mm ysize i mm material W Chapter 3 Lattice description 9 3 3 13 ecol ecol defines an elliptical collimator Here again the longitudinal collimator structure is not taken into account Attributes e 1 length m default 0 e xsize horisontal aperture m e ysize vertical aperture m e material material e outR limits external extent m of collimator default set to aper 1cm Example col2 ecol 1 0 4 m xsize 2 mm ysize i mm material W 3 3 14 solenoid Not yet implemented 3 3 15 hkick and vkick hkick and vkick are equivalent to a rbend and an rbend rotated by 90 degrees respectively 3 3 16 transform3d An arbitrary 3 dimensional transformation of the coordinate system is done by placing a transform3d element in the beamline Attributes e x lt x offset e y Xy offset e z lt z offset e phi phi Euler angle e theta theta Euler angle e psi psi Euler angle Example rot transform3d psi pi 2 3 3 17 element All the elements are in principle examples of a general type element which can represent an arbitra
26. n this value will be used to specify the inner radius of the start of the cone The default value is zero RINNEREND Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the inner radius of the end of the cone The default value is zero ROUTERSTART Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the outer radius of the start of the cone ROUTEREND Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the outer radius of the end of the cone STARTPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the starting angle of the cone The default value is zero DELTAPHI Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the delta angle of the cone The default value is 2 PI A 2 1 5 Torus Solid Types Append _TORUS to the table name in order to make use of the G4Torus solid type The following table parameters are specific to the torus solid RINNER Variable type DOUBLE 10 3 This is an optional parameter If set then this value will be used to specify the inner radius of the torus tube The default value is zero ROUTER Variable type DOUBLE 10 3 Appendix A Geometry description formats 26 This is a required parameter This value will be used to specify the
27. ne Note This command is not necessary in exampleNOS3 since the C method DrawTrajectory is described in the event action vis viewer set viewpointThetaPhi 90 90 vis drawVolume vis scene add trajectories tracking storeTrajectory 0 vis viewer zoom tracking storeTrajectory 1 for BDS vis viewer zoom 300 vis viewer set viewpointThetaPhi 3 45 By default the macro is read from the file named vis mac The name of the file with the macro can also be passed via the vis_mac switch bdsim file line gmad vis_mac my_macro mac In interactive mode all the Geant4 interactive comamnds are available For instance to fire 100 particles type run beamOn 100 runs the simulation with 100 particles and to end the session type exit To display help menu Chapter 5 Physics 17 help For more details see Geant page 29 5 Physics BDSIM can exploit all physics processes that come with Geant4 In addition fast tracking inside multipole magnets is provided More detailed description of the physics is given below 5 1 physicsList option Depending on for what sort of problem BDSIM is used different sorts of physics processes should be turned on This processes are groupes into so called physics lists The physics list is specified by the physicsList option in the input file e g option physicsList em standard Several predefined physics lists are available standard transportation of prima
28. pole gmad Physics list adding own physics processes 7 2 Features to be added in next releases current development is focused on the beam gas scattering and implementation of wake fields Appendix A Geometry description formats 19 Appendix A Geometry description formats The element with user defined physical geometry is defined by lt element_name gt element geometry format filename attributes for example colli element geometry gmad colli geo A 1 gmad format gmad is a simple format used as G4geometry wrapper It can be used for specifying more or less simple geometries like collimators Available shapes are Box x0 x_origin y0 y_origin z0 z_origin x xsize y ysize z zsize material MaterialName temperature T Tubs x0 x_origin y0 y_origin z0 z_origin x xsize y ysize z zsize material MaterialName temperature T For example Cons x0 0 y0 0 z0 0 rmini 5 rmax1 500 rmin2 5 rmax2 500 z 250 material Graphite phi0 0 dphi 360 temperature 1 Appendix A Geometry description formats 20 A file can contain several objects which will be placed consequently into the volume A user has to make sure that there is no overlap between them A 2 mokka As well as using the gmad format to describe user defined physical geometry it is also possible to use a Mokka style format This format is currently in the form of a dumped MySQL database format althoug
