H8 user manual - NA handbook
Contents
1. XTRI042198 TRIG1 TRIG1 Before COLL5 6 XTRI042410 TRIG2 TRIG2 After COLL8 9 XTRI042463 TRIG3 TRIG3 Pair of counters around XCET042474 upstream of NA45 XTRI042475 TRIG4 TRIG4 XTRI042532 TRIG5 Pair of counters around XCET042539 in H8A upstream of ATLAS test area XTRI042543 TRIG5 TRIG6 XTRI042544 TRIG7 Small XTRI for use with XEMC XTRI042574 TRIG6 TRIG8 Behind the XTDV in H8B area C 2 Steering Magnets Table C 2 BEATCH name Old Name Current Name H V Comment MDXH042133 TRIMI TRIM1 H Steer onto COLL5 6 and to micro collimator MDXV042134 TRIM2 TRIM2 V MDXH042203 TRIM3 TRIM3 H Steer onto COLL8 MDXH042318 TRIM7 TRIM5 H MDXV042407 TRIM4 TRIM6 V Steer onto COLL9 MDXH042462 TRIM5 TRIM7 H Steer onto NA45 MDXV042463 TRIM6 TRIM8 V MDSV042529 TRIM8 TRIM10 V Steer onto ATLAS H8A MDSH04530 TRIM9 TRIM9 H C Beam Elements 17 H8 User Guide SPS Beam Line 23 May 2002 18 C Beam Elements H8 SPS Beam Line User Guide 23 May 2002 D Beam Focusing onto ATLAS Test Setups In the 2000 filter mode optics of H8 the following current settings allow to change the focuss ing in the ATLAS region H8A and H8B zones The values given are for a 300 GeV c beam scale the current values with momentum for any other momenta including the sign Table D 1 Condition Q16 A Q17 A Q18 A Focus at MWPC5 6 265 2 294 2 265 2 Parallel in ATLAS tests 263 6 149 2 0 Focus 5 5m upstream of MSP 236 0 281 02. CERN European Laboratory for Particle Physics SL Division Experimental Areas Group CH 1211 Geneva 23 Switzerland HO SPS Beam Line User Guide Issue Revision Reference Created Last modified Prepared By Draft 0 ATLAS TDR xx 10 October 1996 10 October 1996 ATLAS XYZ Collaboration H8 User Guide SPS Beam Line 23 May 2002 All trademarks copyright names and products referred to in this document are acknowledged as such H8 User Guide SPS Beam Line 23 May 2002 Table Of Contents 1 The Layout of the H8 Beam Sn 1 11 Different modes of H8 operation 1 1 2 Beams available in H8 2 1 3 Experimental areas in H8 2 2 The Control Tree 2 3 Beam Files 3 4 Fine Steering and Focussing of the Beam 4 5 Beam Intensity and Momentum Spread 4 6 The type of particles in your beam 5 7 Access to your zone 6 7 1 SPECIAL features in zone e 168 8 8 Using the detectors beam tuning 8 9 Further problems 10 10 Special Beams EEE BEN 10 10 1 H8 operation as 450 Gev microbeam 10 10 1 1 Interlock conditions Br 10 10 2 TAX5 two options for the microbeam 11 10 3 Tuning the microbeam 11 A Modification History Bi 13 A 1 H8 Beam updates during 2000 13 A 2 REVIEW of your pastruns 13 B Experimental Scalers 15 C Beam Elements 17 C 1 Trigger Counters 17 C2 Steering Magnets 17 D Beam Focusing onto ATLAS Test Setups 19 E Oper
3. return leaves the old comment Alterna tively the whole BIM 0 present setting can be saved with the FILES SAVE H8 nn command Explanation of NORM s Two or more normalisation counters are available Norm 0 simply the time for normalisation Norm 1 Interaction rate in primary target T4 Norm 2 Incident rate on primary target T4 Usually it is recommended to use Norm 2 H8 User Guide SPS Beam Line 23 May 2002 9 Further problems 1 The HELP command gives you a general list of questions and suggestions on what to do even though it might not be specific to your beamline only it could still be of use A general check of magnets and collimators is obtained by STATUS CHECK which indicates wrong values in these beamline elements Use also STATUS GENERAL to make sure that you are in a correct beam mode secondary tertiary muons etc 2 Under INFO LOGBOOK you find the last changes to magnet currents and collimator settings and traces of other action related to your beam You may find hints to what went wrong 3 Run the STATUS CHECK and STATUS MODE to assure that no magnet nor collimator has failed and verify the precise status of the beam In particular this could help to see why you don t get electrons etc 4 Note that there is a manual vacuum valve in the NA45 zone door 138 If you are not happy with the quality of your beam in particular electrons make sure that valve
