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 December 2, 2009 CLAS12 Detector Review

Tracking: physics a design spec’s Experiment Characteristics electron beam small cross-sections (exclusive reactions, Q2-dep.) measure hadronic state establish exclusivity (missing mass) other cuts: co-planarity, etc. forward-going particles small laboratory angles broad coverage in center-of-mass December 2, 2009 CLAS12 Detector Review

Physics goals a general design spec’s Specifications: measure flux-factor accurately q ~ 1 mrad dp/p < 1% select an exclusive reaction; e.g. only one missing pion dp < .05 GeV/c dq p < .02 GeV/c sinq df p < .02 GeV/c small cross-sections L = 1035/cm2/s high efficiency good acceptance Df ~ 50% at 5o December 2, 2009 CLAS12 Detector Review

Tracking Specifications Summary Fwd. Tracker Central Tracker Angular coverage 5o – 40o (50% f-coverage at 5o) 35o – 125o (> 90% f-coverage) Momentum resolution dp/p < 1% dp/p < 5% q Resolution 1 mrad 5 – 10 mrad f Resolution 1 mrad/sinq 5 mrad/sinq Luminosity 1035 cm-2 s-1 December 2, 2009 CLAS12 Detector Review

CLAS12 tracking: ca. 2008 torus solenoid Si tracker DC’s reg. 1 reg. 2 May 8, 2008 CLAS12 Detector Review

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 May 8, 2008 CLAS12 Detector Review

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 May 8, 2008 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

Résultats pT/pT  SI(+MM)   MM 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

Résultats - 2   SI(+MM) z  MM

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 December 2, 2009 CLAS12 Detector Review

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

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.

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 December 2, 2009 CLAS12 Detector Review

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) December 2, 2009 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

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

Torus magnetic field ∫B∙dl ~ 3 T-m highest field for forward tracks B (tesla) Scattering angle (degrees) December 2, 2009 CLAS12 Detector Review

Match DC track to FST hit 98% of DC tracks extrapolate within +/- 1 cm. So, how many background hits in the ‘circle of confusion’? December 2, 2009 CLAS12 Detector Review

Resolutions with DC+FST (electrons at  = 15°, now from GEMC!): 20 times better 5 times better FST greatly improves the vertex resolution, ,  and p Simulation & Reconstruction 10/30/2008 S.Procureur

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

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 December 2, 2009 CLAS12 Detector Review

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? December 2, 2009 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

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? December 2, 2009 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

Backup slides on DC12 December 2, 2009 CLAS12 Detector Review

Physics goal Physics spec. Design feature measure cross-section accurately q ~ 1 mrad dp/p < 1% planar chambers identical cells (easy to calibrate) 250 mm accuracy/layer select an exclusive reaction; e.g. only one missing pion dp < .05 GeV/c dq p < .02 GeV/c sinq df p < .02 GeV/c ~linear drift velocity +/- 6o stereo angle small cross-sections L = 1035/cm2/s high efficiency small cells six 6-layer superlayers 30 mm wires good acceptance Df ~ 50% of 2p at 5o pre-bowed frames low wire tensions self-supporting design December 2, 2009 CLAS12 Detector Review

Superlayer Wire Layout Staggered “Brick-Wall” Hexagonal field sense . colored circles represent drift distances 6 sense layers, 2 guard layers, 14 field layers: 1 superlayer December 2, 2009 CLAS12 Detector Review

Rationale for Design Decisions 6x6 layers robust track-finding +/- 6o stereo better f resolution than CLAS planar; self-supporting identical cells, easy to calibrate, survey, repair 112 wires/layer enough for 1035 operation 30 mm sense wire 92/08 Ar:CO2 faster, linear distance-vs-time, strong, more reliable stringing low wire tension thinner endplates on-chamber amplifiers good signal/noise re-use HV, LV, ADB, TDC lots of spares; cost savings; better segmentation Backup slide is recent design decisions. December 2, 2009 CLAS12 Detector Review

