glast lat projectdoe/nasa review of the glast/lat project, aug. 14, 2001 robert p. johnson 1 glast...

GLAST LAT Project DOE/NASA Review of the GLAST/LAT Project, Aug. 14, 2001

Robert P. Johnson 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Silicon-Strip Tracker/Converter

Robert P. JohnsonU.C. Santa CruzTracker Subsystem Manager

[email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope


Robert P. Johnson 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


Robert P. Johnson 3

Recommendations from FebruaryRecommendations 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.


Robert P. Johnson 4

LAT Tracker Peer Design ReviewLAT 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.


Robert P. Johnson 5

Silicon-Strip DetectorsSilicon-Strip Detectors

• Hamamatsu Photonics (HPK) detector prototypes satisfied all of our requirements.

• A preproduction run is in progress at HPK, with >300 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.

0

50

100

150

200

250

50561 50563 50565 50567 50569 50571 50573

HPK 1rst + 2nd LotAverage Run Leakage current

50562

50563

50564

50565

50566

50567

50568

50570

50571

50572

Run #

Run #

< i > = 186 nA

Cur

rent

(nA

)

Average leakage current per run for 10 preproduction HPK SSD runs.


Robert P. Johnson 6

Mechanical DesignMechanical 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.


Robert P. Johnson 7

Tray Panel ConstructionTray Panel Construction

Structural Closeout WallMCM Closeout Wall

Inside

Outside

Inside

Outside

Graphite fixture for closeout and tray panel assembly.

Tray panel: 4 C-C closeout sides, Al core, C-fiber face sheets.


Robert P. Johnson 8

Tracker Mechanical/Thermal InterfaceTracker 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).


Robert P. Johnson 9

Tower-Level Mechanical ModelTower-Level Mechanical Model

Typical 1st Mode Shape of the Flexure Mounted

Tower Support

Mode Description of Mode Shape Bottom Tray Fixed Support

(Hz)

Flexure Mount Support

(Hz)

1,2 Cantilever bending mode from compliant support 363 125,1303 Tower module vertical accordion mode - 2944 Tower module torsional mode - 375

5,6 Tower module cantilever bending mode - Lateral - 424,4357-10 SuperGLAST tray drumhead mode 444 to 448 447 to 48511 Top tray drumhead mode 527 534

12-20 Standard tray drumhead mode 542 to 554 553 to 555

1st Mode Flexure Deformation


Robert P. Johnson 10

Tray Assembly: LaddersTray Assembly: Ladders

• Assembly of prototype ladders, including encapsulation, has been completed at two Italian vendors (MIPOT and G&A)

• Measured alignment of completed ladders meets our specifications.

MIPOT alignment errors distribution

0

12

3

45

6

7

89

10

-20 -15 -10 -5 0 5 10 15 20

mm

Encapsulated Wire Bonds

Ladder edge-bonding fixture



Tray Assembly: Ladder MountingTray 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.

Mounting the first ladder onto a tray panel.

4 ladders mounted

SSDs Bias Circuits

Tungsten

Panel

MCM



Electronics Design: Readout ASICElectronics Design: Readout ASIC• Migrate design from HP 0.8 mm to HP 0.5 mm 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 testall features are functional.

64 amplifier-discriminator channels. Redesigned w.r.t. BTEM version. AC coupled to discriminator.

4-deep event memory (addressed by TEM)Custom layout

2 custom DACs I/O Cells

Control logic, command decodersStandard-cell auto route

Cap

Calibration mask and capacitors

I/O pads and protection structures

Trigger and Data mask registersStandard-cell auto route



Electronics Design: Controller ASICElectronics 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 ms (TBR) limit on the TOT.

Full prototypes are under test for both the TSMC (0.25 mm) and HP (0.5 mm) CMOS processes.

Layout of the GTRC chip in the TSMC process.



Electronics Design: PWBsElectronics 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.



Tracker MCM AssemblyTracker MCM Assembly

Wire bonds from a readout ASIC to flex

Bonding a pitch adapter to an MCM PWB.

• 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.



Tracker Electronics Test SystemsTracker Electronics Test Systems

• Systems for complete testing of the prototype ASICs are in progress.• Conceptual designs are complete for

• ASIC wafer probingprobe cards and PWBs are being designed.• MCM production testingcustom VME module is in hand.• MCM burn-inPWB design is in progress.

• Work is in progress to define the detailed test vectors and procedures for tray and tower electronics testing.

Test system for ASIC wafer probing.



Tracker Test PlansTracker 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



Tracker PDR PreparationsTracker 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.

glast lat projectdoe/nasa review of the glast/lat project, aug. 14, 2001 robert p. johnson 1 glast...

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