4. 263 0 Focus 5m downstream of MSP 305 8 218 0 0 Focus 10m downstram of MSP 302 6 207 0 0 Focus 20m downstream of MSP 297 4 198 2 0 Focus 30m dowstream of MSP 293 6 191 8 0 Focus 40m downstream of MSP 290 4 186 8 0 Focus at MNP17 288 4 183 4 0 D Beam Focusing onto ATLAS Test Setups 19 H8 User Guide SPS Beam Line 23 May 2002 20 D Beam Focusing onto ATLAS Test Setups H8 User Guide SPS Beam Line 23 May 2002 E Operation for very low Beam Energies In order to allow the operation of the beam at energies lower than achieved before the 6 main vertical bending magnets MBN s BEND1 2 3 and 4 have been recabled during the 1996 97 shutdown in the following way see also the figure attached Table E 1 previously now as of 1997 B1 A B1 A B1 B B2 A B1 C B2 B B2 A Bi B B2 B B1 C B2 C B2 C B3 A B3 A B3 B B4 A B3 C B4 B B4 A B3 B B4 B B3 C B4 C B4 C This allows to run the beam with currents I B1 0 I B3 0 and 1 B2 21 1 B4 21 while previ ously all currents were set to Ip As a result the point of deflection is no longer in the centre of the 6 large bending magnets is no longer in the middle of them but slightly offset This has as a consequence that the beam is vertically offset e g by about 30 mm in collimator C6 and is back on axis again only in colli mator C9 The beamfiles for this very low energy running are specially marked in the comment line and should not be cha
5. etc are removed from the beam Separation of electrons from hadrons is achieved by the synchrotron radiation energy loss in the big BENDs followed by collimation of the hadrons The effect is very strongly energy dependent Example separation of pions and elec trons at 200 GeV is 16 mm at collimator C9 in H8 Note Limited purity of this beam has been observed in particular in positive polarity The electrons are however focussed in the centre of the beam while pions and muons occupy a larger phase space It has been found that the best purity in the experiment is obtained if the secondary pion beam is used first for steering onto the experimental counters then copying the TRIM values found for the electron case An increased purity is expected as of 2000 due to the addition of C7 which precedes C9 and should always the same jaw positions as it H8 SPS Beam Line User Guide 23 May 2002 tertiary beams Pure hadrons secondary beams tertiary beams Are obtained by loading the appropriate file and choosing Pb as a TARGET see below Downstream of this target all other Pb sheets and TRIGs should be out of the beam Momentum selection of the tertiary beam in second main BEND separation from hadrons due to production mechanism in the Pb foil TARGET degrading electrons by bremsstrahlung much more the hadrons Choose the appropriate beam file and put in the Pb TARGET to remove electrons In addition further
6. 7 1 SPECIAL features in zone 168 The motorized beam dump separating 158 from 168 allows access to the 168 H8B area at any time without stopping the beam in zone 158 H8A Exception High Intensity run ning of H8 the zone 168 will be fully interlocked and the beam stopped in the tunnel when access is requested on 168 e The garage of H8B for the preparation modification of the Lar endcap modules and cry ostat can be opened by opening door PPG168 using a normal key taken with the stand ard access procedure at door PPE168 However opening this large door which potentially allows a lot of people to enter the area in a short time will create a special FREE condition in zone 168 requiring a search including a special search box located in the far corner Jura side of the H8B zone e The timer of zone PPE168 has been set to 5 minutes to allow the search 8 Using the detectors beam tuning The H8 beam is equipped with various detectors CALO CET XWCA MWPC FISC For experts only a lead glass block with a PM can be moved into the beam upstream of ATLAS H8A A pulse height spectrum of this detector allows a rough estimation of the beam composition in particular electrons vs hadrons in one burst Two Threshold Cerenkov counters see the description on the EA pages on http nicewww cern ch slleagroupleahome html Control via branch DETECTORS THRESH Wire chambers that allow to make beam profiles They on
7. E Operation for very low Beam Energies 23 H8 User Guide SPS Beam Line 23 May 2002 24 This document has been prepared with Release 6 0 of the Adobe FrameMaker Technical Publishing System using the Technical Design Report template prepared by Mario Ruggier of the Information and Programming Techniques Group ECP Division CERN modified to suit the manual style by Ilias Efthymiopoulos SL EA group To facilitate multiple author editing and electronic distribution of documents only widely available fonts have been used The principal ones are Running text Palatino 10 5 point on 13 point line spacing Chapter headings Helvetica Bold 18 point 2nd 3rd and 4th level headings Helvetica Bold 14 12 and 10 point respectively Figure and table captions Helvetica 9 point
