Feb. 2, 2007 CLAS12 Upgrade Workshop Mac Mestayer

Feb. 2, 2007 CLAS12 Upgrade Workshop Mac Mestayer
Tracking for CLAS12 Purpose: introduce the concepts and design decisions identify any flaws in design identify risks get ready for March review of drift chambers Structure: packets containing focus questions and issues I will give a general introduction to issues 2-minute silent periods for jotting down ideas followed by open discussions (next slide) “Believe nothing, no matter where you read it, or who said it, unless it agrees with your own reason and your own common sense.” -Siddhartha Gautama Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Scope of Talk physics a specifications a design concepts design specifics (SVT, followed by DC) layout (wires, layers, superlayers, etc.) electronics, cabling, utilities summary of decisions (with pros/cons) prototype tests, future simulations simulated performance (effcy. vs. rate, resolutions) budget and schedule discussion SVT, DC discussion discussion discussion discussion Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Tracking: physics a design
Physics constraints: electron beam higher momentum tracks, smaller cross-sections Detector goals: good momentum and angular resolution capability to run at L=1035cm-2s-1, good vertex resolution, robust Detector design: central solenoid and Moller absorber; forward torus forward tracker: Si strips + standard R1, R2, R3 central tracker: Si strips Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Physics constraints: electron beam electron angle important exclusive reactions missing mass technique wide kinematic coverage Event types: small cross-sections multi-particle final states large background rates Goals: Specifications: measure Gv 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 layer occupancy < 4% good acceptance Df ~ 50% at 5o check !! Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Discussion: physics a spec’s a design
are the tracking spec’s adequate to do the physics? (need feedback from proposers) what studies could confirm this? specific studies with FASTMC; specifically, for an experiment with a charged track in the central region what are the options if the background rates are much higher than expected? what is the effect on the physics if the resolution went up by 1.5? if the minimum lab. angle were 6o? or some other moderate change to the spec’s? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

CLAS12 Tracker measure charged tracks (5o – 140o) Central tracker: single-sided Si strips barrel: 4 x 2, fwd: 3 x 2 DC’s: same concept as present chambers hexagonal cells 6 sectors, 3 regions 2 super-layers/region 6 layers/super-layer 112 wires/layer (24192) angled endplates on-board pre-amps not to scale ! Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

SVT: spec’s a design concepts
Specifications: Central Design Features L = 1035/cm2/s -solenoidal shield -separated fwd.-bck. - large backgrounds many strips small stereo angle (fewer ambiguities) four 2-layer superlayers good dp/p, dq 5 T central field 75 mm readout pitch dp/p ~ 1/(rin - rout)2 +/- 1.5o stereo angles good acceptance butt-joint design wire-bonded staves reliability identical sensor cards Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

SVT Design Decisions single-sided strips mature technology; more material 75 mm strip pitch read out: 150 mm 4x2 (SVT); 3x2 (FSVT) robust track-finding only two sensor types rectangular (SVT) trapezoidal (FSVT) 1.5o (stereo): SVT good enough; dq ~ df 9o (stereo): FSVT fits 20-gon; too many ambig.’s ? butt-joint construction simple; easy to simulate wire-bonded staves need good mechanical support SVX4 chips well-known Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Discussion: SVT design
dbl-layer technology has less mult. scatt. - why not use it? isn’t 6 layers in fwd. direction overkill? - how many are needed? is the clocking of the central polygon optimal to minimize dead areas? why have we chosen SVX4? what is its time window and charge sensitivity? is wire-bonding too risky? place for MicroMegas? what about FSVT? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Drift Chambers : spec’s a design concepts
Specifications: Fwd.Design Features: L = 1035/cm2/s -solenoidal shield -separated fwd.-bck. - large backgrounds occupancy = solid angle x time window x thickness small cells, 30 mm wires six 6-layer superlayers good dp/p, dq, df planar chambers identical cells (easy to calibrate) ~linear drift velocity +/- 6o stereo angle good acceptance flanged endplates Df ~ 50% of 2p at 5o reliability self-supporting design Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Drift Chamber Design Decisions
solenoidal shield necessary for 1035 fwd./bck. separation fwd. trks.; magnet interactions high ∫B∙dl torus good dp/p for fwd. tracks 6x6 layers robust track-finding +/- 6o stereo better f resolution; more ambigs. planar; self-supporting identical cells, easy to calibrate, survey, repair 112 wires/layer cell-size; cost 30 mm sense wire 92/08 Ar:CO2 faster, linear xvst, strong, more reliable stringing on-chamber amplifiers long cable runs re-use hv, lv, ADB, TDC lots of spares; cost Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Discussion: Drift Chamber design
is 6o the optimal stereo angle? f resln. vs. ambig.’s how to support region 2? why 30 mm wire diameter? on-board amps? discriminators? what technology? re-using hv, lv, ADB’s, FASTBUS, cables: crazy? what is hv, lv segmentation? expected chamber lifetime? what kind of feedthroughs are you using? is 112 wires/layer too few? too many? gas choice? endplate material choices? trade-offs due to self-supporting design robustness and serviceability issues Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

R&D Plans: Drift Chambers
New features that require prototypes smaller cells, thicker wire, less CO2 higher voltages denser-spacing on pcb’s cross-talk, hv stand-off higher electro-static forces less quenching multi-cell prototype: study hv plateau, signal cross-talk, noise levels, movement of wires all-plastic feedthroughs; where is wire sensitive? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Design Plans: Drift Chambers
Features that require most design work Chamber “boxes” - esp. attachments, relative alignments, ease of installation and removal On-chamber PCB’s Chamber environment - temperature and humidity control Cable routing - mundane but important HV, LV segmentation - turn off bad areas Region 2 attachment Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

