1. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Drift Chambers for CLAS12 - Mac Mestayer Context: how does it fit within CLAS12 ? Specifications: physics  tracking specs.  design concepts  design Design concepts: –‘regions’  superlayers  layers  cells –‘umbrella’ design: minimize  dead – planar layout, triangular boxes: accuracy Simulations, Prototyping Issues Planned improvements and conclusion

2. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Toroidal magnet ∫ B dl ~ 3 T-m 6 “sectors” between coils 3 “regions” of DC 1 - 2 - 3 ! 2 superlayers/region 6 layers/superlayer 112 wires/layer 24192 sense wires Drift Chambers for CLAS12

3. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer electron beam –shift in  ~ 1 mrad  2.5% shift in cross-sections small cross-sections –L = 10 35 /cm 2 /sec measure hadronic state (esp. excl. reactions) –reject extra particles (missing mass) |dp| ~ 50 MeV/c, sin  p &  p ~ 20 MeV/c –other cuts: co-planarity, etc.  ~5 mrad forward-going particles –5 o minimum lab angle broad coverage in center-of-mass –minimize dead area Tracking: physics  design spec’s

4. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Goals:Specifications: measure cross-section accurately  ~ 1 mrad dp/p < 1% select an exclusive reaction; e.g. only one missing pion  p <.05 GeV/c  p <.02 GeV/c sin   p <.02 GeV/c small cross-sections L = 10 35 /cm 2 /s high efficiency good acceptance  ~ 50% at 5 o Design Specification

5. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer measure charged tracks (5 o – 40 o ) CLAS12 Drift Chambers DC’s: same concept as present chambers - but planar hexagonal cells 6 sectors, 3 regions 2 super-layers/region 6 layers/super-layer 112 wires/layer (24192) angled endplates on-board pre-amps

6. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Torus magnetic field ∫B∙dl ~ 3 T-m highest field for forward tracks

7. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Drift chamber layout Six sectors: Region 1 Design Principles: –large solid angle (minimize dead area) –accurate (250  m position accuracy) –practical (install, survey, calibrate) –cost effective ~2m central SVT and target

8. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer accurate (250 mm position accuracy) practical (how to: install, survey, calibrate, repair) planar chambers –identical cells –triangular boxes –self-supporting design Planar chambers “triangular” shape Dave Kashy’s talk

9. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Wire Layout Staggered “Brick-Wall” Hexagonal hit wires shown in yellow circles represent drift distances field sense field sense. sense field sense field 6 sense layers, 2 guard layers, 14 field layers: 1 superlayer

10. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer DC design details gas: Ar/CO 2 (92:08) gain ~ 5 ∙ 10 4 (sensitive to 2 - 3 electrons; very efficient) drift velocity ~ 25 to 50  m/ns time windows: ~ 150, 200 - 500, 500 ns material choices: –wire: 30  m W, 140  m Al, 140  m SS –endplates: Aluminum, Stesalit, Aluminum –Noryl plastic feed-throughs, SS insert –gas system: SS, small sections of Nylon, Al-Mylar –FR4 circuit boards

11. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Drift Velocity Calculation 20  m wire 2325 V 88:12 AR:CO 2 30  m wire 2475 V 92:08 AR:CO 2 same gain 58% faster - and more linear ! use 30  m wire!

12. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Design based on “slanted” endplates endplates minimize dead area

13. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer minimize dead area stiffening frame

14. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer large solid angle (minimize dead area) –small aspect ratio pre-amp boards –extend in z to maximize azimuthal coverage –flanges stiffen frame; do not extend dead area Circuit Board Placement

15. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer 1  A 2 - 3 electrons Pre-amp 2 mV/  A Post-amp x 10 - x 30 30 mV disc. drift chamber 75 ft. cable TDC’s Lecroy 1877 new circuit boards Chris Cuevas’ talk Electronics: chamber  TDC

16. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracker: Expected Resolution dp/p, d , d , dx - plotted versus p - at 35 o 1% 0.5 mrad 100 microns dominated by multiple scattering

17. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracker: Momentum Resolution fractional momentum resolution vs. momentum different configurations

18. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Performance: efficiencies; resolutions Rate studies: –extrapolation from present CLAS decrease solid angle, time window, thickness of DC cells –estimates of layer occupancy present studies show efficiency fall-off about 4% occupancy estimates don’t require track reconstruction –estimates of track efficiency and fakes input random background with correct average occupancy use a cut-based track finder –generate tracks with background; reconstruct tracks the gold standard Latifa Elouadrhiri’s talk

19. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Rate Capability: 10 - 30 times “CLAS” –factor of 3: one cell’s angular size 1/3 as large 5 - 40 o instead of 10 - 120 o, 70% as many wires –factor of 1.5: smaller time window thicker wire, higher field, faster gas –factor of ~ 5: better shielding larger solenoid, better absorber Performance: Drift Chamber Rate Capability Latifa Elouadrhiri’s talk

20. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Specifications:Fwd.Design Features: L = 10 35 /cm 2 /s - high efficiency with large backgrounds small cells six 6-layer superlayers 30  m wires good  p/p,  planar chambers identical cells (easy to calibrate) ~linear drift velocity +/- 6 o stereo angle good acceptanceflanged frame low wire tensions  ~ 50% of 2  at 5 o reliabilityself-supporting design Summary : spec’s  design concepts

21. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Drift Chamber Design Decisions 6x6 layersrobust track-finding +/- 6 o stereo better  resolution than CLAS planar; self-supportingidentical cells, easy to calibrate, survey, repair 112 wires/layerenough for 10 35 operation 30  m sense wire 92/08 Ar:CO 2 faster, linear distance-vs-time, strong, more reliable stringing low wire tensionthinner endplates on-chamber amplifiersgood signal/noise re-use hv, lv, ADB, TDClots of spares; cost savings; better segmentation

22. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Features that require most design work Chamber “boxes” - esp. attachments, relative alignments, ease of installation and removal Region 2 attachment method; –specifications for torus On-chamber PCB’s - small space Region 3: outer “skin”, inner posts Cable routing - mundane but important Design Plans: Drift Chambers

23. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer New features that require prototypes smaller cells, thicker wire, less CO 2 –higher voltages: leakage current, cathode emission –higher electro-static forces –less quenching pre-bowed endplate –accuracy of wire placement all-plastic feedthroughs –where is wire sensitive? Prototyping Plans: Drift Chambers Stephen Bueltman’s talk

24. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Conclusions Design is a modest extrapolation –still a challenge to improve basic design: robust track-finding; good design resolution shielding: factor of ten; study permutations (mis-steering) gas, utilities, TDC’s fine; want better segmentation on-board electronics: good design; small footprint mechanical: minimize  dead ; design in tight specifications; practical considerations: easy to install, survey prototyping: discover flaws; tighten procedures construction: many details We are ready for the challenge ! Latifa George Chris Dave Stephen

25. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Remaining Simulation Work use FASTMC to estimate mass resolutions and other “physics” quantities choose reactions involving SVT, FSVT and DC’s; study effects of changing resolutions use GSIM12 to study tracking efficiency as a function of background study rate-dependence of efficiency use GEANT3, GEANT4 or DINREG study placement of shielding to minimize occupancy use RECSIS12 track-finding and selection choose optimum stereo angles ambiguities vs.  resolution

26. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracking Improvements: goals better momentum, angle resolution –more constant velocity, good mechanical tolerance higher luminosity operation –smaller cell solid angle, shorter time window good vertex resolution –Si strip detector more robust: easier to remove, fix –self-supporting design more constant calibration, easy to survey –planar chamber, smaller “boxes”

27. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Tracking Improvements: methods smaller “boxes” –easier to align, install –less expensive endplates larger diameter sense wire –stronger –higher E field, more constant drift velocity –shorter sensitive time fewer wires –better HV, LV segmentation faster gas (e.g. 92:8 AR:CO2) good engineering !

28. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Conclusion Design concepts are specified: –many small cells (good high-rate capability) –large solid angle (minimize dead area) –accurate (250 mm position accuracy) Full designs are underway –boxes, feedthroughs, pcb’s, cables, attachment points Simulations are underway –10 35 is doable –track resolutions will be adequate for experiments

29. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Project Overview & Responsibilities Design & Build –SVT: Los Alamos, UNH, Moscow State, JLab –Region 1: ODU –Region 2: JLab? –Region 3: Idaho State –MicroMegas: Saclay Miscellaneous prototyping –SVT and/or FSVT assembly frames –plastic vs. metal-tipped feedthroughs –alternative multiplexing boards Software –c++ - based tracking software Other –Magnet Mapper –Cost Estimates

30. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Drift Chamber Work List

31. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Drift Chamber Budget Procurement, expenses: 3.80 M$ Labor: 1.04 M$ Total: 4.83 M$

32. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracker Procurements/Expenses K$

33. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer CLAS12 / CLAS costs (not labor)

34. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracker: Labor man-weeks

35. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Broken wires –more extensive “shake-down” –better temperature control of hall (already implemented) Circuit board corrosion –go to copper, fiber-glass pcb’s –better humidity control (partially implemented) –finer segmentation (partially implemented) High current draw –stricter irradiation procedures (already implemented) –better humidity control (partially implemented) –more HV channels (planned for near-term) Operational Problems & Solutions