GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Silicon-Strip Tracker Converter
Robert P. Johnson
Santa Cruz Institute for Particle Physics
University of California at Santa Cruz
Tracker Subsystem Manager
johnson@scipp.ucsc.edu
R.P. Johnson, UCSC
1
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
LAT Tracker Subsystem
Outline
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LAT design overview
Tracker technical challenges
Derived Tracker requirements
Tracker technical description
• Mechanical design and prototyping
• Silicon-Strip detectors
• Electronics design and prototyping
Tracker organization and WBS
Tracker assembly
Tracker status
Tracker schedule and milestones
Tracker budget
Tracker issues
Conclusions
R.P. Johnson, UCSC
2
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
LAT Design Overview
Instrument
16 towers  modularity
height/width = 0.4  large field-of-view
Anticoincidence Detector Shield
Tracker
Si-strip detectors:
• 228 mm strip pitch
• 18 x,y measurement pairs
• 12 layers of 3% X0 converters
• 4 layers of 18% X0 converters
• 8.8  105 readout channels
Carbon-fiber composite structure
Calorimeter
R.P. Johnson, UCSC
3
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Technical Challenges
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Detector system: achieve nearly 100% efficiency for MIPs in the
detector active volume, with 60 micron spatial resolution.
– Silicon-strip detectors readily meet these requirements.
Electronics: operate nearly a million channels on <300 W while
maintaining sufficiently low noise for the Tracker to self trigger and
while handling a high readout rate with negligible dead time.
– Specialized ASICs have been under development for 5 years and
have demonstrated these capabilities in beam tests.
Mechanical structure: maintain high transparency to charged particles
while supporting detectors and electronics during launch.
– A mechanical structure based on honeycomb panels and carbonfiber composite materials is under development.
Modular design: minimize dead space within the tracking volume.
– Miniaturized electronics mounted on the edges of the panels.
Reliability: eliminate susceptibility to single-point failures.
– Two independent readout paths for every channel.
Assembly: large number of repetitive parts to assemble.
– Use industrial assembly techniques for electronics packaging.
R.P. Johnson, UCSC
4
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Derived Tracker Requirements
The following table is a summary of some of the requirements from the
Tracker Level-3 Requirements Document. These requirements derive
from the LAT Performance Specifications.
Conversion efficiency
Converter configuration
Geometric area
Aspect ratio
Single-plane detection
efficiency
Intrinsic angular resolution
Dead area
Self trigger
Dead time
Data noise occupancy
Mass
Power
R.P. Johnson, UCSC
>65% of gammas for E>10 GeV
Thin front (<3.5%) ; thick back (<25%)
>19,000 cm2
<0.45
>98% within the sensor fiducial area
<0.2 from two sensor planes
<12%
>90% efficient if 3 planes are crossed
<500 Hz noise rate
<10% at 10 kHz rate
<1 in 1000 channels per trigger
<586 kg, current estimate 487 kg
<259 W, current estimate 219 W
5
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Technical Description
Electronics
Module
• 16 layers of tungsten converter foils
19 Carbon-Fiber
Tray Panels
– 12 layers of 3% X0 converters
– Followed by four 18% layers
• x-y Si-strip detector pair closely
following each converter foil + 2
additional pairs at the bottom.
• Stiff composite “tray” panels support
SSDs on both faces with electronics
on two sides.
2 mm gap
CarbonFiber Wall
Readout
Cable
R.P. Johnson, UCSC
– Converters are on the bottom face, just
above the SSD plane
– 2-mm gap between trays
– Trays stack and align with pins in the
four corner posts
• Carbon-fiber sidewalls conduct heat
to the base and stiffen the tower.
• Electronics are based on 2 ASICs, PC
boards, and custom flex cables.
• 30.5 kg mass per tower
6
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tray Mechanical Design
•
Engineering and development by
Hytec, Inc., Los Alamos
– Machined carbon-carbon closeouts,
with metal inserts for fasteners
– Carbon-fiber face sheets, 4 or 6 ply
– Aluminum hexcel cores
– Parylene or metal passivation of
carbon surfaces
– Precision assembly fixtures
•
Early SBIR
prototype allcarbon tray
Flight-panel fabrication in Italian
Industry
Carbon-Fiber Face Sheet
Aluminum
Honeycomb Core
R.P. Johnson, UCSC
Closeout assembled from
four machined carboncarbon parts
f0 of completed assembly (with
SSDs and converters) > 500 Hz.
