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 construction endplates, “boxes” practical: install, survey, calibrate, repair –planar chambers –identical cells –triangular boxes –self-supporting Planar chambers “triangular” shape Dave Kashy’s talk Error Budget: individual sources < 25  m

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 ionization electrons) 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 stainless steel (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! R3 cell

12. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Design based on “slanted” endplates endplates minimize dead area 8 mm

13. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Stiffening Frame: Extra Thickness where it Counts 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 Tracking: Momentum Resolution fractional momentum resolution vs. momentum different configurations

18. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Forward Tracking: Momentum Resolution 250  350  m fractional momentum resolution vs. momentum

19. 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 –generate tracks with background; reconstruct tracks the best method Latifa Elouadrhiri’s talk

20. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Improved Rate Capability: relative to 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 Tracking will be efficient at 10 35 /cm 2 /s Performance: Drift Chamber Rate Capability Latifa Elouadrhiri’s talk

21. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Specifications:Design Features: L = 10 35 /cm 2 /s - high efficiency with large backgrounds small cells six 6-layer superlayers 30  m wires  p/p < 1%  mrad 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 structure Summary : specifications  design concepts

22. 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

23. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer Features that require most design work Chamber “boxes” - especially 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

24. 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 –is wire sensitive near feedthrough? Prototyping Plans: Drift Chambers Stephen Bueltman’s talk

25. 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; refine procedures construction: many details We are ready for the challenge ! Latifa George Chris Dave Stephen