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Charged Particle Tracking for CLAS12

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  1. Charged Particle Tracking for CLAS12 Physics a tracking requirements a detector specifications Detector Design Barrel Vertex Tracker (BVT) Forward Vertex Tracker (FVT) Drift Chambers (DC) Optimizing the Design BVT (mixed Si/MM?) FVT (stereo angle?) Basic overview Design options Simulation results Technology reviews Maximizing efficiency and resolution at high rates Key decision points CLAS12 Detector Review

  2. Tracking: physics a design spec’s Experiment Characteristics • electron beam • small cross-sections(exclusive reactions, Q2-dep.) • measurehadronic state • establish exclusivity (missing mass) • other cuts: co-planarity, etc. • forward-going particles • small laboratory angles • broad coverage in center-of-mass CLAS12 Detector Review

  3. Physics goals ageneral design spec’s CLAS12 Detector Review

  4. Tracking Specifications Summary CLAS12 Detector Review

  5. CLAS12 tracking: ca. 2008 torus solenoid Si tracker reg. 1 reg. 2 DC’s reg. 3 CLAS12 Detector Review

  6. Silicon trackers and drift chambers • Central tracker: • single-sided Si strips • 150 mm pitch • barrel: 4 x 2, graded 3o stereo • fwd: 3 x 2, +/- 12o stereo • DC’s: same concept • as present chambers • 6 sectors, 3 regions • 2 super-layers/region • +/- 6o stereo • regions at ~ 2, 3, 4 m. • 112 wires/layer (24192) • 250 mm resolution CLAS12 Detector Review

  7. BST & FVT Assembly • Silicon vertex tracker reviewed on April 2: • design meets physics requirements • design is technically feasible • recommend we do the following: • develop alignment specifications • develop an operational plan • develop a grounding scheme • no further discussion of Si tracker in this review; unless requested CLAS12 Detector Review

  8. Central vertex tracking • Central or “barrel” vertex detector (BVT) • mixed: inner - Silicon, outer – Micromegas • Silicon: • better position resolution • but, more multiple scattering • and, very small stereo angle • all-Si design good for dp/p, df; bad for dq, dz CLAS12 Detector Review

  9. Résultats • 3 dispositifs ont été étudiés: • - 4x2 SI ( = 1.5°, et  = 43 m) • 4x2 MM ( = 0 et 90°) • 2x2 SI+ 3x2 MM pT/pT  SI(+MM)   MM

  10. Résultats - 2   SI(+MM) z  MM

  11. Silicon + Micromegas ? • simulations show mixed solution best, but • can Micromegas work with a cylindrical geometry? • can Micromegas work in a high, transverse B-field ? • Review the technology CLAS12 Detector Review

  12. Review of Micromegas Tracking Detectors for CLAS12 – May 7, 2009 • Reviewers: Madhu Dixit, Mac Mestayer • Presentations covered the following topics: • detector overview: layers, strip pitch, segmentation for central & forward regions • fabrication overview: principles and prototype testing of “bulk” technology • detector simulation: GARFIELD results on drift, diffusion, gain • tracking simulation: particle backgrounds, tracking efficiency and resolution • acceptance and quality assurance: methods to validate component performance • prototype testing: measurements of position resolution, Lorentz angle, gain times transmission and tracking efficiency for minimum-ionizing tracks; including tests of curved detectors and tests in magnetic fields • electronics: overview of requirements for charge and time measurements; options for an integrated system: amplification/discrimination/digitization/ readout. • Impressive new pioneering work on curved Micromegas technology and operation in transverse magnetic fields

  13. Resolution of the charges: • The simulated performance for resolution, solid angle coverage and efficiency meet or exceed CLAS12 requirements. • The design is based upon existing technology, simulated at both the signal and track-finding level with key parameters verified by prototype tests. The simulations are consistent with the test results. • The conceptual plans for detector integration (including safety systems) are consistent with the overall CLAS12 detector layout. • The schedule and allocated manpower seem reasonable. • The group is competent; recognized world leaders in this technology. We are confident that the group can successfully design and build the proposed tracking detectors for CLAS12.

