GLAST Proposal Review

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GLAST Large Area Telescope Silicon-Strip
Tracker/Converter Robert P. Johnson U.C. Santa
Cruz Tracker Subsystem Manager johnson_at_scipp.ucsc
.edu
2
Silicon-Strip Tracker/Converter

• Outline
• Recommendations from the February review
• Tracker Peer Design Review
• Tracker Technical Progress
• Silicon-Strip Detectors
• Mechanical Design
• Tray Assembly
• Electronics Design
• Electronics Assembly
• Tracker Test Plans
• Tracker LAT PDR Preparations

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Recommendations from February

• Build an explicit Tracker reserve of at least 4
  months into the fabrication schedule.
• This has been done.
• Produce detailed test plans, including testing of
  the electronics beyond the expected operational
  conditions.
• Mechanical and electrical test plans have been
  drafted.
• Detailed procedures for prototype ASIC testing
  have been drafted, and those tests are just
  beginning.
• Work is in progress on building the electronics
  test systems.
• Detailed test procedures and verification matrix
  for testing during production remain to be
  written.
• Add milestones to the Tracker development
  schedule
• Detailed schedules have been put together (in MS
  Project) for completion of the prototype trays
  and the Tracker engineering model during the
  coming year.

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LAT Tracker Peer Design Review

• Draft Preliminary Design Report LAT-TD-00156.
• 21 additional Tracker documents prepared for the
  PDR
• Requirements
• Mechanical/thermal design report
• Electronics conceptual design and specifications
• Mechanical and electrical interface
  specifications
• Grounding and shielding plan
• Reliability analysis
• Parts lists
• Mechanical and electrical test plans
• The review was held June 19, 2001, with a panel
  that included 2 outside experts one with SSD
  experience in HEP one aerospace expert.
• The outcome of the review was generally positive.
  All questions were answered. Work is in
  progress on complying with the detailed
  recommendations, in preparation for the PDR.

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Silicon-Strip Detectors

• Hamamatsu Photonics (HPK) detector prototypes
  satisfied all of our requirements.
• A preproduction run is in progress at HPK, with
  gt300 SSDs manufactured and tested.
• The preproduction SSDs are of excellent quality.
• SLAC has tendered a contract for the first
  production run at HPK.
• 2 European firms are still working on prototype
  runs, but HPK production can meet our full
  demand.

Current (nA)
Average leakage current per run for 10
preproduction HPK SSD runs.
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Mechanical Design

• Detailed design of the tray panels (thin
  converter, thick converter, top bottom) is
  complete.
• Prototype tray panels are being fabricated both
  in Italy and the U.S.
• Two tower-module assembly methods have been
  devised and will be tested in September
• Stacked trays.
• External fixture.
• A full prototype tower will be constructed from
  prototype trays and mass-model trays for
  vibration testing before construction of the
  Tracker engineering model.

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Tray Panel Construction
Tray panel 4 C-C closeout sides, Al core,
C-fiber face sheets.
Graphite fixture for closeout and tray panel
assembly.
Structural Closeout Wall
MCM Closeout Wall
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Tracker Mechanical/Thermal Interface

• A conceptual design was completed for attachment
  of the Tracker to the Grid
• Blade flexures to avoid stress from CTE
  differences.
• Thermal gasket to aid the transfer of heat into
  the Grid.
• Some modeling has been completed (next slide).
• Some details need more work (such as how to
  ensure adequate compression of the gasket).

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Tower-Level Mechanical Model
Typical 1st Mode Shape of the Flexure Mounted
Tower Support
1st Mode Flexure Deformation
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Tray Assembly Ladders

• Assembly of prototype ladders, including
  encapsulation, has been completed at two Italian
  vendors (MIPOT and GA)
• Measured alignment of completed ladders meets our
  specifications.

Ladder edge-bonding fixture
Encapsulated Wire Bonds
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Tray Assembly Ladder Mounting

• Fixtures for precision mounting of ladders onto
  tray panels have been designed and tested in
  Italy.
• The same vendors as for ladder assembly will do
  this work during production.