8. condition TAX6 20 mm approx corresponds to a 2 mm hole In addition to this TAX RANGE condition the following conditions have to be fulfilled for mi crobeam operation collimator XCIO200 has to be IN This is a 3 mm collimator with fixed openings just upstream of the microcollimator microcollimator table has to belN Tthis is a manual operation needs vacuum intervention and the status is obtained from a switch microcollimator openings have to be smaller than 1 mm Under these conditions the main bending magnets R22D 14 andR22D 15 can be allowed to go to maximum current unlimited and H8 is considered to be in a legal status 10 2 TAX5 two options for the microbeam There are in fact two options for TAX5 TAX5 20 mm 12mm hole filled with a 80 cm long Be rod e medium intensity microbeam up to about 5 106 protons per burst TAX5 140 mm 80 mm hole e high intensity microbeam more than 107 protons per burst Note that TAX5 and TAX6 140 mm is the condition for access 10 3 Tuning the microbeam Intensity Use the opening of the microcollimators C12 C13 WARNING might cause interlock problem because of e limit to 1 mm aperture if so close to 0 2 mm wait for e interlock conditions to be o k and start opening C12 C13 in small steps Beam position at NA45 use TRIM35 hor TRIM6 vert Beam position at RD21 use TRIMO hor TRIMS8 vert Beam focussing at NA45 use Q14 and Q15 beam focuss
9. file loaded collimator and TRIG status etc this will allow you to judge whether you are in a strange mode or not A more complete picture can be obtained by using STATUS MODE H8 User Guide SPS Beam Line 23 May 2002 4 Fine Steering and Focussing of the Beam BENDs Steering of a beam is done by BENDing magnets dipoles Normally the currents in the dipole magnets are defined correctly in the beam files and the user should not modify them without discussing with the EA physicists QUADs Quadrupoles are like lenses in conventional optics they are used to de focus the beam and thus change the spot size of the beam The spot size of the beam is con trolled by the last QUADs in front of each experiment Which quad controls what projection depends on the beam file used In the beam files these quads are usually defined to minimise the spot size at the main experiment locations Note different users may choose a different beam spot size the quadrupole values saved in the files are therefore not always the ones you like in H8A H8B this concerns mostly the values of Q17 and Q18 cf Appendix 3 TRIMs Trim magnet are correction dipoles used for fine steering of the beam Normally the last TRIMs upstream of each experiment should only be used for steering Typ ical values for TRIM10 vertical and TRIM9 horizontal steering to ATLAS Tiles are 23 mm for a 100 A change at 100 GeV c beam momentum proportional to p and inversely p
10. G counters had to be re numbered On this occasion also the TRIM magnets are being re numbered The list of changes is given in Appendix 2 the new situation is shown in the layout optics drawing attached REVIEW of your past runs In order to allow users to find their way back to what was done to their beamline in the past the LOG files are now available on the web http nicewww cern ch sl eagroup eaframe html choose Logfiles and choose H8 For the information from previous years go to the end of the page Older Logfiles then make your choice A Modification History 13 H8 User Guide SPS Beam Line 23 May 2002 14 A Modification History H8 SPS Beam Line User Guide 23 May 2002 B Experimental Scalers Each experiment can provide feedback information into the NODAL system Table_xxx shows the present configuration Table 0 1 The configuration of the NODAL experimental scalers for the H8 beam line EXPT Barrack Experiment Index Comment 1 2 VD 0 N 0 01 Q 11 12 13 14 15 16 17 18 19 20 HNA262 HNA480 HNA468 HNA443 ATLAS H8A reserved ATLAS H8B reserved NA45 1 2 EA Crystal Experiment B Experimental Scalers 15 H8 User Guide SPS Beam Line 23 May 2002 16 B Experimental Scalers H8 SPS Beam Line User Guide 23 May 2002 C Beam Elements C 1 Trigger Counters Table C 1 BEATCH name Old Name lt 1999 Current Name Comment