  14. Optimizing the BST design • what’s best mixture of Si. vs. MM? 2 X 3 ? • integrated vs. independent mech. structure • best combination E field/ drift gap? • stereo angle: • smaller than 90 deg.? • fewer ‘ghost’ hits, worse resolution • need flex-cable readout for “y” strips • mesh segmentation CLAS12 Detector Review

  15. Why do we need a forward vertex detector? • might find ‘stub’ tracks pointing to coils • might help with track-finding • vastly improves vertex information • improves other track parameters • better knowledge of Int(B X dl) CLAS12 Detector Review

  16. How will the FVT be used? • stand-alone tracker (no) • ‘seed’ for forward track (?) • vernier for dc-only track (yes) • need good background rejection • Requirements • Efficiency • prob. of >1 hit in ‘matching circle’ < 20% • Resolution • ~100 micron spatial resolution CLAS12 Detector Review

  17. Presentforwardtracker (DC, FST) • 6 independentsectors • 3 chambers (‘regions’) per sector • 2 six-layer superlayers (+/- 6 °) • plane tilted by 25° wrt the beam axis • acceptance: 5°40° DC Striplayout: • 3x2 layers • trapezoidal tiles • 12° stereo angle • acceptance: 5°35° FST Simulation & Reconstruction 10/30/2008 S.Procureur

  18. Torus magnetic field • ∫B∙dl ~ 3 T-m • highest field for forward tracks B (tesla) Scattering angle (degrees) CLAS12 Detector Review

  19. Match DC track to FST hit 98% of DC tracks extrapolate within +/- 1 cm. So, how many background hits in the ‘circle of confusion’? CLAS12 Detector Review

  20. Resolutionswith DC+FST (electronsat = 15°, nowfrom GEMC!): 20 times better 5 times better FST greatlyimproves the vertex resolution, ,  and p Simulation & Reconstruction 10/30/2008 S.Procureur

  21. DC+FST – resolutionwith protons (protons at  = 15°): 3-4 times better 8-10 times better Much better vertex resolution with FST (and  resolution at high p)

  22. Change FST to Micromegas? • Difficulties with FST • massive cooling structure in live area • no cooling in live area for Micromegas • dead area around each trapezoidal sensor • very small dead areas for Micromegas • hard to deal with high rate at small radius • Difficulties with Micromegas • parallel E and B-fields • very little charge spreading • charged track hits look like x-ray hits CLAS12 Detector Review

  23. Optimize FST parameters? • optimum stereo angle? - more choice • large angle gives better theta resolution • but, also gives more fake strip matches • mixed strip and pixel segmentation • want fewer strip crossings at small radius • ghost hits will appear at larger radius • can we cover the full azimuth? • what is the mesh segmentation? radial? CLAS12 Detector Review

  24. Key Decision Points • BST • how many layers of Si? …MM? • 2 – 3? 3 – 3? • unified or independent structure ? • internal accuracy vs. ease of installation/repair • layout details: stereo angle, mesh segmentation • study two-layer ‘punch-through’ background • sensor design: drift gap, field strength • reduce sparking rate CLAS12 Detector Review

  25. Key Decision Points • FST • Super-layer structure okay? • 3 units, each u – v • Background is very radially-dependent • want radial segmentation? • if so, how do we get signals out? • What is the optimum stereo angle? • balance dq vs. ghost hits • Can we cover the full azimuth? CLAS12 Detector Review

  26. CLAS12 Tracking: Summary • Si + MM provides excellent resolution in central region: better than Si or MM alone • FVT: better vertex than DC12 alone • Si disk design works well, but • MM design offers more readout flexibility • finer segmentation in ‘hot’ region • full azimuthal coverage • Micromegas has a major role in CLAS12 CLAS12 Detector Review

