DC12: Tracking/simulation needs CLAS12 Drift Chambers Physics specifications high efficiency at large solid angle (5 o to 40 o ; 50% f coverage at 5 o ) good resolution (~1% dp/p; ~ 1mrad angle) Basic design six 6-layer superlayers; 112 wires per layer minimum dead area March review momres, FASTMC, gsim12 basic design works May 8, 2008CLAS12 Detector Review - backups DC12: further sim./recon. needs No further sim/recon work needed for basic design Additional work IS needed for: detailed design of Moller shielding detailed design of forward vertex tracker design and specifications for chamber alignment and magnet field measuring systems May 8, 2008CLAS12 Detector Review - backups Software: how to improve tracking use double hits (CLAS-Note ) use segment angle as well as location in link table enforce consistency between l-r ambig. resolution and global track parameter early find tracks with no TOF hit write special utility to find out-of-time accidental tracks; use unusual pattern of time residuals to measure time derive off-diagonal terms in error matrix May 8, 2008CLAS12 Detector Review - backups Performance: Drift Chamber Rate Capability Rate Capability: times CLAS factor of 3: one cells angular size 1/3 as large o instead of 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 May 8, 2008CLAS12 Detector Review - backups 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 dont require track reconstruction estimates of track efficiency and fakes input random background with correct average occupancy use a cut-based track finder generate tracks with background; reconstruct tracks the gold standard May 8, 2008CLAS12 Detector Review - backups Rate Simulations : methods Fractional occupancy efficiency is ok if less than 4% of the wires are hit estimated with GEANT3 and GEANT4, t = 150 ns GEANT3 tested against data taken with a solenoidal shield/absorber DC-NIM study May 8, 2008CLAS12 Detector Review - backups Forward Tracker: Momentum Resolution fractional momentum resolution vs. momentum different configurations May 8, 2008CLAS12 Detector Review - backups Material in Tracking System MaterialThickness (cm)Rad. Length (%) air20 cm0.07 % Silicon (6-layers)0.18 cm1.9 % CO cm0.8 % mirror2 cm0.8 % DC (gas + wires)25 cm0.35 % air95 cm0.3 % DC (gas + wires)40 cm0.5 % air80 cm0.25 % DC (gas + wires)50 cm0.6 % May 8, 2008CLAS12 Detector Review - backups Endplates fit into Frames New idea: frames are multi-part and pre-bowed frame endplate May 8, 2008CLAS12 Detector Review - backups Region 2 conceptual design May 8, 2008CLAS12 Detector Review - backups Feedthroughs Electrical standoff: surface (G10 and plastice): ~ 0.25 cm / 1000 V gas: keep surface E-field below 20 kV/cm (50?) smooth electrode: 3000 V 0.15 cm gap Material of tip: plastic (increases field at wire - no dead area, hot? metal (decreases field at wire - no hot areas, dead? May 8, 2008CLAS12 Detector Review - backups CLAS12 DC Fixtures/Accessories Assembly fixtures (build the boxes) to place endplates into pre-bowed frames Stringing fixtures (string the chambers) pre-tension at correct orientation string, tension, test Mounting fixtures (position accurately) cryostat-chamber connection move chamber to accurate docking mechanism allow easy access for repair, maintenance Chamber disconnect junction box May 8, 2008CLAS12 Detector Review - backups Material Choices Endplates aluminum: easy to machine, longer feedthroughs, large eddy-currents, stronger than G10 G10-CR: vice-versa Frames stainless steel: non-magnetic enough? Feedthroughs Noryl (with glass beads) metal tips: machined or formed? wire: Aluminum, Cu-Be, stainless? electrical stand-off constructability May 8, 2008CLAS12 Detector Review - backups Electrical issues: calculations for a 2 cm. (s - f) wire spacing diam. (microns)voltagefields (kV/cm) sfgsfgsfggain e e e e0 4 May 8, 2008CLAS12 Detector Review - backups Prototypes: Reg. 1 prototype: test: estatic stability, excessive current draw, construction techniques status: ~200/800 wires done, ready for first tests wire-test chamber: (baby chamber) test cathode emission from (thin) field wires measure surface fields near endplates status: next week, bring laser to ODU ISU beam test: test efficiency, gain versus position along wire one test done, second due soon May 8, 2008CLAS12 Detector Review - backups CLAS12 DC Work Plans Build R1 prototype box Clean endplates, re-assemble String, operate R1 prototype Verify design Build wire-test chamber Chamber tests: field wire