The D Silicon Microstrip Tracker SMT

1
The DØ Silicon Microstrip Tracker (SMT)

• Design
• Production Assembly
• Readout
• Installation Commissioning
• First Results

• Breese Quinn, FNAL
• Vertex2001
• September 24, 2001
• (presented by Frank Lehner, Universitaet Zuerich)

2
SMT Design
12 F Disks
4 H Disks
6 Barrels

• 4-layer barrel cross-section

SMT Statistics
3
SMT Design
4
SMT Design

• Require good 3D track reconstruction performance
  for high-pT (top, Higgs, EW, NP) and low-pT (B)
  tracks out to ? lt 3
• Momentum resolution less than 10 at pT 1 GeV/c
• Impact parameter resolution within 30 ?m
• Forward H disks are employed to achieve these
  resolutions at high ?

5
Production Assembly Devices

• Ladders
• 3-chip 72 single-sided, axial ladders in the two
  outer barrels
• 6-chip 144 double-sided, axial/90 ladders in
  the four inner barrels
• 9-chip 216 double-sided, axial/2 ladders in all
  barrels
• Ladders have a mechanical accuracy of 2-5 ?m
• Wedges
• F Disks 144 double-sided, 15, 68 chip wedges
• H Disks 962 back-to-back single-sided, 7.5, 6
  chip wedges
• Wedges have a mechanical accuracy of 5-10 ?m
• SVX IIe chip
• 128 channel 8-bit digital chip, with 32 cell
  pipeline depth
• 1.2 ?m rad-hard technology
• 106 MHz digitization, 53 MHz readout
• Rise time set to integrate 99 of charge in 100
  ns
• Over 2.3 million wirebonds were made to chips

9-chip ladder
H wedge
SVX IIe chip
6
Production Assembly Testing

• Probe Test
• Debug bad strips (broken capacitors), bonds,
  chips, etc.
• Determine the V-I characteristics of the sensors
• Measure V-max p-side breakdown voltage
  (micro-discharge effect)
• Burn-in
• Bias the ladder or wedge and test the readout for
  72 hours
• Measure pedestals, noise, gain and check sparse
  readout
• Laser
• Expose biased detectors to a narrow laser scan
• Measure the depletion voltage and leakage
  currents and identify dead channels
• Readout tested again after the detector is
  mounted on a barrel or disk

V-max
Fail
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Production Assembly Failure Modes

• Sensor lithography defects
• A silicon manufacturing problem produced p-stop
  isolation defects in the 90 stereo ladders.
  This resulted in a 30 yield from the
  manufacturer.
• Microdischarge effect
• With negative p-side bias on double-sided
  detectors, we observed microdischarges producing
  large leakage currents and noise at a breakdown
  voltage.
• The effect occurs along the edges of the p
  implants, where large field distortions and
  charge accumulations result from misalignment of
  electrodes with implants.
• Effect moves to n-side after type inversion.

8
Production Assembly Detector Quality

• Detector classification
• Dead channel lt 40 ADC count response to laser
• Noisy channel gt 6 ADC count pedestal width
• Grade A less than 2.6 dead/noisy channels
• Grade B less than 5.2 dead/noisy channels
• Only used mechanically OK Grade A and B detectors

6-Chip Ladders
Channel Fractions ()
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Production Assembly Alignment

• Internal alignment was
• accomplished using a CMM
• machine that aligns ladders
• and wedges to lt 20 ?m.
• e.g. Rotation ? along long axis
• of ladder (? 10 ?m ? 3 ?m
• error on impact parameter)

Barrel 1 Rotations
? (mm)
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SMT Readout Data Flow
HV / LV
I,V,T Monitoring
8 Low Mass Cable
19-30 High Mass Cable (3M/80
conductor)
25 High Mass Cable (3M/50 conductor)
3/6/8/9 Chip HDI
KSU Interface Board
CLKs
CLKs
Adapter Card
SEQ
SEQ
SEQ
Sensor
SEQ Controller
Optical Link 1Gb/s
Detector volume
Platform
Serial Command Link
VRB
VRB
VRB
VBD
68k/PwrPC
1 5 5 3
VRB Controller
Bit3
VME
PC
L3
MPM
Counting House
SDAQ
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SMT Readout Electronics

• Interface Boards
• 8 crates (144 boards) located inside the detector
  volume
• Refresh signals and adjust timing
• SVX monitoring and power management
• Bias voltage distribution

• SEQuencers
• 6 crates (120 boards) located on the detector
  hall platform
• Use SVX control lines to effect data acquisition,
  digitization and readout
• Convert SVX data to optical signals

• VRBs (VME Readout Buffers)
• 12 crates (120 boards) located in the counting
  house
• Data buffer pending L2 trigger decision
• Input _at_ 5-10 kHz L1 accept rate 50 Mb/s/channel
• Output _at_ 1 kHz L2 accept rate 50 Mb/s

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Installation
Fiber Tracker

• Cylinder installation was completed on 12/20/00
• A ½ cylinder of 3 barrels and 6 F disks was
  inserted into each end of the CFT bore
• H Disk installation was completed on 2/6/01
• The cabling (15,000 connections) and electronics
  installation was completed in May 2001

Calorimeter
Low Mass Cables
SMT
High Mass Cables
Interface Boards
13
Commissioning

• The entire detector has been connected and
  powered
• 15 of the devices are not in the readout
  because the SVX chips cannot be downloaded.
• 10 ladders, 18 F wedges, 20 H wedges
• Problems could be with cables, connectors, chips,
  etc. We will debug each of them during the
  October/November shutdown, and expect to recover
  more than half.
• Currently collecting calibration and alignment
  data

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Comissioning

• Online event display for SMT commissioning

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Charge Collection

• A cluster is defined as a contiguous sequence of
  strips with
• Each strip ? 6 ADC counts
• Cluster ? 12 ADC counts
• Timing setting a-b-c represents a signal delay of
  (a-1)?132 ns (b-1)?18 ns (c-1)?2 ns
• Preamp bandwith (pabw) sets the integration time
• With 396 ns bunch spacing, all charge should be
  collected with any of the pabw settings
• Higher pabw results in lower noise level

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Timing and S/N

• Higher preamp bandwith does not significantly
  reduce noise on n-side

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Alignment Residuals

• SMT-only tracking with at least 4 hits
• Magnet off data
• Similarity of residuals from reconstruction with
  ideal and survey geometries indicates excellent
  internal alignment of the SMT

Ideal Geometry
Survey Geometry
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Alignment SMT CFT Track Matching

• Tracks were found separately in the SMT and the
  Central Fiber Tracker (CFT)
• SMT tracks were extrapolated to the CFT at which
  point the track offsets were measured
• Magnet off data

?r? -3 ? 36 ?m
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J/???? Candidate Sample
PRELIMINARY
Sherry Towers
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Conclusions

• Design/Production
• Experience with double-sided detectors has led to
  the decision to use single-sided silicon for the
  upgrade.
• Should work toward simpler designs in the future.
  For example, using 6 different sensor types
  resulted in extensive logistical complications.
• Assembly/Installation
• Alignment results show that the DØ SMT was
  assembled and installed extremely well.
  Congratulations to the SiDet and DAB staff!
• Commissioning
• The SMT was the first major DØ Upgrade detector
  system fully operational for Run 2A. More than
  85 of the channels were available for readout on
  startup, and most of the remaining channels will
  be debugged and recovered by November.
• Results
• Very nice calibration (and first look at
  physics!) results have been produced from the
  early data, as we continue to better understand
  our detector.

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Alignment Beam
Distance of Closest Approach vs. ?
Vertex Position