  27. Backup slides on DC12 CLAS12 Detector Review

  28. Physics goal Physics spec. Design feature CLAS12 Detector Review

  29. Superlayer Wire LayoutStaggered “Brick-Wall” Hexagonal field field sense field field sense . . . . . sense field field sense field field coloredcircles represent drift distances 6 sense layers, 2 guard layers, 14 field layers: 1 superlayer CLAS12 Detector Review

  30. Rationale for Design Decisions CLAS12 Detector Review

  31. Drift Velocity Calculation 20 mm wire 2325 V 88:12 AR:CO2 30 mm wire 2475 V 92:08 AR:CO2 same gain 58% faster - and more linear ! use 30 mm wire! CLAS12 Detector Review

  32. Endplates: many precise holes Number of Holes 4925 feedthrough holes 12 survey 3 datum & alignment 28 bolt & attachment 1.7 m CLAS12 Detector Review

  33. Endplate Details 0.200 mm true position a “50 mm” CLAS12 Detector Review

  34. Endplates fit into Frames • Receive endplates • - inspect • - measure hole positions • - clean • Receive frames • - inspect and clean • pre-bow endplate and frames • bolt and glue into frames CLAS12 Detector Review

  35. Chamber Ready to String Box Assembled -endplates attached -attachment brackets affixed Next --- - mount on stringing fixture - insert feedthroughs - install survey points - string wires - attach circuit boards - QA/QC CLAS12 Detector Review

  36. CLAS12 Stringing Fixture CLAS12 Detector Review

  37. Parts: wire a circuit board signal routing: wires a pre-amp conductive rubber circuit board crimp pin feedthrough endplate circuit board wire CLAS12 Detector Review

  38. Stringing wires between “slanted” endplates “gravity” stringing wires: 9 cm - 4 m long wires strung individually wires attached by crimping wires positioned by “trumpet” endplates CLAS12 Detector Review

  39. Steps in Stringing CLAS12 Detector Review

  40. Installing Pre-tensioning Wires Pre-tensioning - before we start stringing - use springs on guard wires - gradual release of tension CLAS12 Detector Review

  41. Stringing the Chamber CLAS12 Detector Review

  42. Installing Pre-amplifier Boards On-board pre-amplifier boards and high-voltage distribution boards are installed after wires are strung. CLAS12 Detector Review

  43. Electronics: Chamber a TDC 75 ft. cable Post-amp x 10 - x 30 30 mV disc. drift chamber Pre-amp 2 mV/mA 1 mA 2 - 3 electrons re-use post-amps, TDC’s TDC’s Lecroy 1877 new circuit boards based on old SIP’s CLAS12 Detector Review

  44. Model of Torus and Chambers • very useful: • installation • cabling • access CLAS12 Detector Review

  45. Tight-packing of Cables, Connectors CAD layouts verified on a model: tight spacing dictated by requirement of 50% f-coverage at 5o multi-layer composite endplate !! CLAS12 Detector Review

  46. Installation and mounting scheme Linkage system allows quick and accurate installation Positioning accuracy reproducible to 25 mm CLAS12 Detector Review

  47. ~1/2 time for stringing ~2 yrs./ 6 chambers Schedule: Stringing the Chambers CLAS12 Detector Review

  48. Safety and Quality Assurance CLAS12 Detector Review

  49. Project Overview & Responsibilities • Oversight: Jefferson Lab • Prototyping • full-sized Reg. 1 prototype: Jlab, ODU • beam tests: Jlab, ISU • Design • Region 1 & 2: JLab • Region 3: Idaho State • Build, String & Commission • Reg. 1 - Idaho State • Reg. 2 - ODU • Reg. 3 - JLab CLAS12 Detector Review

  50. CLAS Drift Chambers : History • Operating successfully for ~10 years …. A photo of the first “Reg. 3” chamber moving into Hall B CLAS12 Detector Review