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The Construction Status of the ATLAS Silicon Microstrip Tracker D. Ferr


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Title: The Construction Status of the ATLAS Silicon Microstrip Tracker D. Ferr

The Construction Status of the ATLAS Silicon
Microstrip Tracker D. Ferrère on behalf of the
SCT collaborationDPNC, University of Geneva
  • General Description
  • Silicon Detectors
  • Electronics
  • Electrical Tests
  • Module Assembly
  • Summary Status

Atlas at LHC
LHC will provide protons and ions collisions
A designed luminosity of 1034 cm-2s-1 p-p
collision with 14 TeV in the center of mass
The Atlas Detector
Physics Motivations
  • Requires a good tracking performance
  • Secondary vertices
  • Impact parameters resolution
  • Track isolation
  • Measurement of high momentum particles
  • Higgs in SM and in MSSM
  • Supersymmetric Particles
  • B physics (CP violation, ...)
  • Exotic physics

Simulated Event in the Inner Detector
SCT Environment
  • 23 overlapping interactions every bunch crossing
    (at the full Luminosity)
  • A bunch-bunch crossing every 25ns (40MHz)
  • Maximum equivalent 1 MeV neutron fluence after 10
    years is 2.1014 n/cm2
  • Operating temperature on silicon detectors is
    -7oC to contain the reverse annealing and the
    leakage current
  • Maintenance will likely require yearly warm-up of
    2 days at 20oC and 2 weeks at 17oC
  • Material lt 0.4 X0 at the outer SCT envelope
  • Operation in a 2 Tesla solenoid field

SCT in the Inner Detector
  • SCT
  • 4 Barrels 2x9 wheels
  • 4 different module types in the wheels
  • h lt 2.5

The SCT Semiconductor Tracker
Barrel diameters B3 568 mm B4 710 mm B5 854
mm B6 996 mm
4088 Modules 61 m2 of silicon 15,392
silicon wafers 6.3 million of readout channels
5.6 m
1.04 m
9 wheels
1.53 m
4 barrels
9 wheels
The SCT module types
2112 Barrel modules 936 Outer Forward
Modules 640 Middle Forward Modules (incl. 80
Short Middle) 400 Inner Forward Modules
Module Pictures
  • A Barrel Module
  • 2 daisy chained detectors / side
  • The Kapton hybrid is bridged
  • over the detectors
  • The cooling pipe is on the connector
  • side
  • An Outer Forward Module
  • 2 daisy chained detectors / side
  • The Kapton hybrid is at the far end
  • The cooling area is common with
  • the mounting blocks

Silicon Detector Pictures
1 Barrel detector type 5 Forward detector
types W12 Inner Module W21 W22 Middle
Module W31 W32 Outer Module
Single sided p-in-n detectors
768 strips
Size 6x6 cm2
285 mm thick
  • Barrel Pitch 80 mm
  • Forward Pitch
  • W31 and W32 161.5 mrad
  • W12, W21 W22 207 mrad

Scratch pads for identification Corresponds to
DB serial number
Silicon Detector Status
The detectors passed the Production Readiness
Review in August 2000. The production delivery
started this year.
The detector purchases is distributed as followed
Manufacturers Hamamatsu (Japan) CiS (Germany) Sintef (Norway)
Contribution 79 17 4
Sensor types All Wedges Barrels
On going qualification
Delivery status of Hamamatsu detectors in Geneva
Silicon Detector Some Specifications
  • Total leakage current at 20 oC lt6 mA_at_150V and
    lt20 mA_at_350V
  • Leakage current stability to increase by not
    more than 2 mA _at_150V in dry air over 24 hours
  • Depletion Voltage lt 150V
  • R bias 1.25 /- 0.75 MW (Poly-silicon or
    implanted technology)
  • C coupling gt 20 pF/cm _at_ 1kHz
  • C interstrip lt 1.1pF/cm _at_ 100kHz _at_ 150V bias
  • R interstrip gt2x R bias at operating voltage
  • Strip metal resistance lt15 W/cm
  • Strip quality a mean of gt99 good readout strips
    per delivery batch. Not less that 98 /detector

