GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
ACD Subsystem
Jonathan F. Ormes
ACD Subsystem Manager
Rudolph K. Larsen
ACD Project Manager
Laboratory for High Energy Astrophysics
NASA Goddard Space Flight Center
ormes@lheavx.gsfc.nasa.gov
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Anti-Coincidence (ACD) Subsystem
Outline
 Technical overview
 Requirements
 Status
 Organization
 Schedule
 Budget
 Technical issues and mitigations
 Summary
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Large Area Telescope (LAT) Design Overview
Instrument
16 towers  modularity
height/width = 0.4  large field-of-view
Tracker
Si-strip detectors: 228 mm pitch, total of
8.8 x 105 ch.
Calorimeter
hodoscopic CsI crystal array
 cosmic-ray rejection
 shower leakage correction
XTkr + Cal = 10 X0  shower max
contained < 100 GeV
Anticoincidence Detector Shield
segmented plastic scintillator
 minimize self-veto
> 0.9997 efficiency & redundant readout
3000 kg, 650 W
(allocation)
1.75 m  1.75 m  1.0 m
20 MeV – 300 GeV
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
ACD: The First Line of Defense Against Background
•
The purpose of the ACD is to detect incident cosmic ray charged
particles that outnumber cosmic gamma rays by more than 5 orders of
magnitude. Signals from the ACD can be used as a trigger veto or can be
used later in the data analysis.
•
Segmented plastic scintillator (Bicron-408) read with wave-shifting fibers
(BCF- 91MC) + PMT (Hamamatsu R1635, R4868) readout.
• Each segment (tile) has a separate light tight housing.
• Separate tile housings provide resistance to accidental puncture by
micrometeoroids.
• Wave-shifting fiber readout provides light collection uniformity
•
Gaps between tiles are deliberately misaligned with the gaps between
tracker towers and covered by scintillating fiber "tapes"
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Design Heritage
Backsplash reduced the EGRET effective area by 50% at 10 GeV compared to 1 GeV.
GLAST will be studying photons to above 300 GeV.
Anticoincidence Detector for GLAST is subdivided into smaller tiles to avoid the
efficiency degradation at high energy.


ACD
tracker
ACD
Dd
Tracker
calorimeter
EGRET
J. Ormes/R. Larson
CsI
calorimeter
0.2-2 MeV "backsplash" photons GLAST
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Design Approach
Lip to "hide" thermal blanket and micro-meteorite shield
Segmentation for side entry events
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Science Requirement: Efficiency
•
SRD Background Rejection requirement: Contamination of the high
latitude diffuse gamma rays by background in any decade of energy for >
100 MeV shall be less than 10%. The goal shall be 1%.
•
Charged particle background rejection involves the use of pattern
recognition in the tracker and the calorimeter as well as the ACD.
•
For protons, calorimeter and tracker are powerful.
•
•
105 : 1 at system level
Electrons are more problematic.
•
Electrons create showers in the calorimeter identical with photon
showers.
•
•
Worst case is 3 x 103 : 1 at 10 GeV
The required ACD efficiency for charged particles (detector efficiency +
hermeticity) is 0.9997
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Additional Requirements
• Tile segmentation
– Efficiency > 80% at 300 GeV relative to that at 1 GeV
– Effective area at >60o; >0.1 of on-axis value
• No more than 10% loss of effective area
– 6% in the plastic and structure
– 1% from ACD deadtime
– 1% loss from noise
– <5% chance of loss of tile in 5 years (electronics)
– <1% per year for loss of tile by micrometeoroid puncture
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Physical interface specifications
•
•
•
•
•
Mass
200 kg + 60 kg (30% reserve) = 260 kg
Electronics
34 kg + 17 kg (50% reserve) = 50 kg
Power
30 watts + 25 watts (80% reserve)
Volume - see materials presented by Martin Nordby
Electronic signals
– Fast VETO
• Pre-primitives for Trigger thresholds
• Hi Z trigger for calibration events
– Addresses of hit tiles
• Pulse heights of hit tiles
– Rate date from all tiles
– Housekeeping data
– Command, command verification, and control
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
ACD Technical Status
• Detectors:
• Scintillator tile light output tests have been performed.