7
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Silicon-Strip Detectors
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Principal vendor, Hamamatsu Photonics, is already qualified, with
prototypes of the final design delivered and exceeding specifications.
Hamamatsu’s production capacity can satisfy all of GLAST’s needs.
Procurement is beginning NOW; ramping up to >500 sensors per month.
• AC-coupled, with polysilicon
bias resistors
• 8.95 cm square (6” wafers)
• 400 microns thick
• 384 strips
• 228 micron strip pitch
• 64 micron strip width
• Depletion < 150 V
• Leakage current <800 nA (avg.
<240 nA) per sensor
• Bad channel rate <0.2%
R.P. Johnson, UCSC
8
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Electronics
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•
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Low power (210 W for 884,736 channels); low noise (<105 occupancy).
Redundancy: 2 readout paths for every channel.
Low dead time: 20 MHz readout; event buffering at the front end.
Compact: readout module fits in a 4.2 mm gap along the tray edge.
Block diagram of the
data and control-signal
flow for the Tracker
readout system.
A full-scale, fullyfunctional prototype
system was built for
the BTEM.
R.P. Johnson, UCSC
9
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Electronics
The prototype electronics functioned well in the
beam test, but the design is being updated to
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reduce interference from clock transients
match the new tray size and SSD pitch
satisfy new T&DF requirements
follow all IPC and other relevant design rules
use space-qualified parts
facilitate assembly and integration
BTEM
Tracker
R.P. Johnson, UCSC
10
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Organization
GLAST Tracker
Subsystem Manager
R. Johnson UCSC
Tracker Scientist
Performance
H. Sadrozinski, UCSC
SSD Design,
Testing, Procurement
T. Ohsugi, Hiroshima U.
Mechanical, Thermal
System Engineer
T. Borden SLAC
Mechanical
Engineering Design
E. Swensen, Hytec Inc.
System Engineering
Quality Assurance
Resources, Reporting
Italian Tracker Project
Manager
R. Bellazzini, INFN-Pisa
INFN Tracker
Development Engineer
A. Brez, INFN-Pisa
Tracker Electronics
Lead Engineer
D. Nelson, SLAC
Tracker Power Supplies
& Housekeeping
D. Nelson, SLAC
Electrical Interconnects
D. Nelson, SLAC
Electronics Mechanical
Assembly & Integration
G. Paliaga, UCSC
I & T Supervision
O. Millican, SLAC
R.P. Johnson, UCSC
Ladder, Tray, Tower
Production Supervisor
A. Brez, INFN-Pisa
Electronics System
Testing
W. Kroeger, UCSC
Front-End ASIC Design
E. Spencer, UCSC
Readout Controller
ASIC Design
J. Olson, SLAC
11
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker WBS Organization
GLAST LAT IPO
Stanford
LAT Tracker Subsystem
WBS 4.1.4
Italy, Japan, SLAC, UCSC
Tracker Management
WBS 4.1.4.1
Subsystem Mgr: R. Johnson, UCSC
Italian Mgr: R. Bellazzini, Pisa
Syst. Eng.: T. Borden, D. Nelson, SLAC
Tray Subassembly
WBS 4.1.4.3
SSD Procurement
T. Ohsugi, Hiroshima
Japan, Italy, SLAC
Tray Mechanical
T. Borden, SLAC
SLAC, Italy, Hytec
Readout Electronics
D. Nelson, SLAC
UCSC, SLAC
Tray Assembly
A. Brez, INFN-Pisa
Italy
R.P. Johnson, UCSC
Tower Structure
WBS 4.1.4.4
Tower Engineering
T. Borden, SLAC
SLAC, Hytec
Cable Plant
G. Paliaga, UCSC
UCSC
Tower Assembly
A. Brez, INFN-Pisa
O. Millican, SLAC
Italy, SLAC
Test & Calibration
WBS 4.1.4.5
Reliability and QA
WBS 4.1.4.2
T. Borden, SLAC
Instrument I&T Support
WBS 4.1.4.7
SLAC
Mission I&T Support
WBS 4.1.4.8
SLAC
Mission Ops
WBS 4.1.4.9
Engineering Model
SLAC
Qualification Towers
SLAC
Flight Towers
Italy
12
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