29. rapezoid with the X and Y dimensions varying along z functions The following table parameters are specific to the trapezoid solid LENGTHXPLUS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the x extent of the box s dimensions at the surface positioned at dz LENGTHXPMINUS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the x extent of the box s dimensions at the surface positioned at dz LENGTHYPLUS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the y extent of the box s dimensions at the surface positioned at dz LENGTHYPMINUS Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the y extent of the box s dimensions at the surface positioned at dz LENGTHZ Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the z extent of the box s dimensions Appendix A Geometry description formats 25 A 2 1 4 Cone Solid Types Append _CONE to the table name in order to make use of the G4Cons solid type The following table parameters are specific to the cone solid LENGTH Variable type DOUBLE 10 3 This is a required parameter This value will be used to specify the z extent of the cone s dimensions RINNERSTART Variable type DOUBLE 10 3 This is an optional parameter If set the
30. rdStepMinimum minimum chord length for the step deltaIntersection determines the precision of locating the point of intersection of the particle trajectory with the boundary and hence the error in the path length in each volume This may influence the results especially in the case when EM fields are present deltaChord lengthSafety all volumes will have an additional overlap of this length thresholdCutCharged energy below which charged particles are not tracked thresholdCutPhotons energy below which photons are not tracked 6 Output Analysis During the execution the following things are recorded e energy deposition along the beamline e sampler hits If the output format is ASCII i e if BDSIM was invoked with the output ascii option then the output file output txt containing the hits will be written which has rows like hits PDGtype p GeV c x micron y micron z m x nicrorad y nicrorad 11 250 4 72907 5 86656 5 00001e 06 00 11 250 8 17576 4 99729 796 001 0 320334 0 126792 If ROOT output is used then the root files output O root output 1 root etc will be created with each file containing the number of events given by nperfile option The file contains the energy loss histogram and a tree for every sampler in the line with self explanatory branch names 7 Implementation Notes 7 1 Architecture In this section the architecture of BDSIM is briefly described for someone wishing to use it as a class library BDSMulti
31. rs They are the Euler angles in radians used to rotate the obejct before it is placed The default is set to zero for each angle e RED BLUE GREEN Variable type DOUBLE 10 3 These are optional parameters They are the RGB colour components assigned to the object and should be a value between 0 and 1 The default is set to zero for each colour e VISATT Variable type VARCHAR 32 This is an optional parameter This is the visual state setting for the object Setting this to W results in a wireframe displayment of the object S produces a shaded solid and I leaves the object invisible The default is set to be solid Appendix A Geometry description formats 24 FIELDX FIELDY FIELDZ Variable type DOUBLE 10 3 These are optional parameters They can be used to apply a uniform field to any volume with default units of Tesla Note that if there is a solenoid field present throughout the enitre element then this uniform field will act in addition to the solenoid field A 2 1 2 Box Solid Types Append _BOX to the table name in order to make use of the G4Box solid type The following table parameters are specific to the box solid LENGTHX LENGTHY LENGTHZ Variable type DOUBLE 10 3 These are required parameters There values will be used to specify the box s dimen sions A 2 1 3 Trapezoid Solid Types Append _TRAP to the table name in order to make use of the G4Trd solid type which is deined as a t
32. ry geometric entity with arbitrary B field maps Attributes e geometry geometry description e bmap bmap description e outR limits external extent component box size default set to aper 1cm Chapter 3 Lattice description 10 Descriptions are of the form format filename where filename is the path to the file with the geometry description and format defines the geometry description format The possible formats are given in Appendix A Geometry page 19 Example qq element geometry mokka qq sql bmap mokka qq bmap 3 3 18 line elements are grouped into sequences by the line command line_name line element_1 element_2 where element_n can be any element or another line Example A sequence of FODO cells can be defines as qf quadrupole 1 0 5 k1 0 1 qd quadrupole 1 0 5 k1 0 1 d drift 1 0 5 fodo line qf d qd d section line fodo fodo fodo beamline line section section section 3 3 19 materials To define a material the matdef keyword must be used If the material is composed by a single element it can be defined using the following syntax material matdef Z lt int gt A lt double gt density lt double gt Attributes e Z atomic number e A mass number g mol e density density in g cm3 e temperature temperature in K Example iron matdef Z 26 A 55 845 density 7 87 In this case in src BDSDetectorConstruction cc t