• Tile overlapping and detector tapes are planned to cover gaps
• Electron background rejection analysis cuts being developed
• Side tile segmentation is being reevaluated
• Trade studies are being performed
• tile thickness, segmentation and PMT placement
• Electronics:
• ASIC development proceeding
– First prototype submission was in January
• Higher gain Hamamatsu PMTs are being evaluated
• Electronic parts have been submitted for acceptance
• High voltage power supply specs, SOW and cost estimate created
– Procurement for prototype sent to identified vendors
• Mechanical:
• Tile support structure has been improved over proposal design
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
ACD WBS Organization Chart
ACD Subsystem
4.1.6
Jonathan Ormes - Lead
ACD management
4.1.6.1
Rudy Larsen - Manager
Cristina Doria-Warner - Financial
Resources
Dennis Wicks - Scheduling
ACD Design and Science support
Alexander Moiseev,Lead
David Thompson, Robert Hartman
David Bertsch, Jay Norris
ACD Simulations
Heather Kelly
Taro Kotani
Alexander Moiseev
ACD Detectors
4.1.6.3
Alexander Moiseev, Lead
Robert Hartman
John Krizmanic
ACD Electronics
4.1.6.4
Dave Sheppard, Lead
S. Singh, ASIC design
Robert Baker
ACD Mechanical
Components
4.1.6.5
ACD Flight Software
4.1.6.6
Thomas Johnson, Lead
Sharon Seipel
Scot Murphy
Robert Schaefer, Lead
Electrical Test
Fabrication
Darrin Buck
James Odom
William. Daniels
Donald Righter
ACD System Engineering
Tom Riley
ACD Reliability and Quality Assurance
4.1.6.2
Patricia. Huber, Lead
Russell Murray, Quality
John Remez, Reliability
Peter Jones, Parts
Fred Gross, Materials
Bo Lewis, Safety
Reserved
4.1.6.7
Insrument
ACD Subsystem
Integration & Test
4.1.6.8
Mission Integration
& Test Support
4.1.6.9
John Lindsay, Lead
Tom Johnson
John Lindsay, Lead
Mission Operation
& Data Analysis
4.1.6.A
David Thompson, Lead
Micrometeroid Shield /
Thermal Blanket
4.1.6.B
Thomas Johnson, Lead
Lou Fantano, Thermal
Lead
Robert Hartman
All ACD team members above are GSFC civil service employees or GSFC contractors
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Contributing GSFC Lead Organizations
• WBS 4.1.6 ACD Subsystem - Dr. Jonathan Ormes, GSFC Code 600, Space Science Directorate
• WBS 4.1.6.1 ACD Management - Rudy Larsen, GSFC Code 700.1, Project Formulation
• System Engineering - Tom Riley, GSFC Code 730.4, Instrument Systems Office
• Science Support- Dr. Alexander Moiseev, GSFC/USRA Code 661, Gamma Ray and Cosmic
Ray Astrophysics Branch
• WBS 4.1.6.2 ACD Reliability and Quality Assurance - Patricia Huber, GSFC Code 303, Assurance
Management Office
• WBS 4.1.6.3 ACD Detectors - Dr. Alexander Moiseev, GSFC/USRA Code 661
• WBS 4.1.6.4 ACD Electronics - Dave Sheppard, GSFC Code 564, Microelectronics and Signal
Processing Branch
• WBS 4.1.6.5 ACD Mechanical Components - Tom Johnson, GSFC Code 543, Mechanical
Engineering Branch
• WBS 4.1.6.6 ACD Software - Bob Schaefer, GSFC/HSTX Code 664, Data Management and
Programming Office
• WBS 4.1.6.8 Instrument Subsystem Integration & Test - John Lindsay, GSFC Code 568, Flight
Systems Integration and Test Branch
• WBS 4.1.6.9 Mission I&T Support - John Lindsay, GSFC Code 568
• WBS 4.1.6.A Mission Operations & Data Analysis - Dr. Dave Thompson, GSFC Code 661
• WBS 4.1.6.B ACD Micrometeoroid Shield/Thermal Blanket - Tom Johnson, GSFC Code 543 /
Louis Fantano, GSFC Code 545, Thermal Engineering Branch
-----------------------------------------------------------------------------------------------------------------------------------USRA- University Space Research Association
EITI - Emergent Information Technologies Inc.