TKR Flight-Tower Design & Assembly
Tower Structure (walls, fasteners)
Engineering: SLAC, Hytec
Procurement: SLAC
SSD Procurement, Testing
Japan, Italy, SLAC
SSD Ladder
Assembly
Italy
10,368
Tower Assembly
and Test
SLAC (2)
Italy (16)
2592
Tray Assembly
and Test
Italy
342
18
342
Cable Plant
UCSC
Electronics Design,
Fabrication & Test
UCSC, SLAC
648
R.P. Johnson, UCSC
Composite Panel & Converters
Engineering:
SLAC, Hytec, and Italy
Procurement: Italy
13
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Assembly
•
Detector ladders (2592 + spares):
– SSD production monitoring: Hiroshima
– Edge bond SSDs, wire bond, test, encapsulate wires: 2 Italian lines
•
Electronics multi-chip readout modules (648 + spares):
– Standard chip-on-board industrial technology (quote from Teledyne)
– Test/burn-in equipment and procedures supplied by UCSC
•
Carbon-composite panels (342 + spares):
– Fabricate in Italian industry
– Includes converter foils and SSD bias circuits
•
Tray assembly in 2 Italian lines (342 + spares):
– Precision mounting of 4 ladders on each face
– Attach electronics boards
– Wire bond the electronics to the detectors, test, and encapsulate
•
Tower assembly (2 at SLAC and 16 in Italy):
– Stack 19 trays
– Attach readout cables and sidewalls
– Testing with the calibration system and with cosmic muons
R.P. Johnson, UCSC
14
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Status
• Mechanical:
– Design is complete for the tray
panels and assembly fixtures, with
assembly of prototypes in progress.
– Mechanical/thermal testing of the
detector attachment scheme and of
the sidewalls is in progress.
– A flexure concept and other
interface issues for Tracker
attachment to the grid is under
study.
• Detectors:
– The CDR of the SSD design,
specifications, and prototype
performance was held Jan. 30, ‘01.
– A preproduction run of 400
detectors is underway at HPK.
– A schedule for production of all
flight units is being finalized with
Hamamatsu Photonics.
R.P. Johnson, UCSC
• Electronics:
– Mask layout for the design update of
the 2 ASICs is in progress and close
to completion.
– Prototypes of the modified amplifierdiscriminator design are under test.
– Layout of the new PC board and flex
circuits is underway.
– External interfaces are well defined.
• Ladder and Tray Assembly:
– A new ladder-assembly fixture is
under test in Pisa.
– Designs exist for all tray assembly
fixtures.
– Mockup trays are under fab for testing
detector/converter attachment.
• Documentation:
– Level-3 specs are under review.
– Level-4 specs and ICDs are in
progress.
– Work is in progress on a database for
fabrication and assembly work.
15
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Documentation
Item
Management
Memorandum of Agreement – Italy
Implementation Plan
Specifications
TKR Level-3 Requirements
TKR Electronics Level-4 Requirements
Readout ASIC Specifications
Controller ASIC Specifications
SSD Specifications
TKR Mechanical/Thermal Lvl-4 Requirements
Interface Control Documents
TKR – T&DF ICD
TKR – GRID ICD
TKR electronics-mechanical
Plans and Procedures
Assembly Procedures
Ladder Assembly
Multichip Module Assembly
Tray Assembly
TKR Tower Assembly
SSD Production Monitoring
Electronics Test Plan
Tower Shipping Plan
I & T Plan
Calibration Plan
R.P. Johnson, UCSC
Status
Responsible
Draft
In progress
IPO
UCSC
Draft
Draft
Draft
Draft
Complete
Draft
UCSC
UCSC, SLAC
UCSC, SLAC
SLAC
Hiroshima, UCSC
SLAC
Draft
SLAC, UCSC
SLAC
UCSC, SLAC
INFN
UCSC
INFN
SLAC/INFN
Hiroshima
UCSC
INFN
SLAC
UCSC,SLAC,INFN
16
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Summary Tracker Schedule
Ac tivity
ID
Ac tivity