33. ry particles only em standard transporation of primary particles ionization bremsstrahlung multiple scattering em low the same but using low energy electromagnetic models em muo the same but using biased muon cross sections lw list for laser wire simulation standard electromagnetic physics and laser wire physics which is Compton Scattering with total cross section renormalized to 1 hadronic standard standard electromagnetic fission neutron capture neutron and proton elastic and inelastic scattering By default the standard physics List is used 5 2 Transportation The transportation follows the scheme the step length is selected which is defined either by the distance of the particle to the boundary of the logical volume it is currently in which could be e g field boundary material boundary or boundary between two adjacent elements or by the mean free path of the activated processes Then the particle is pushed to the new position and secondaries are generated if necessary Each volume has an associated transporatation algorithm For an on energy particle travelling close to the optical axis of a quadrupole dipole or a drift standard matrix transportation algorithms are used Course page 29 For multipoles of higher orders and for off axis energy particles Runge Kutta methods are used Appendix A Geometry description formats 18 5 3 Tracking accuracy The following options influence the tracking accuracy cho
34. s set to no magnet type Note that if MAGTYPE is set to a value whilst K1 K2 K3 are not set then no magnetic field will be implemented e Ki Variable type DOUBLE 10 3 This is an optional parameter If set to a value other than zero in conjuction with MAGTYPE set to QUAD then a quadrupole field with this K1 value will be set up within the object Default is set to zero e K2 Variable type DOUBLE 10 3 This is an optional parameter If set to a value other than zero in conjuction with MAGTYPE set to SEXT then a sextupole field with this K2 value will be set up within the object Default is set to zero e K3 Variable type DOUBLE 10 3 This is an optional parameter If set to a value other than zero in conjuction with MAGTYPE set to OCT then a sextupole field with this K3 value will be set up within the object Default is set to zero e POSX POSY POSZ Variable type DOUBLE 10 3 These are required parameters They are form the position in mm used to place the object in the component volume POSX and POSY are defined with respect to the center of the component volume and with respect to the component volume s rotation POSZ is defined with respect to the start of the component volume Note that if the object is being placed inside another volume using PARENTNAME then the position will refers to the center of the parent object e ROTPSI ROTTHETA ROTPHI Variable type DOUBLE 10 3 These are optional paramete
35. t configure It will create a Makefile from template defined in Makefile in You may want to edit the Makefile manually to meet your needs if your CLHEP version is greater than 2 x put DCLHEP_VERSION 9 Then start the compilation by typing make If the compilation is successful bdsim executable should be created in the current di rectory or in the G4WORKDIR directory in case this variable is defined Next set up the DY LD_LIBRARY_PATH variable to point to the parser directory and to the directory where libbdsim so is BDSIM is invoked by the command bdsim options where the options are file lt filename gt specify the lattice file output fmt output format rootlascii default ascii outfile lt file gt output file name Will be appended with _N where N 0 1 2 3 etc vis mac file visualization macro script default vis mac help display this message verbose display general parameters before run verbose event display information for every event verbose step N display tracking information after each step verbose event num display tracking information for event number N batch batch mode no graphics outline lt file gt print geometry optics info to lt file gt outline_type lt fmt gt type of outline format where fmt optics survey Chapter 3 Lattice description 2 materials list materials included in bdsim by default To run bdsim on
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