11. am Line 23 May 2002 Type in your name when the program asks for it Wait until you get the message which confirms that you have access ACCESS GRANTED Then go to the door e g marked PPE158 make sure the lights ACCESS WITH KEY are flashing push the button with a key on it take the key for which the red diode lights up and use it to open the door and enter the zone PRESS THE DOOR HANDLE SLOWLY Every person entering the zone has to take a key and keep it with him your safety depends on this action When you come out of the zone you should put back the key and turn it into its normal position When the last person has finished check that nobody is left in the zone put back the last key push the red button marked END OF ACCESS do not forget otherwise you will not get beam and have to walk back to the door later and go back to your barrack At your beam terminal type e g ACCESS DOOR 158 BEAM ON type in your name you are responsible for persons left in the zone and wait till beam comes back The SL Radiation Safety Officer M Jonker has issued a memorandum describing the rules for access The main change is that 1 when more than 8 persons need to enter the experimental area the experimental team should change the zone to FREE access mode 2 only the CRN operators can change from FREE to KEY access mode Such a change can only be made if the zone is being searched following a prescribed search proc
12. ation for very low Beam Energies 21 E 1 The low energy wiggle 21 Table Of Contents H8 User Guide SPS Beam Line 23 May 2002 iv Table Of Contents H8 User Guide SPS Beam Line 23 May 2002 List of Tables Table 0 1 p 15 The configuration of the NODAL experimental scalers for the H8 beam line Table C 1 p 17 Table C 2 p 17 Table D 1 p 19 Table E 1 p 21 List of Tables v H8 User Guide SPS Beam Line 23 May 2002 List of Figures Fig E 1 p 22 The Low Energy Wiggle vi List of Figures H8 User Guide SPS Beam Line 23 May 2002 1 The Layout of the H8 Beam The H8 beam is a secondary particle beam that provides hadrons electrons or muons of ener gies between 10 and 400 GeV c as well as 450 GeV c primary protons and up to 400 GeV c per charge 32 8 TeV primary Pb ions The H8 beam is a part of the SPS North Area EHN1 building 887 This note gives a short introduction to the basic elements of the H8 beam For more detailed information the users are referred to one of the SL EA liaison physicists A 450 GeV c primary proton beam is extracted from the SPS towards the North Areas split into three beams of which one is directed onto the T4 primary target Typical intensities of this primary beam are a few 1012 protons per burst For proper operation of the beams the symmetry on the T4 target should be at least 65 with a small a indicating that the angular asymmetry is included in the value
13. ce to the H8B zone Their rates can be measured by TUNE MEAS TRIG 5 USE Norm 2 nr of bursts Note that the scintillator can be moved in to and out of the beam with TUNE MEAS USE or TUNE MEAS OUT EXPT Experimental scalers do not count any of our detectors but rather yours In your barrack there is a panel with four plugs In each of the four you can provide a standard NIM signal that is counted over each burst and read into the SPS com puter system These counts are displayed by TUNE MEAS EXPT scaler norm 2 nr bursts where the scaler number depends on the barrack ask your EA physicist The TRIG and EXPT counters are very useful in beam tuning Steering can be somewhat helped by the SCAN procedure for example TUNE SCAN EXPT 3 norm 2 TRIM 8 50 50 20 varies the Trim 8 current from 50 to 50 Amps in steps of 20 Amps one step per burst meas ure the count in EXPT 3 you know what that count means normalise it to NORM 2 and dis play the ratio of EXPT 3 and NORM 2 versus the TRIM 4 current at the end This technique of using a normalisation counter helps to be less sensitive to fluctuations in the SPS itself The SCAN procedure allows to choose the optimum current for e g TRIM 8 You can set this current by TUNE SET TRIM 8 current and eventually save it into the beam file by FILES WRITE H8 nn comment TRIM 8 current where the comment is a text of up to 30 characters