  • Total leakage current lt250 mA up to 450V _at_ -18 oC
  • Leakage Current stabilityto vary by no more than
    3 in 24 hours at 350V at -10 oC
  • Strip defects Number of strip defects
    (dielectric metal) within pre-irradiation
    acceptance level
  • Charge collection Maximum operating voltage for
    gt90 of maximum achievable charge 350V

Silicon Detector Quality Control
Quality Control consists of systematic checks for
Visual Inspection and IV scan sub-sample tests
(10 of the detectors) Depletion voltage, full
strip test, metal strip resistance and Interstrip
Up to now only few rejections has been made based
on visual defects and extra currents.
Example of W31 normalized current _at_ 20oC
Silicon Detector Quality Control
0.082 of detective strips out of 172 detectors
The defective strips are identified by Hamamatsu
and the QC at the Institutes. The full strip test
allows to identify all possible defects
like Open, Short, bias resistor break, pin hole,
oxide punch through, implant break. The
detectors are slightly biased during the
measurement and up to 100V DC is put on the
strips. LCR meter allows to measure coupling
capacitance and the relative bias resistor.
0.044 of detective strips out of 170 detectors
Hamamatsu series production delivered in Geneva
Silicon Detector Irradiation
The detectors are irradiated using 24 GeV protons
at CERN PS. All strips are grounded and the
backplane is biased to 100V during the
irradiation. Typical annealing is done at the
minimum of the beneficial and reverse annealing.
Silicon Detector Charge Collection after
The detectors were annealed 7 days at 25oC after
an irradiation of 3x1014 p/cm2 The readout was
made with SCT 128A chips (DMILL technology). A
Ru106 source was used for the injected
charge. The Signal to noise ratio is for a strip
length of 6 cm The measurement was taken at 18oC
D. Robinson
A S/N plateau around 171 is reached above 350V
for all the Hamamatsu detectors
Similar results are obtained for the other
detector purchases
The Front End Electronics
Binary ABCD chips are based on DMILL BiCMOS
  • Noise with detectors (12 cm strips) lt 1500 e-
  • Efficiency 99
  • Occupancy due to Noise 5x10-4
  • Double pulse resolution 50ns for 3.5fC following
    3.5 fC signal
  • Shaping time 20 ns
  • Pipeline Length 3.2 ms (128 locations)
  • Functionality temperature range -15 to 30oC
  • Power dissipation lt 3.8 mW/channel
  • Specified total radiation dose 2x1014 n/cm2
  • 10 Mrad

The Front End Electronics
ABCD 3T Trimming function
The readout chips passed the PRR in July
2001. Pre-series have started with 35 wafers
already delivered. In November 200 wafers are
expected. The measured yield on the pre-series is
spread from 10 to 50 and the expected yield in
average is 26. ATMEL think they can improve it!
  • Yield consideration based on
  • All analog and digital functionalities are OK
    (tested with threshold, bias and frequency scan)
  • No Icc or Idd problem
  • No bad channels

The wafer screening for the Quality Control will
be done at 3 places CERN, RAL and SCIPP.
Current testing time 9 hours/wafer Will be
decrease during prod by a factor 2
The Module Test Set-up
The SCT DAQ (software and hardware) readout test
set-up is the same in all the laboratories.
  • Tests on modules
  • Measured gain curve (with internal calibration
  • Hit occupancy versus comparator threshold
    without signal (Noise Occupancy)
  • Determination of ENC (from response curve and
    Noise Occupancy)
  • Pulse shape through variation of calibration
    pulse delay
  • Power consumption at different settings
  • Various digital function checks (pipeline data

Signal and ENC determination
  • S-curves
  • Measure hit occupancy as a function of the
  • Fit error function to occupancy S-curve
  • Determines mean signal rms

Module Performances
  • Pre-irradition
  • ENC noise 1400-1500e-
  • NO _at_1fC 1-2 x 10-5
  • Post-irradition
  • ENC noise 1900e-
  • NO _at_1fC 2-3 x 10-4