diameter Specifications for wire Preliminary electronics design Conceptual design for Reg. 2 Conceptual design for Reg. 3 Decide whether to use assy. fixture Build torus-chamber prototype Study cable routing Decide on angle between endplates Drawing, specs for assy. fixture Develop detailed stringing procedures Drawing, specs for stringing fixtures ISU beam test Decide on feedthrough design Drawing, specs for feedthroughs Drawing, specs for R1 boxes Drawing, specs for R2 boxes Drawing, specs for R3 boxes Conceptual design: mounting, installation Drawing, specs for chamber-torus attachments Design complete Oct 08 NOW 2008 May 8, 2008CLAS12 Detector Review - backups DC12 Status (winter 07-08) Decide on endplate, feedthrough, wire material guidance from small prototype chambers mainly electrical stand-off and noise issues Decide on frame designs guidance from Reg. 2 prototype constructability and accuracy of pre-bowed endplates Large prototype tests improve procedures, look for unknown problems Proceed with drawings, vendor qualification, May 8, 2008CLAS12 Detector Review - backups Operational Problems & Solutions Broken wires larger diameter sense wires stress-free mounting system more extensive shake-down better temperature control of hall (already implemented) Circuit board corrosion go to conformally-coated pcbs better humidity control (already implemented) finer segmentation (partially implemented) High current draw stricter irradiation procedures (already implemented) better humidity control (partially implemented) more HV channels (planned for near-term) May 8, 2008CLAS12 Detector Review - backups Risks: Stringing the Chambers Harder to do Region 1: 7.5 mm cell; 1.8 m long wire ratio L/D ~ 235 (was 175) lower wire tension ? Easier to do smaller chambers 7 m endplate 4 m endplate chambers are flat stereo wires are all parallel sense wire: 20 m 30 m less breakage, easier to see ! same design for all regions May 8, 2008CLAS12 Detector Review - backups Cost Comparison: Other Drift Chambers Phenix DCs (jet-cell type with 36 super- modules) Mechanical costs: $250/sense wire (but 7-8 other wires per sense wire) $50/total wire CLEO-c DCs (open-cell with square cells) Mechanical costs: $40/total wire (labor not included) CLAS12 DCs (open-cell with hexagonal cells) Mechanical costs: $180/sense wire $49/total wire (labor included) May 8, 2008CLAS12 Detector Review - backups CLAS12 / CLAS costs (not labor) ratio task CLAS12 DCs have 70% as many wires Some tasks dont depend on wire count May 8, 2008CLAS12 Detector Review - backups CLAS12 Drift Chambers : Labor task man-weeks PED tasks May 8, 2008CLAS12 Detector Review - backups Methods of Cost Estimation Endplates: cost = (a + b * nwires) * inflation; a =.2, b =.8 boxes: cost = old cost * 0.75 * inflation Wires, pins, feedthroughs; cost = old_cost * wire_ratio * inflation May 8, 2008CLAS12 Detector Review - backups Costs: Stringing the Chambers Estimate the time; use labor cost tables Bottoms-up estimate - based on previous experience 2 people, 15 mins. per wire for stringing stringing per se takes 1/3 to 1/2 of the time 3 crews of 5 stringers for ~ 2 years techs / scientists doing support, QA/QC Top-down - simple scaling of total elapsed time, accounting for fewer wires May 8, 2008CLAS12 Detector Review - backups CLAS12 Drift Chamber Procurements/Expenses Task k$ stringing labor - estimate time - use labor rate May 8, 2008CLAS12 Detector Review - backups CLAS12 Drift Chamber: Construction Costs PED: 0.34 M$ Const: 4.50 M$ Total: 4.84 M$ May 8, 2008CLAS12 Detector Review - backups CLAS12 Drift Chambers: Cost Same concept as present CLAS chambers Small extrapolations from current designs smaller cells, thicker wire, faster gas Cost estimates based on prior experience 180$ / sense wire : mechanical costs major cost is wire-stringing re-use most electronics Schedule and manpower allocation: prior experience Experts on staff and in CLAS collaboration May 8, 2008CLAS12 Detector Review - backups 6 construction categories: Boxes- frames, endplates Wire - sense, field, guard Wire Attachments - feedthroughs, pins Electronics Boards - high voltage, signal Assembly Fixtures - to string chambers Installation Fixtures - to install chambers 6 construction phases: Design - accomplish physics goals, fit Award - detailed specs, vendor selection Accept - receive, inspect Assemble - build complete chambers Install - install chambers Commission - see particles CLAS12 Drift Chamber Construction: Scenario