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
4.1.6 ACD Schedule
A c tivity
ID
A c tivity
D e scr i ption
Or ig
Re m
E a r ly
D ur
D ur
S tar t
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 .6 A N TI C OIN C ID E N C E D E TE C TOR
S u btota l
1,3 68
04 /03/0 0
09 /30/0 5
1,2 55
09 /12/0 0
09 /30/0 5
1,1 76
01 /11/0 1
09 /30/0 5
59 3
11 /07/0 0
04 /04/0 3
1,2 49
09 /12/0 0
09 /22/0 5
77 6
12 /01/0 0
01 /26/0 4
1,2 76
04 /03/0 0
05 /20/0 5
1,1 00
01 /11/0 1
06 /14/0 5
1,1 00
01 /11/0 1
06 /14/0 5
1,1 00
01 /11/0 1
06 /14/0 5
+ 4 .1.6. 1 A C D M A N A G E ME N T
+ 4 .1.6. 2 R E LIA B IL ITY & Q U A LI TY A S S U R A N C E
+ 4 .1.6. 3 A C D D E T E C T O R S
+ 4 .1.6. 4 E LE C TR O N IC S
+ 4 .1.6. 5 M E C H A N IC A L C O MP O N E N TS
+ 4 .1.6. 6 A C D FLIG H T S O F TW A R E
+ 4 .1.6. 8 IN S TR U M E N T A C D S U B -S Y S TE M I & T
+ 4 .1.6. 9 M IS S I O N IN TE G R A TIO N & TE S T S U P P O R T
+ 4 .1.6. B T H E R MA L B L A N K E T / MIC R O S H IE LD
INCOMPLETE
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
ACD Milestones
• ACD & Thermal Blanket Requirements Review
• ACD & Thermal Blanket PDR
• LAT Instrument PDR
• ACD & Thermal Blanket CDR
• LAT Instrument CDR
• ACD Engineering Model (EM) Complete
• ACD Flight Subsystem Assembly Complete
• Thermal Blanket / Micrometeoroid Shield Ready for Integration
(with thermal model)
• Delivery of Calibration Unit ACD to SLAC
• Flight ACD Ready for Integration
J. Ormes/R. Larson
03/21/01
06/27/01
08/06/01
06/26/02
08/05/02
05/15/03
10/01/03
02/01/03
05/15/03
01/26/04
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Interim ACD Cost Estimate*
(Escalated K$)
4.1.6 ACD
FY00
FY01
FY02
FY03
FY04
FY05
Total
GSFC
436.2
607.1
3036.1
3136.2
1929.8
390.7
9536.1
436.2
607.1
3036.1
3136.2
1929.8
390.7
9536.1
(NASA)
Total
*DOE/NASA funding.
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Technical Issues and Mitigations
• Increase technical margin for light collection
– Add reflective termination to fibers or read out at both ends
– Monitor and adjust PMT gain in flight
– Request 25-30 kg additional mass for thicker tiles on top
• Required volume for electronics may exceed available
– Place PMTs under ACD
– Place some of electronics underneath the grid
– Reduce side segmentation
• Parts acceptance and procurement
– Prototype HVPS procurement is in preparation
– Parts list submitted to Quality Assurance Branch
• Integration highly coupled to design
– ACD I&T manager appointed to work with design team
J. Ormes/R. Larson
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GLAST LAT Project
DOE/NASA Review of the GLAST/LAT Project, Feb. 13-15, 2001
Summary
• ACD team is in place and progress is quite rapid
– Necessary trade studies underway
• Optimization of side segmentation
• Optimization of redundancy
• Optimization of light collection; tile thickness
– Requirements have been established
• Near term schedule advanced
– Received additional funding for FY '01
– Added staff to prepare for PDR
– Draft Level 6 schedule is in hand
• Grass roots costing being scrubbed
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