14. displayed This number as well as the T4 intensity can be read from the so called PAGE 1 TV screens in the electronics huts and control rooms From the T4 target three second ary beams are derived the PO beam to ECN3 the H8 and the H6 beams The momenta and po larities of the three beams are strongly correlated For example if the PO beam runs at 450 GeV c the standard condition the H8 beam can run at any negative polarity 10 to 400 GeV c or at positive polarities up to 180 GeV The H6 beam always runs at the polarity of the H8 beam and typically up to 50 of the momentum chosen in H8 Any of these front end changes of the beams should be done by an SL EA liaison physicist or a CRN operator and only during work ing hours 1 1 Different modes of H8 operation There are five distinct modes of operating the H8 beam 1 as a 450 GeV proton micro beam see appendix 1 2 in the high resolution mode 3 in the high transmission mode 4 in the filter mode testbeam mode also used to produce tertiary beams 5 as a heavy ion beam not discussed in this note For a user asking for different particles energies the filter mode is the optics used to calculate the beam files it provides a large range in energies from 10 to 300 GeV c and several possibili ties to create tertiary beams see below For a low intensity 400 GeV c hadron beam the high resolution mode has to be used because of lack of magnet strength in some rel
15. edure The search is made by the CRN operator or by an authorised person of the experiment whose name will be noted by the CRN operator 3 Search authorisaton is granted by the RSO of SL and or the RSO of PPE to a limited number of persons from the experiment which are designated by their GLIMOS All experimental areas have been equipped with a timer If a door on key access stays open for longer than 1 minute the zone is automatically set on FREE access FREE access can also be re quested from your beam terminal via ACCESS DOOR 158 FREE In both cases a search of the area is needed to go from FREE access to access WITH KEY see above new in 1997 SEARCH done by 1 CRN operator 1 Physicist of the experiment After an access itis wise to check that all magnet currents are OK by typing STATUS MAGNETS If the magnets do not switch on properly then try ACCESS BEAM ON again or try to set them to their BIM 0 value by TUNE SET If the problem persists call the CRN operators Important In the door itself next to the handle there is a round pastille with a dim red light in it which should be pushed in emergency cases only Whenever this button is pushed it re quires an operator to come over and reset the emergency stop manually This may cause signifi cant loss of beam time in particular because the operators are often working on another problem elsewhere H8 SPS Beam Line User Guide 23 May 2002
16. evant quadrupoles Q7 Note that at positive polarity the 400 GeV c beam consists mainly of protons whereas at negative polarity it contains mainly pions Information on beam composition in secondary beams can be found in the following reports 1 H A Atherton et al CERN Yellow Report No 80 07 2 G Ambrosini et al CERN EP 99 019 Europhys Journal C H8 User Guide SPS Beam Line 23 May 2002 1 2 Beams available in H8 If the PO beam is off the H8 beam can run in the 450 GeV c micro beam mode see below This mode implies significant hardware changes to the beamline and switching to and from the micro beam requires time and a stop of the whole North Area for several hours If the H8 beam runs as a secondary hadron or electron beam in the filter mode a further TAR GET can be introduced into the beam to produce tertiary beams of lower energy Typically this is done when H8 runs at e g 200 GeV c and tertiary beams then range from 10 to 150 GeV c for pions 10 and 20 GeV c tertiary beams are marginal This mode of operation allows an easy change of beam momentum which can be done by the H8 users from their beam control terminal simply by loading a different file 1 3 Experimental areas in H8 Like all other beams in EHN1 we distinguish experimental areas at present only NA45 in H8 and test zones Since 1997 the zone H8A is used by ATLAS inner detectors and TileCal hadron ic calorimeter H8B by ATLAS EMB liqu