Acceptance criteria 5x10-4
KEK Test Beam Median Charge
Preliminary results from N. Unno
A small difference between barrel and end-cap
modules is observed and could be due to Larger
effective pitch for the forward and less charge
Barrel and End-cap modules are functioning well
and are very similar
KEK Test Beam Efficiency and Noise Occupancy
Preliminary results from N. Unno
Test Beam Results Spatial Resolution
Spatial resolution in strip coodinate (/- 20mrad
stereo angle) ? 23mm ? compatible with digital
resolution for 80mm pitch
  • Gives spatial resolution in X/Y
  • s(X) 20mm
  • s(Y) 750mm

Multiple Modules in the System Test
  • Determine performance of individual modules
  • Measure noise and inter-module effects
  • Optimize grounding and shielding in realistic

Noise Performance in the System Test
Tests on multi-modules barrel setup
Noise Comparison System Test versus Single Module
ENC System Test ENC Individual Module ENC
Noise Occupancy
Module Assembly
Barrel alignment system
Aligned forward detector pairs onto transfer
Parallel module production will take
place Barrel KEK, RAL, LBL, Oslo Starting at
the end of this year Forward Freiburg, Geneva,
Melbourne, Nikhef, MPI, UK-North, Valencia
Module Mechanical Tolerances
SCT Philosophy Build modules to a sufficiently
high tolerance that alignment corrections within
the module are not needed for track
Physics requirement Alignment accuracy rms (in
Direction (cyl. Coord.) Barrel Forward
R 100 50
f 12 12
z 50 200
Internal module build tolerances Alignment
tolerance (in micron)
Barrel Forward
XY wafer to wafer plane in 1 plane 4 4
XY back to front plane 8 8
XY relative to mounting holes 30 20
Z surface of silicon detectors 40 100
Forward disc sector Middle cooling circuits,
cooling blocks and low mass tapes
Barrel sector close-up view of brackets, pipes,
Barrel support structure is under construction
Forward support structure is ready for FDR
Summary and Status
  • Detectors
  • The series production started beginning of 2001
    and is well on the way
  • 36 of the detectors are delivered and the
    quality is very good
  • Chips
  • ABCD3T passed production readiness review and
    first lot of production wafers
  • are expected soon
  • Modules
  • Barrel modules passed FDR and will start
    production at the end of the year
  • Forward modules require 1 more round of hybrid
    production before going to FDR
  • Engineering, Off-detector Components, power
  • A series of FDRs started in spring
  • First parts are/will be soon order for production

Appendix - Typical Power Consumption
Module current and power
Before Irradiation After Irradiation
Idd (mA) 550 750
Vdd (V) 4.0 4
Icc (mA) 950 560
Vcc (V) 3.5 3.5
Power (W) 5.2 5
  • ICC ? after irradiation due to the optimization
    of the FE setting
  • before irr Ipre 220 mA and Ishap 30 mA
  • after irr Ipre 150 mA and Ishap 24 mA

Appendix Prototype Components of the Forward
Kapton Hybrid
Appendix Optical Links
Opto-packages on the dog-leg (Barrel)
Forward Opto-plug-in PIN receiver (Clock
Control BPM) 2 VCSEL lasers for data links
Appendix Forward Electrical Performances
From G.Moorhead
Appendix Forward Electrical Performances
From G.Moorhead
Appendix Thermal Simulation
  • Requirement Prevent Thermal Runaway
  • Facts of life
  • Leakage current (4 detectors of the module)
    after 10 years in the LHC reaches
  • 2mA _at_ 500V _at_ -10 C (spec lt1. 0mA _at_450V _at_-
    18 C)
  • Increased ASIC power estimates now 6.8W per
  • ASICs are close to detector and module designs
    are optimized to limit heat
  • transfer to detectors.
  • Some thermal design features
  • Baseboard or spine are made of TPG (Thermo
    Pyrolitic Graphite).
  • Conductivity 1700 W/ m/ K along length
  • Improved hybrid substrate (metallised CF or CC)
    reduces hybrid ASIC
  • temperatures, reducing convection ( 0.5W
    with CF)
  • Evaporative C3F8 cooling - extensive system
    prototyping has been done.
  • It looks promising using -20 C at the
    cooling block

Appendix Thermal Simulation
Module Power Consumption
After annealing (10 days continuous warm
_at_ 40MHz
  • observed on some modules increase of Idd current
    (up to x2 normal current) but still within specs
    for current and total module power (6.8W/module)
  • on effected module current comes from all chips
  • under investigation ...