CLAS12 Tracking Design (ca. 2005) a basic design parameters Central tracker: single-sided Si strips 150 mm pitch barrel: 4 x 2, +/- 2o stereo fwd: 3 x 2, +/- 12o stereo SVT DC’s: same concept as present chambers hexagonal cells 6 sectors, 3 regions 2 super-layers/region +/- 6o stereo regions at ~ 2, 3, 4 m. 112 wires/layer (24192) 250 mm resolution reg. 1 reg. 2 reg. 3 March 23, 2009 Hall B meeting

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, 112 wires/lyr. six 6-layer superlayers 30 mm wires good acceptance Df ~ 50% of 2p at 5o pre-bowed frames low wire tensions self-supporting design March 23, 2009 Hall B meeting

Forward Tracker: Expected Resolution dp/p, dq, df, dx - plotted versus p - at 35o 1% 0.5 mrad These results were calculated with MOMRES; in good agreement with sim/rec results from GEANT3/RECSIS12 and GEANT4/trak. Backup slide shows what happens with/wo a vtx. tracker and at 350 micron accuracy. 0.5 mrad 100 microns March 23, 2009 Hall B meeting

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 March 23, 2009 Hall B meeting

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. March 23, 2009 Hall B meeting

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! March 23, 2009 Hall B meeting

Endplates: many precise holes Number of Holes 4925 feedthrough holes 12 survey 3 datum & alignment 28 bolt & attachment 0.200 mm true position a “50 mm” 1.7 m March 23, 2009 Hall B meeting

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 March 23, 2009 Hall B meeting

CLAS12 Stringing Fixture Backup is recent photo March 23, 2009 Hall B meeting

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 March 23, 2009 Hall B meeting

Steps in Stringing March 23, 2009 Hall B meeting

Installing Pre-tensioning Wires - before we start stringing - use springs on guard wires - gradual release of tension March 23, 2009 Hall B meeting

Stringing the Chamber March 23, 2009 Hall B meeting

Installing Pre-amplifier Boards On-board pre-amplifier boards and high-voltage distribution boards are installed after wires are strung. March 23, 2009 Hall B meeting

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 March 23, 2009 Hall B meeting

Model of Torus and Chambers very useful: installation cabling access March 23, 2009 Hall B meeting

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 !! March 23, 2009 Hall B meeting

Installation and mounting scheme Linkage system allows quick and accurate installation Positioning accuracy reproducible to 25 mm March 23, 2009 Hall B meeting

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 March 23, 2009 Hall B meeting

Total cost: 4.6 M$ March 23, 2009 Hall B meeting Forward Tracker Outside Costs Labor (man-weeks) Total (k$)   Techs. Engrs. Designers Scientists Pd. Univ. Total Labor Sub-tasks MT ET ME EE MD ED VU S U. Cont. U. Staff man-wks k$ Design chamber 21 10 36 1 110 135 Buy endplates, frames 368 11 4 7 3 6 28 59 114 482 Buy wires, pins, feedthroughs 655 13 16 52 90 745 Buy cleanroom supplies 80 5 9 20 91 171 Box assembly 19 8 32 82 151 Design stringing fixture 2 26 44 Build clean room, stringer 141 17 53 86 226 String, instrument chamber 1550 102 60 150 328 560 2,110 Design stb/hvtb 15 45 Lay out, buy stb/hvtb 321 40 116 437 Total $3,115 202 35 25 65 85 66 146 264 924 $1,522 $4,637 PED 30 12 216 $314 CONSTRUCTION 172 24 34 263 708 $1,208 $4,323 PED: labor Const: procurements $1,565 Const: expenses $1,550 Const: labor PED: total Const: Total CLAS12 Total March 23, 2009 Hall B meeting

Lots of work ! March 23, 2009 Hall B meeting

Lot to buy ! March 23, 2009 Hall B meeting

Plans for next year: Buy reg. 2 endplates, frames Build reg. 2 boxes hire lead dc technician in July work in Jlab’s, ODU’s cleanrooms Buy wire, feedthroughs, misc. Build strong-backs, installation fixtures String first Reg. 2 chamber hire first stringing crew in fall March 23, 2009 Hall B meeting