17. id argon electromagnetic barrel calorimeter and AT LAS muon detectors There are two beam control terminals for ATLAS the H8A terminal in the common ATLAS control room on the ground floor and the H8B terminal in the control room of the barrel em calorimeter upstairs HNA468 From the point of view of emergency stops inter com beam index etc the two zones H8A B are treated as a single one From time to time some test beam activities with bent crystals take place in an area near door 128 not a formal test zone 2 The Control Tree The user wants to select the energy and polarity of the particles in his beam to steer the parti cles into a selected part of the detector and to adjust the spot size focussing He needs to choose the type of beam particles control the beam intensity and eventually to stop the beam and get access to his experimental zone He will use the beam instrumentation to check certain properties of the beam Finally he needs to monitor that all the equipment in the beam is func tioning correctly All these tasks can be performed from the beam terminal an X terminal connected to a cluster of HP UNIX computers running the NODAL system From this terminal the user controls the beam and related equipment through the so called TREE program invoked by the command RUN TREE or if necessary RUN lt index gt TREE where the index is 217 for NA45 and 205 for the ATLAS test zones From then onward the user just f
18. ing at RD21 use Q17 Q21 and Q18 Note that in order to transport the microbeam from a focus at NA45 to a focus at ATLAS Q17 had to be strengthened a third quadrupole was added acting as a third Q17 this quad is called Q21 and is used only in microbeam mode 11 H8 User Guide SPS Beam Line 23 May 2002 12 H8 User Guide SPS Beam Line 23 May 2002 A Modification History A 1 A 2 H8 Beam updates during 2000 A new collimator C7 has been installed to double up C9 this is used to separate hadrons from electrons positrons at high energies closing C7 together with C9 should e g reduce the hadron contamination in the 180 GeV positron beam as well as the 200 and 300 GeV electron beams A second Threshold Cerenkov counter XCET has been installed in zone 158 i e just up stream of ATLAS This is a standard beam instrument see DETECTOR THRESHOLD and replaces the counter so far provided by ATLAS Tiles This counter is used with two TRIG scintillation counters TRIG5 TRIG6 A new lead glass calorimeter KEMC allowing to study the beam composition is in stalled just after the second Cerenkov counter This instrument is used by experts only e g by the CRN operators on request of the users The XEMC is operated in coincidence with a small TRIG counter 2x2 cm2 called TRIG7 Use the option TUNE MEAS CALO to use the XEMC Following the installation of new material see above the TRI
19. is open Check in particular after MD s or technical stops 5 Call the CRN operators Intercom Tel 75566 or NATEL 160137 if all this fails 10 Special Beams 10 1 H8 operation as 450 GeV microbeam The H8 beam can be operated with 450 GeV protons from T4 in the so called microbeam mode Historically the microbeam was developed by H Atherton to satisfy a request for a very small beam spot at the NA34 experiment it was used in its original version with two sets of vertical horizontal micro collimators called C12 C13 and C14 C15 In recent years a simpler version of the microbeam was used only the first set of micro collima tors C12 C13 is operational and the beam spots are larger however the users of the 450 GeV beam typically NA12 NA45 and RD21 seemed to be happy with it For the bent crystal exper iments which are done at the place of the former second micro collimator station i e ata posi tion 414 m from T4 the beam optics is modified such as to have a horizontally parallel vertically focussed beam at the crystal 10 1 1 Interlock conditions The different options of the H8 beam normal secondary beam microbeam ion beam have dif ferent interlock conditions which can be found in Fig 1 obtained on DICO from the tree via 10 H8 User Guide SPS Beam Line 23 May 2002 EA BEAM SETUP It is important to note that for the microbeam mode of H8 only the condi tion TAX 6 RANGE SMALL is an interlock
20. ly perform reasonably for beam rates above 1000 particles per burst These profiles are obtained by typing TUNE MEAS MWPC PROFILE Often the first profiles look strange repeat profiles because HV adjustment in the chambers is done automatically with every profile Scintillation counter filaments of 0 2 mm widths moving through the beam at 1 step per burst which provide horizontal and vertical profiles in particular in sec ondary beams To use a FISC type TUNE MEAS FISC PROFILE fisc number norm 2 start mm end mm stepsize mm FISCs 1 2 and 5 to 10 are FASTFiscs i e the beam profile can be obtained in one spill In order to normalise the profile to the beam intensity during the spill a so called NORMFisc is automatically placed in the beam in H8 this is FISC4 To use a FISC in this mode type TUNE MEAS FISC PROFILE fisc number NEW return start mm end mm stepsize mm Note that the max number of points in a spill is 80 H8 User Guide SPS Beam Line 23 May 2002 TRIG Scintillation counters Trig 1 counts the rate between the two main BENDs Trig 2 is located before the last horizontal BENDs 5 6 Trig 3 and Trig 4 are used as trigger counters for the XCET 1 threshold Cerenkov counter see below Trig 5 and Trig 6 are used as trigger counters for the XCET 2 threshold Cerenkov counter TRIG6 also counts the rate just upstream of the H8A experiments and TRIG8 at the entran