R&D Plans: SVT Features that require prototypes: wire-bonding several sensors assembly frame read-out pitch adapter Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Design Plans: SVT Features that require most design work Assembly structure: rigid, little material Cable routing - mundane but important Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Conceptual Design: MicroMegas
study performance of a radial drift in a 5T field is MM suitable for the forward vertex tracker? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Discussion: Protoyping Plans
Prototypes required: any others required? SVT: several segments wire-bonded mechanical assembly prototype MicroMegas: cylindrical mesh conical mesh for forward part Drift Chambers full-sized Reg. 1 feedthrough/wire sensitivity prototype Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

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 don’t 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 Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Performance: Drift Chamber Rate Capability
Rate Capability: times “CLAS” 3: cell angular size one-third as large 5 - 40o, 80% as many wires : smaller time window thicker wire, higher field, faster gas : less x-ray absorption smaller cells 1.5: better shielding larger solenoid, better absorber need to optimize #cells/layer; study specialized shielding Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

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 ! Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Estimates of occupancies
Background study: Vlassov et al.: estimates occupancies ~0.1% in SVT1 and Reg1,sl1 GSIM12 and RECSIS12 now running GEANT4 program now running soon! Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Central tracking: 10 hits/layer
Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Study of rate effects in a 6-layer Silicon tracker with a TOF layer effect of 40 X background a fake tracks +/- 3o stereo +/ 1.5o stereo normal background Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Track Momentum Resolution
present CLAS: approx. 350 microns (DC_NIM) times 1.7 (CLAS_NIM) (dp/p)2 = (0.003*p)2 + (0.002) {at 35o} CLAS12 goal: dp/p < 1% at 5 GeV/c 250 micron accuracy/layer (100 microns/s.l.) measure B-field, alignment procedures Simulation: = (0.0004*p)2 + (0.008) {at 35o} using MOMRES Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Torus magnetic field Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Forward Tracker: Resolution
dp/p, dq, df, dx - plotted versus p 1% 0.5 mrad at 35o 0.5 mrad 100 microns Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Central SVT Resolution
4% at 1 GeV/c 10 mrad at 1 GeV/c < 1mm vertex resolution Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

some physics results using FASTMC Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Smearing of Qgp in e D a e p n

Discussion: Simulation of Performance
is the background really that low? what kinds of simulations are necessary to estimate track resolutions? are present simulations adequate? are special simulations necessary to study DC- FSVT track matching? is CLAS12 tracking adequate to achieve the CLAS12 physics goals? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Forward Drift Chamber Work List

Forward Drift Chamber Budget
Procurement, expenses: M$ Labor: M$ Total: 4.83 M$ Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Simulation Work Needed - now!
re-do MOMRES and/or hand calculations for recent configurations estimate tracking resolution from material thickness, point resolutions a FASTMC use FASTMC to estimate mass resolutions and other “physics” quantities choose reactions involving SVT, FSVT and DC’s; study effects of changing resolutions study rate-dependence of efficiency use GSIM12 and RECSIS12 to study tracking efficiency as a function of realistic event background better estimate of forward f resolution use GSIM12 and RESCIS12 estimate occupancy in various layers of the SVT, FSVT and DC’s use GEANT3, GEANT4 or DINREG choose optimum stereo angles requires track-finding and selection compare Silicon vs. MicroMegas requires FSVT-DC matching as well as MOMRES studies of central tracking Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Project Overview & Responsibilities
Design & Build SVT: Los Alamos, UNH, Moscow State, JLab Region 1: ODU Region 2: JLab? Region 3: Idaho State MicroMegas: Saclay Miscellaneous prototyping SVT and/or FSVT assembly frames plastic vs. metal-tipped feedthroughs alternative multiplexing boards Software c++ - based tracking software Other Magnet Mapper Cost Estimates Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Discussion: Work Plans
what would it take to put YOU behind the wheel of a brand-new CLAS12 tracking project? are there projects not listed which you would be interested in doing? do you have concerns about project scope or time-table? other concerns? what’s your prediction for the Super Bowl score? Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Forward Tracker Procurements/Expenses

CLAS12 / CLAS costs (not labor)

Forward Tracker: Labor
man-weeks Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Forward Tracking Improvements
better momentum, angle resolution more constant velocity, good mechanical tolerance higher luminosity operation smaller cell solid angle, shorter time window good vertex resolution Si strip detector more robust thicker sense wire finer lv, hv segmentation easier to remove, fix good engineering ! Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Tracking Improvements
smaller “boxes” easier to align, install less expensive endplates larger diameter sense wire stronger higher E field, more constant drift velocity shorter sensitive time fewer wires better HV, LV segmentation faster gas (e.g. 92:8 AR:CO2) Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Operational Problems & Solutions
Broken wires more extensive “shake-down” better temperature control of hall (already implemented) Circuit board corrosion go to copper, fiber-glass pcb’s better humidity control (partially implemented) finer segmentation (partially implemented) High current draw stricter irradiation procedures (already implemented) more HV channels (planned for near-term) Feb. 2, CLAS12 Upgrade Workshop Mac Mestayer

Feb. 2, 2007 CLAS12 Upgrade Workshop Mac Mestayer

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