Charged Particle Tracking for CLAS12
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Transcript of Charged Particle Tracking for CLAS12
CLAS12 Detector Review
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 DesignBVT (mixed Si/MM?)FVT (stereo angle?)
Design optionsSimulation resultsTechnology reviews
December 2, 2009 Mac Mestayer
Maximizing efficiency and resolution at high ratesKey decision points
Basic overview
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 Mac Mestayer
CLAS12 Detector Review
Goals: Specifications:measure flux-factor accurately
q ~ 1 mraddp/p < 1%
select an exclusive reaction; e.g. only one missing pion
dp < .05 GeV/cdq p < .02 GeV/c sinq df p < .02 GeV/c
small cross-sections
L = 1035/cm2/shigh efficiency
good acceptance Df ~ 50% at 5o
Physics goals a general design spec’s
December 2, 2009 Mac Mestayer
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 1035 cm-2 s-1
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
CLAS12 tracking: ca. 2008
DC’s
torus
solenoid
May 8, 2008 Mac Mestayer
reg. 1reg. 2
reg. 3
Si tracker
CLAS12 Detector Review
Silicon trackers and drift chambers
May 8, 2008 Mac Mestayer
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
CLAS12 Detector Review
BST & FVT AssemblySilicon 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 Mac Mestayer
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 Mac Mestayer
Résultats3 dispositifs ont été étudiés:- 4x2 SI ( = 1.5°, et = 43 mm)- 4x2 MM ( = 0 et 90°)- 2x2 SI+ 3x2 MM
pT/pT SI(+MM)
q MM
Résultats - 2
SI(+MM) z MM
CLAS12 Detector Review
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 Mac Mestayer
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.
CLAS12 Detector Review
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 segmentationDecember 2, 2009 Mac Mestayer
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 Mac Mestayer
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 Mac Mestayer
Present forward tracker (DC, FST)
• 3x2 layers• trapezoidal tiles• 12° stereo angle• acceptance: 5°35°
• 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
FST
Strip layout:
Simulation & Reconstruction 10/30/2008 S.Procureur
CLAS12 Detector Review
Torus magnetic field
•∫B∙dl ~ 3 T-m
•highest field for forward tracks
December 2, 2009 Mac Mestayer
B (t
esla
)
Scattering angle (degrees)
CLAS12 Detector Review
Match DC track to FST hit
December 2, 2009 Mac Mestayer
98% of DC tracksextrapolate within+/- 1 cm.
So, how many background hits in the ‘circle of confusion’?
Resolutions with DC+FST(electrons at q = 15°, now from GEMC!):
FST greatly improves the vertex resolution, , q and p
5 times better20 times better
Simulation & Reconstruction 10/30/2008 S.Procureur
DC+FST – resolution with protons
Much better vertex resolution with FST (and resolution at high p)
(protons at q = 15°):
3-4 times better8-10 times better
CLAS12 Detector Review
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 Mac Mestayer
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 Mac Mestayer
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 rateDecember 2, 2009 Mac Mestayer
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 Mac Mestayer
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 Mac Mestayer
CLAS12 Detector Review
Backup slides on DC12
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
measure cross-section accurately
q ~ 1 mraddp/p < 1%
planar chambersidentical cells (easy to calibrate)250 mm accuracy/layer
select an exclusive reaction; e.g. only one missing pion
dp < .05 GeV/cdq p < .02 GeV/c sinq df p < .02 GeV/c
~linear drift velocity+/- 6o stereo angle
small cross-sections
L = 1035/cm2/shigh efficiency
small cellssix 6-layer superlayers30 mm wires
good acceptance Df ~ 50% of 2p at 5o pre-bowed frameslow wire tensionsself-supporting design
Physics goal Physics spec. Design feature
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Superlayer Wire LayoutStaggered “Brick-Wall” Hexagonal
colored circles
representdrift
distances
fieldfieldsensefieldfieldsense....