Bias Circuits
SSDs
Panel
Tungsten
MCM
Mounting the first ladder onto a tray panel.
4 ladders mounted
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Electronics Design Readout ASIC

• Migrate design from HP 0.8 ?m to HP 0.5 ?m CMOS
  process.
• Substantial redesign of analog front end (now 2.5
  V).
• LVDS on all I/O (except hard reset and config.
  reg. output).
• Configuration register now is SEU hardened
  (tested with heavy ions).
• Config. reg. divided into 5 pieces now
  nondestructive read.
• System clock and output-register clock are on
  continuously.
• Old FIFO for event buffering is now RAM.
• Full prototype is under test?all features are
  functional.

Control logic, command decoders Standard-cell
auto route
4-deep event memory (addressed by TEM) Custom
layout
Trigger and Data mask registers Standard-cell
auto route
2 custom DACs
I/O Cells
Cap
64 amplifier-discriminator channels. Redesigned
w.r.t. BTEM version. AC coupled to discriminator.
Calibration mask and capacitors
I/O pads and protection structures
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Electronics Design Controller ASIC

• All digital, standard cell design, except for
  LVDS I/O cells.
• SEU hardened configuration register.
• Ground-up new design in VHDL synthesis, auto
  place and route.
• Functionality is similar to the BTEM chip, but
  many interface and data format details are
  changed.
• 25 ?s (TBR) limit on the TOT.

Full prototypes are under test for both the TSMC
(0.25 ?m) and HP (0.5 ?m) CMOS processes.
Layout of the GTRC chip in the TSMC process.
14
Electronics Design PWBs

• Tracker MCM (readout module)
• PWB layout is complete.
• 7-chip mini version for initial system tests is
  in fabrication.
• Face-to-face meetings were held in L.A. last week
  with the vendor for the full-scale aramid-fiber
  version.
• Pitch adapter flex circuit. Prototypes are in
  hand from 2 vendors and are being used to study
  MCM assembly.
• Bias flex circuit prototypes are in fabrication.
• Flex readout cables
• Layout was completed on the first of eight.
• Quotations are in progress at 2 vendors.
• The final length still is undetermined.

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Tracker MCM Assembly

• Teledyne, in L.A., will solder SMT parts, bond
  the pitch adapter, mount ASICs, wire bond, test,
  and encapsulate.
• Face-to-face meetings were held with Teledyne
  last week in L.A.
• Work will begin immediately on tooling and on
  assembly of initial (non-functional) prototypes.

Bonding a pitch adapter to an MCM PWB.
Wire bonds from a readout ASIC to flex
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Tracker Electronics Test Systems
Test system for ASIC wafer probing.

• Systems for complete testing of the prototype
  ASICs are in progress.
• Conceptual designs are complete for
• ASIC wafer probing?probe cards and PWBs are being
  designed.
• MCM production testing?custom VME module is in
  hand.
• MCM burn-in?PWB design is in progress.
• Work is in progress to define the detailed test
  vectors and procedures for tray and tower
  electronics testing.

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Tracker Test Plans

• Environmental Testing
• LAT-TD-00154 Tracker Tray Test Plan
• LAT-TD-00155 Tracker Tower Test Plan
• Electronics Testing
• LAT-TD-00153 Test Systems for the Tracker
  Front-End Electronics
• LAT-TD-00191 Tracker Tower Electrical Test Plan
• LAT-TD-00246 Tracker Front-End Chip Test Plan
• LAT-TD-00247 Tracker Front-End Readout Chip Wafer
  Test Procedure
• LAT-TD-00248 Tracker Readout-Controller Chip
  Wafer Test Procedure
• LAT-TD-00249 Tracker TMCM Electrical Test
  Procedure

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Tracker PDR Preparations

• Update of the PDR documentation
• Improvement of the reliability analysis.
• Improved requirements documents.
• More complete electronics test plans, test
  procedures, and verification matrix.
• Completion of the prototype mechanical structure,
  including assembly tests.
• Vibration tests on trays. Possibly tower
  vibration, as well.
• Ion-beam SEL and SEU tests on Tracker ASICs.
• Test results on the Tracker ASICs in the full
  flight design, including an integrated test with
  both ASICs, a mini-MCM, and a full-length SSD
  ladder.
• Finalized baseline budget and schedule.