Drift Velocity Calculation use 30 mm wire! 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 ! GARFIELD calculations; backup is table of surface fields, gains for different configurations use 30 mm wire! December 2, 2009 CLAS12 Detector Review

Endplates: many precise holes Number of Holes 4925 feedthrough holes 12 survey 3 datum & alignment 28 bolt & attachment 1.7 m December 2, 2009 CLAS12 Detector Review

Endplate Details 0.200 mm true position a “50 mm” Backup is mechanical specifications document, including mechanical error budget December 2, 2009 CLAS12 Detector Review

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 Back-up slide showing pre-bowing December 2, 2009 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

CLAS12 Stringing Fixture Backup is recent photo December 2, 2009 CLAS12 Detector Review

Parts: wire a circuit board signal routing: wires a pre-amp conductive rubber circuit board crimp pin feedthrough endplate circuit board Backup is drawing of feedthrough designs wire December 2, 2009 CLAS12 Detector Review

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 Backup is photo of stringing December 2, 2009 CLAS12 Detector Review

Steps in Stringing December 2, 2009 CLAS12 Detector Review

Installing Pre-tensioning Wires - before we start stringing - use springs on guard wires - gradual release of tension December 2, 2009 CLAS12 Detector Review

Stringing the Chamber December 2, 2009 CLAS12 Detector Review

Installing Pre-amplifier Boards On-board pre-amplifier boards and high-voltage distribution boards are installed after wires are strung. December 2, 2009 CLAS12 Detector Review

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 backup is schematic of CP01 new circuit boards based on old SIP’s TDC’s Lecroy 1877 December 2, 2009 CLAS12 Detector Review

Model of Torus and Chambers very useful: installation cabling access December 2, 2009 CLAS12 Detector Review

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 !! December 2, 2009 CLAS12 Detector Review

Installation and mounting scheme Linkage system allows quick and accurate installation Positioning accuracy reproducible to 25 mm December 2, 2009 CLAS12 Detector Review

Schedule: Stringing the Chambers ~2 yrs./ 6 chambers ~1/2 time for stringing backup is top-down and bottoms-up estimate of time per wire December 2, 2009 CLAS12 Detector Review

Safety and Quality Assurance Issue Mitigation heavy equipment engineering review; procedures; training; clasweb.jlab.org/wiki/index.php/Safety cleanliness Class-10,000 clean-room, cleaning procedures, protective clothing high-voltage power current-limited to 40 mA low-voltage power voltage limited to 7.5 V use of magnets, motors follow EH&S manual on elec. safety electrical connections continuity and isolation checks wire placement accuracy parts inspections, surveys; tight controls on wire tension and end-plate deflection wire breakage “stress-tests”, temp., g-force limits pre-installation operability full commissioning plans (on wiki) installation accuracy micro-switches, post-installation surveys December 2, 2009 CLAS12 Detector Review

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 December 2, 2009 CLAS12 Detector Review

CLAS Drift Chambers : History Operating successfully for ~10 years …. A photo of the first “Reg. 3” chamber moving into Hall B December 2, 2009 CLAS12 Detector Review

Problems in the CLAS Drift Chambers We’ve had a couple of problems: ~60 severe* / year 16 broken wires 5 - 10 adb per yr. better now? ~ 10 lv per yr. worse now? * severe problems/ breakthroughs in elog December 2, 2009 CLAS12 Detector Review

CLAS Drift Chambers : History …. with good resolution mid-cell resolution is 200 - 250 mm cell average: 310, 315, 380 mm; for R1, R2, R3 …. at the same voltage, with same efficiency a Ar/CO2 shows no conventional aging NIM A449 (2000) 81 December 2, 2009 CLAS12 Detector Review

Conclusions Large project: 18 chambers, 90K total wires Reliable design: will achieve resolution and efficiency goals Low risk cost and schedule: based on detailed knowledge from CLAS High probability of success: experienced people December 2, 2009 CLAS12 Detector Review