Analysis 36 scenario node points where problems might arise May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design changes to other detector elements force revisions: group coordination award vendors cannot meet specs, cost: extensive budgetary estimates, many vendors accept part out of spec.: pre-planned, rapid inspection procedures assemble unforeseen problems in fit: fully tested with prototypes install unforeseen problems in installation: installation models built, tested commission finished chamber: detailed plans already developed Boxes - scenario analysis May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design specs too tight or too loose: extensive previous experience award vendors cannot meet specs, cost: extensive budgetary estimates, many vendors accept part out of spec: test wire spool-by-spool as it arrives, pre-planned procedures assemble unforeseen problems with chamber stringing: extensive experience, much time allocated install - not applicable - commission chambers noisy or inefficient: extensive previous experience Wire - scenario analysis May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design specifications set wrong: extensive previous experience award vendors cannot meet specs, cost: extensive budgetary estimates, many vendors accept part out of spec: test part-by-part as it arrives, pre- planned procedures assemble unforeseen problems with feedthrough installation: previous experience, much time allocated install - not applicable - commission - not applicable - Wire Attachments - scenario analysis May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design changes to wire pattern force revisions: group coordination award vendors cannot meet specs, cost: extensive budgetary estimates, many vendors accept part out of spec: test part-by-part as it arrives, pre- planned procedures assemble unforeseen problems with board installation: previous experience, much time allocated install - not applicable - commission noisy operation: prototyping Electronics boards - scenario analysis May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design changes to other detector elements force revisions: group coordination award vendors cannot meet specs, cost: standard items, many vendors accept part out of spec.: pre-planned, rapid inspection procedures assemble separate parts dont fit: much time allocated install - not applicable - commission - not applicable - Assembly fixtures - scenario analysis May 8, 2008CLAS12 Detector Review - backups phasepossible problems and mitigation design changes to other detector elements force revisions: group coordination award vendors cannot meet specs, cost: fairly standard parts, many vendors accept part out of spec.: pre-planned, rapid inspection procedures assemble - not applicable - install unforeseen problems in installation: installation models built, tested commission - not applicable - Installation fixtures - scenario analysis May 8, 2008CLAS12 Detector Review - backups Drift Chambers for CLAS12 Response to Mar Reviewers Comments We strongly support the Hall B groups plan to build full-scale prototype drift chambers as soon as possible--- chamber is partially strung, many tests performed --- to test new metal trumpets as well as integrated plastic feed-throughs--- prototype tests done, go with metal-tipped We urge the group to --- explore cost-saving construction procedures --- endplate machining will likely be less expensive (probably due to more computer-controlled milling machines); in new budget --- urge the group to explore design modifications to the region 2 chambers that will maximize active area near the CLAS12 beamline we are investigating an endplate in a trussed frame design which gives more solid angle at small ; slightly less at larger --- to do detailed Monte Carlo simulations --- should include estimates of the material in the silicon detectors done May 8, 2008CLAS12 Detector Review - backups response to comments (continued) --- include systematic variations of component and installation alignments important; will do ---how best to combine tracking information from the silicon strip detectors and the drift chambers strip-dc matching is fully efficient; --- studies of chamber misalignment --- we agree that alignment is important; chamber design includes alignment considerations; we also plan a detailed magnetic field map --- installing helium bags TOF folks dont like it; were studying it May 8, 2008CLAS12 Detector Review - backups