De scr i ption
Or ig Re m
E a r ly
Dur
S tar t
Dur
E a r ly
Finish
FY 00
FY 01
FY 02
FY 03
FY 04
FY 05
FY 06
Gamm a Ray Large Area Space Telescope
4.1 .4 TRAC KE R
S u btota l
1,3 28
03 /02/0 0A
07 /05/0 5
+ 4 .1.4. 1 TR A C K E R MA N A G E M E N T
0
12 /03/0 4
0
10 /05/0 4
+ 4 .1.4. 2 R E LIA B IL ITY & Q U A LI TY A S S U R A N C E
+ 4 .1.4. 3 TR A Y S U B -A S S E MB L Y
95 1
03 /02/0 0A
12 /24/0 3
85 3
08 /10/0 0
01 /23/0 4
65 3
02 /27/0 1
10 /08/0 3
55 9
10 /21/0 2
01 /26/0 5
13 1
11 /23/0 4
06 /07/0 5
19
06 /08/0 5
07 /05/0 5
+ 4 .1.4. 4 TO W E R S TR U C TU R E & A S S E MB LY
+ 4 .1.4. 5 TR A C K E R TE S T & C A LIB R A T IO N
+ 4 .1.4. 7 IN S TR U M E N T IN T E G R A TI O N & TE S T ( S LA C )
+ 4 .1.4. 8 M IS S I O N IN TE G R A TIO N & TE S T S U P P O R T
+ 4 .1.4. 9 M IS S I O N O P E R A TIO N S & D A TA A N A Y LY S IS
DRAFT
R.P. Johnson, UCSC
17
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Milestones
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Silicon-Strip Detector (SSD) Design Review
Tracker (TKR) Requirements Review
Tracker PDR
LAT Instrument PDR
Engineering Model (EM) assembly complete
Tracker CDR
LAT Instrument CDR
•
Qual Modules A & B Ready for Integration (for calibration unit) 05/15/03
•
Flight Modules 1 & 2 Ready for Integration (for calibration unit) 08/01/03
•
Flight Modules 3-16 Ready for Integration
R.P. Johnson, UCSC
01/29/01
03/07/01
05/30/01
08/06/01
01/20/02
05/29/02
08/05/02
10/01/03 – 12/24/03
18
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Preliminary Tracker Cost Estimate*
(Escalated K$)
4.1.4 Tracker
FY00
FY01
FY02
FY03
FY04
FY05
Total
SLAC
(DOE)
1389.0
1211.0
1520.5
3144.8
732.9
426.3
8424.5
UCSC
(DOE)
289.2
1070.2
417.3
260.0
269.1
234.8
2540.7
1678.3
2281.2
1937.8
3404.8
1002.0
Total
661.1 10965.2
*DOE/NASA funding.
R.P. Johnson, UCSC
19
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Tracker Issues
• Long lead time for procurement of 11,500 SSDs.
– The SSD design reviews have already been completed, and procurement of
flight detectors is in progress.
• Tight schedule for assembly of flight ladders and trays.
– Two industrial assembly lines are being set up in Italy, each with enough
capacity, in principle, to assemble all ladders and trays.
• ASIC design is the critical path for completion of the
engineering model.
– T&DF requirements demand extensive revision of both Tracker ASICs with
respect to the BTEM versions. SLAC engineers and an outside consultant
have been added to the effort to accelerate the pace of the design revisions.
• Thermal expansion, mass, and transparency issues place high
demands on the Tracker structural design.
– A solid plan has been worked out with Hytec Inc. to engineer and prototype
a simple panel structure based on carbon fiber, with good progress to date.
– A flexure design is in development for interfacing to the aluminum grid.
– An extensive test plan is in progress in Pisa to model and prototype the
converter and detector attachment for thermal testing.
R.P. Johnson, UCSC
20
GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Conclusions
• Beam tests and simulations have demonstrated that the Tracker
design based on silicon-strip detectors will meet (and exceed)
the LAT Science Requirements.
• The engineering efforts on the carbon-fiber structure, readout
electronics, and assembly tooling are on track to complete the
Tracker Engineering Model by CDR.
• A Tracker production schedule has been worked out that can
meet the LAT requirements by
– early procurement of SSDs,
– assembly of the readout electronics in U.S. industry,
– and assembly of the ladders and trays in Italian industry.
R.P. Johnson, UCSC
21