WBS:1.4.2.2.1: Tracking for CLAS12 Agenda, Aug 31 meeting: forward DC prototyping rate effects in central detector and forward SVT SVT technology and development Meetings every two weeks - Wednesday - 10 pm Progress in all 3 areas; at this meeting I’ll concentrate on: The physics at 12 GeV is typified by higher momentum tracks and the reactions of interest have smaller cross-sections, so the main requirements for the tracking system is good momentum resolution, e.g. 1% at 5 GeV/c is good for our missing-mass resolution, and also the ability to operate at a higher luminsosity fo 10^35. The detector solution is a Silicon vertex tracker and the forward drift chambers. We have highlighted this sub-system because it is vital to the physics program and is relatively expensive to build.

Forward Drift Chambers Measure charged tracks (5o – 40o) Forward drift chambers Design: same concept as present chambers: NIM A449(2000)81 6 sectors, 3 regions 2 super-layers/region 6 layers/super-layer 112 wires/layer (24000) on-board pre-amps Here again is a picture of the CLAS12 detector with the fwd. dc’s highlighted. They are designed using the same concepts as the present chambers which have been operating successfully since the winter of 97/98 and are described in a NIM article. In each sector of CLAS12 we plan to have three chambers (we call them “regions”); each region has two superlayers of six-layers each; each layer has 112 sense wires for a total of about 24000 instrumented sense wires. Pre-amps are mounted on the chamber on specially-built printed circuit boards (PCB). CLAS12

Forward Tracker hexagonal cells 6-layer superlayers

Forward Drift Chamber: new features Better momentum and angle resolution more constant velocity, good mechanical tolerance Higher rate capability smaller cell solid angle, shorter time window closer wire spacing (~ 70%) thicker wire (20 mm a30 mm) faster gas (88:12 Ar:C02 a92:08 Ar:CO2) Need prototypes ! goals features To reiterate: to get good resolution we need an approx. constant drift velocity (easier to calibrate) and good mechanical tolerance on the chambers themselves and to operate at high luminosity we need many, small drift cells. These new features, smaller cells, thicker wire, faster gas, need prototyping.

Forward Tracker: R&D and Design New features that require prototypes smaller cells, thicker wire, less CO2 higher voltages, denser-spacing on pcb’s multi-cell prototype: study hv plateau, signal cross-talk, noise levels, movement of wires Features that require most design work Chamber “boxes” - esp. attachments, relative alignments, ease of installation and surveying On-chamber custom circuit boards Our most important prototype is the multi-cell prototype. It will specifically look for possible negative consequences of going to smaller cells with thicker wire and using a faster gas: e.g. the possibility that the chamber could be “noisy”, that the wires might move from higher electrostatic forces, and that the higher voltages might cause excessive current draw on pcb’s. To emphasize: our design is a SMALL extrapolation from our current design, but we reduce the technical risk to insignificant levels by prototyping. On the issue of design work, we need to design in from the start the alignment and installation procedures. Although technologically straignt-forward, our on-chamber circuit boards are a custom design and will take a fair amount of design labor.

Forward DC Prototype facsimile of Region 1 area (highest wire density) subtend both superlayers (36 wires wide X 12 high) 12 X 12 wires actually strung 144 sense wires, ~350 field wires ~ 500 wires, 1000 feed-throughs eight perimenter posts -> realistic endplate ‘sag’ 1.5 m X 0.35 m endplates four circuit boards two ‘HVTB’, two ‘STB’

Forward DC Protoype: parts endplates: two (1.5 X 0.35 m.), 500 holes eight post assemblies gas bag: foils and sealing assemblies four circuit boards: 15 X 15 cm each, 72 thru-holes STB: 72 SIP’s each (144 total), 6 regulators, layers? HVTB: 1000 feed-through assemblies: plastic, trumpet, crimp pin 250 m. Gold-plated Tungsten wire 750 m. Gold-plated Aluminum wire

Forward DC Protoype: procurement costs Item Description Estimate Scaled Cost endplates 500 holes 1.5 X 0.35 m. 15 k$ CLAS: 50$/total wire a 17 K$ X 3 (small order) a 50 k$ wires, pins, feedthroughs 250 m. - tungsten 750 m. - aluminum 1000 feedthroughs 20 k$ posts, gas bag attachments, other parts 10 k$ circuit boards 2 STB’s 2 HVTB’s 2 k$ X 5 (small order) a 10 k$ Total 60 k$

Forward DC Protoype: procurement costs Item Description Labor needs endplates 500 holes 1.5 X 0.35 m. specifications, vendor selection, quality control wires, pins, feedthroughs 250 m. - tungsten 750 m. - aluminum 1000 feedthroughs specifications, vendor selection, quality control posts, gas bag attachments, other parts design, procurement, construction circuit boards 2 STB’s 2 HVTB’s design, specifications, vendor selection, quality control Total ~ ½ FTE mech., ~1/2 FTE elec.