21. nged without additional thinking E 1 The low energy wiggle The main vertical bending magnets in H8 are B1 B2 41 mr 6 MBN magnets near the end of TCC2 target area and B3 B4 41 mr at the top of TT82 A general problem at low energy is the stability and precision of low currents in the recitifiers At high energy two rectifiers are needed for B1 B2 as well as B3 B4 At low energy higher sta bility and precision is obtained if one works only with one out of the two rectifiers i e with double the currents In order to obtain a good beam transfer the bending magnets have been re cabled and the new layout is as follows E Operation for very low Beam Energies 21 H8 User Guide SPS Beam Line 23 May 2002 B3 B4 B4 B3 B3 B4 Bl B2 B2 S 8 o So Y n lt lt distance from first B1 11 32 m 18 13 m 23 79 m 29 45 m Figure E 1 The Low Energy Wiggle In the low energy wiggling mode B1 B3 0 and B2 B4 are used at twice the current This im plies that the effective bending point is moved 0 75 meters downstream As the total bending angle is 41 mr we get a vertical offset of the beam of 0 75 41 30 mm at the level of B1 B2 The magnification i e the effect of the beam optics being 1 at collimator C6 implies that the verti cal offset of the beam at C6 should be 30 mm 22 E Operation for very low Beam Energies H8 User Guide SPS Beam Line 23 May 2002
22. ns by loading a file from the tree FILES LOAD H8 nn and then answering the questions In particular one has the option to change only magnets only collimators or both Magnet current changes are fast collimator changes may be much slower This command copies the values of file H8 nn into BIM O and sets the proper magnet currents and or collimator positions NOTE that the target and absorber are NOT changed when loading a file WARNING Changing from a tertiary beam typically with wide open collimator settings to a secondary beam one should first load only the collimators then the magnets Otherwise dur ing some bursts very high intensities might be present in your beam line It is wise to check that the equipment has responded correctly to the requested changes by typ ing STATUS CHECK or STATUS MAGNETS and STATUS COLL thus verifying that the currents positions read correspond within tolerances to the currents positions in BIM 0 Tolerable deviations are 0 2 0 3 Amps for BENDS and QUADS 0 5 Amps for TRIMS 0 2 mm for collimators In case of problems try once more to load the file If the problem still persists call the CRN operator using the intercom CRN or phone 75566 NA TEL 160137 The EA liaison physicist can do nothing for you in this case In case of doubts about your beam particles or to check other parts of your beam please check STATUS GENERAL which will give you a full account on your TARGET ABSORBER
23. ollows the menus offered by the control tree Note that the NODAL system traditionally only accepted upper case In case you get lost or stuck you can leave the control tree by typing CTRL_C You can then enter the tree again by RUN TREF In case of mis typing you should use backspace In emergency cases only switch terminal OFF ON H8 User Guide SPS Beam Line 23 May 2002 Additional windows can be obtained to work or count in parallel by selecting in the dark area of your screen local X terminal with the mouse The window will open in unix mode with the prompt eanorth you have to type NODAL to continue 3 Beam Files Normally each user has a number of different beam energies and corresponding beam intensi ties at which he wants to run his experiment These sets of conditions are described by Beam Files In each index 205 or 217 there are 10 read only beam files and up to 99 beam files for use by the experiments The EA files are called H8 A to H8 J and the user files are numbered H8 1 to H8 99 These files contain all magnet and collimator settings A list of available files is obtained by FILES LIST Usually beam files are prepared by or after discussion with the responsible EA liaison physicist although experienced users will sometimes change files themselves The actual conditions in use at any given time are described by another beam file called the BIM 0 file The user can select new conditio