.sensefieldfieldsensefieldfield
6 sense layers, 2 guard layers, 14 field layers: 1 superlayerDecember 2, 2009 Mac Mestayer
CLAS12 Detector Review
Rationale for Design Decisions
6x6 layers robust track-finding+/- 6o stereo better f resolution than CLASplanar; self-supporting identical cells, easy to
calibrate, survey, repair112 wires/layer enough for 1035 operation30 mm sense wire 92/08 Ar:CO2
faster, linear distance-vs-time, strong, more reliable stringing
low wire tension thinner endplateson-chamber amplifiers good signal/noisere-use HV, LV, ADB, TDC
lots of spares; cost savings; better segmentation
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
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 ! use 30 mm wire!
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Number of Holes4925 feedthrough holes12 survey 3 datum & alignment28 bolt & attachment
1.7 m
Endplates: many precise holes
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Endplate Details
0.200 mmtrue positiona “50 mm”
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Endplates fit into Frames
Receive endplates- inspect- measure hole positions- cleanReceive frames- inspect and clean- pre-bow endplate and frames- bolt and glue into frames
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Box Assembled-endplates attached-attachment brackets affixedNext ---- mount on stringing fixture- insert feedthroughs- install survey points- string wires- attach circuit boards- QA/QC
Chamber Ready to String
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
CLAS12 Stringing Fixture
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Parts: wire a circuit board
conductive rubber
circuit board
crimp pin
feedthrough
endplate
signal routing:wires a pre-amp
wire
December 2, 2009 Mac Mestayer
circuit board
CLAS12 Detector Review
Stringing wires between “slanted” endplates
endplates
“gravity” stringingwires: 9 cm - 4 m longwires strung individuallywires attached by crimpingwires positioned by “trumpet”
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Steps in Stringing
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Installing Pre-tensioning Wires
Pre-tensioning- before we start stringing- use springs on guard wires- gradual release of tension
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Stringing the Chamber
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Installing Pre-amplifier Boards
December 2, 2009 Mac Mestayer
On-board pre-amplifier boards and high-voltage distribution boards are installed after wires are strung.
CLAS12 Detector Review
1 mA2 - 3 electrons
Pre-amp2 mV/mA
Post-ampx 10 - x 3030 mV disc.
drift chamber
75 ft. cable
TDC’sLecroy 1877
new circuit boardsbased on old SIP’s
Electronics: Chamber a TDC
December 2, 2009 Mac Mestayer
re-use post-amps, TDC’s
CLAS12 Detector Review
Model of Torus and Chambers
December 2, 2009 Mac Mestayer
very useful:-installation-cabling-access
CLAS12 Detector Review
Tight-packing of Cables, Connectors
December 2, 2009 Mac Mestayer
CAD layoutsverified on a model:tight spacing dictated by requirement of50% f-coverage at 5o
multi-layer
composite
endplate !!
CLAS12 Detector Review
Installation and mounting scheme
December 2, 2009 Mac Mestayer
Linkage system allows quick and accurate installation
Positioning accuracyreproducible to 25 mm
CLAS12 Detector Review
Schedule: Stringing the Chambers
~2 yrs./ 6 chambers
~1/2 time for stringing
December 2, 2009 Mac Mestayer
CLAS12 Detector Review
Safety and Quality Assurance
December 2, 2009 Mac Mestayer
Issue Mitigationheavy 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 mAlow-voltage power voltage limited to 7.5 Vuse of magnets, motors follow EH&S manual on elec. safetyelectrical connections continuity and isolation checkswire placement accuracy
parts inspections, surveys; tight controls on wire tension and end-plate deflection
wire breakage “stress-tests”, temp., g-force limitspre-installation operability
full commissioning plans (on wiki)
installation accuracy micro-switches, post-installation surveys
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 Mac Mestayer
CLAS12 Detector Review
CLAS Drift Chambers : History
• Operating successfully for ~10 years ….
December 2, 2009 Mac Mestayer
A photo of the first“Reg. 3” chambermoving into Hall B
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 Mac Mestayer
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 efficiencya Ar/CO2 shows no conventional
aging
December 2, 2009 Mac Mestayer
NIM A449 (2000) 81
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 Mac Mestayer