24. purification can be obtained by entering an ABSORBER 4 8 or 18 mm of Pb into the beam Choose the appropriate file and use POLY or Cu as a TARGET Momentum selection as above use the ABSORBER to kill the electrons in the tertiary beam Note that the Cu target generally gives less intense but more clean tertiary hadron beams Mixed beam Do you really want it You get it by not applying the prescriptions above i e choose a tertiary hadron beam and do not remove electrons by lead sheets Muons Choose a secondary hadron beam file and close collimator C9 and C10 asymmetri cally i e setting the jaws to 45 and 46 mm respectively The muon momen tum is selected by BEND5 and BEND6 For higher muon fluxes open all collimators upstream of C9 The TARGET can be changed by TUNE SPECIAL MODE TARGET and the ABSORBER by TUNE SPECIAL MODE ABSORBER and the situation of the TRIG counters and MWPCs can be observed or changed by TUNE MEAS TRIG TUNE MEAS MWPC MOVE Note however that in general a TRIG counter is always mounted on one support with a MWPC e g TRIG1 with MWPC1 2 7 Access to your zone Frequently you will need access to your zone in order to modify adjust move or repair your ap paratus This is done through the command ACCESS DOOR 138 OPEN for the NA45 zone ACCESS DOOR 158 OPEN for the H8A test zone ACCESS DOOR 168 OPEN for the H8B test zone H8 User Guide SPS Be
25. roportional to the distance from the TRIM When starting a run with a given beam file a TRIM scan should be made to make sure you have the correct steering The currents in these magnets can be set using e g TUNE SET TRIM 8 current These changes are not saved in the files except the BIM O file for the present status 5 Beam Intensity and Momentum Spread The beam intensity for a secondary beam is normally controlled by three collimators namely C3 Momentum defining collimator vertical C5 and C6 X and Y acceptance collimators The momentum defining collimator C3 defines the momentum of the particles transported to your detector The momentum byte Ap p is proportional to the opening of the collimator A gap of 3 mm gives a Ap p of approximately 0 1 More accurately the general expression to calculate the full width momentum spread is RE Ap_ C3 Co ue 5 1 P 27 where C3 and C9 are the full width opening of these collimators in mm 27 mm is the verti cal momentum dispersion of the beam at C3 compared to C9 This expression holds for a terti ary beam in all cases while for a secondary beam C9 is often more open than the beam image and should be replaced by 2 mm the T4 target thickness i e the source size of a high energy secondary beam in which case C3 usually dominates the resulting Ap p H8 User Guide SPS Beam Line 23 May 2002 Decreasing the opening of C5 and C6 results in a non linear red
26. uction of rate It is not related to the momentum band of the beam The collimators are controlled by e g TUNE SET COLL 3 JAWS 5 5 or TUNE SET COLL 5 SLIT 24 Note that depending on momentum byte requirements it may be more advantageous to close C3 than C5 6 or conversely to open C5 6 rather than C3 Sometimes it turns out not to be possible to reduce the rate sufficiently by closing C5 and C6 Other collimators have to be closed in those cases material can be put in the beam and if neces sary the first 3 quadrupoles can be set to zero 6 The type of particles in your beam Overview of your present beam In order to get rapid information on the beam you are currently using you may type STATUS MODE You will get the status of TARGET ABSORBER relevant collimators etc Several options exist for the type of particles in your beam ions not treated here 450 GeV protons These are selected at O degrees from the production target and transported to a set of micro collimators C12 and C13 between the two main vertical BENDs At these microcollimators a new source of the beam is defined intensity reduced by orders of magnitude Setting up and most of the operations of the micro beam are done by the SL EA physicist see the Appendix Pure electrons secondary beams These are obtained by loading the appropriate file and by assuring that the dangerous material target absorber and TRIG counters beam dump
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