Transcript ppt

GLAST LAT Project
July 19, 2005
Science Verification
Analysis and Calibration
GLAST Large Area Telescope
Eduardo do Couto e Silva
SLAC Jul 19, 2005
E. do Couto e Silva
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GLAST LAT Project
July 19, 2005
Science Verification Analysis and Calibration
•
Objectives
– Calibrate the LAT and characterize its performance prior to launch
– Maximize science return by optimizing instrument capabilities
– Understand systematic effects to extend science reach
– Provide input to Instrument Science Operations Center
– Develop calibration, monitoring and diagnostics tools to be exercised on-orbit
– Strengthen collaboration ties and disseminate knowledge across teams
– Instrument analysis workshops ( 5th meeting scheduled for Aug 29)
•
Data
– Cosmic ray secondaries and low energy photons
– Collected at several stages of the LAT integration
– Particle beam tests
– spare LAT modules (after instrument delivery)
– Sophisticated Monte Carlo simulations
– Comprehensive description of detector geometry and physics processes
•
Data Analysis
– Probe a large parameter space of the Large Area Telescope
– Search for hardware failures
– Debug software
– Learn about the operational characteristics of the instrument
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Secondary Cosmic Ray Showers
Muon candidates
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Work from
Anders Borgland (SLAC)
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Instrumental Capabilities
•
Energy Resolution requirements
– Calibrate Energy Scales
– Beam test
– Calibrate out non-linear
effects
•
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Pointing accuracy requirements
– Inter and Intra tower
alignment
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Calibrate Energy Scales
•
•
Muon candidates
– 11.2 MeV peak in CAL crystals
We are able to probe effects at the 2% level
– improved offline software
Work from
David Smith (Bordeaux, France)
Data
MC
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Intra Tower Alignment
Work from
Michael Kuss (Pisa, Italy)
the ideal tower
a horizontal shift
a vertical shift
a rotation
the real tower
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GLAST LAT Project
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Horizontal and Vertical Alignment
θ
X4
real
position
X3
X2
X1
X0
ideal
position
res = x + z · cot(θ)
horizontal displacement: 157m
Aligns:
• horizontal ( to strips)
• vertical
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vertical displacement: 81m
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Calibrations Work!
•
Effect is calibrated out for all planes
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GLAST LAT Project
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TKR Efficiencies
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Objective
– Measure and monitor trigger
efficiencies
Work from
Tsunefumi Mizuno et al (Hiroshima, Japan)
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– includes effects from
» Gap between Silicon wafers
» dead strips
» insensitive area
» alignment
» timing
Select muon candidates with TKR
– Define a track using 4 layers
– 3 top and 1 bottom
– Test intermediate layers
– Measure efficiency
– Compare with MC simulations
Tower
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– Direction and position
measured by TKR
» See next slide
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TKR Efficiencies: Data/MC Simulation
Tower in Pos#8
Tower in Pos#9
Good agreement between MC and Data
within 1% for all 6 towers
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GLAST LAT Project
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Timing of Integrated Systems
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Need to align TKR/CAL/ACD
– To trigger efficiently
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Need to align TKR/CAL/ACD
– To latch data efficiently
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On-orbit Operations
– Trigger alignment knobs are
controllable remotely
– We are currently acquiring
experience on the ground
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Minimizing the Effects of Trigger Jitter
Work from
Martin Kocian and Su Dong (SLAC)
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Mainly caused by pulse height
differences with respect to the trigger •
threshold
– TKR
Time-in of towers
– Optimize performance
– Uniformity across towers
– Large signals from CNO
– CAL
– Large variation in energy
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Time Between Events: Baseline Run
Work from
Warren Focke and Anders Borgland
(SLAC)
Expect 26.5 s
Good agreement!
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Probing Several Instrument Configurations
• We designed a series of tests in which we change only one
parameter in the instrument and
– Collect cosmic rays
– Select muon candidates
– Verify the behavior is not affected by parameter changes
• Example of parameters
– Read TKR from “right” or “left” cables only
– Change Voltage of Power Distribution Unit
– Overlay a source of high rate triggers on the top of existing
cosmic ray triggers
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No major discrepancies found so far…
From Stefano and Claudia (Perugia, Italy)
Change voltage
Baselin
e
●Min
●Max
●
From Monica Brigida (Bari, Italy)
Baseline (read from both
sides)
Right Readout only
Left Readout only
Bottom Plane = 0
Top plane = 35
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Plane
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Cosmic Ray Secondaries: Photon Candidates
Work from
Leon Rochester (SLAC)
and William Atwood (UCSC)
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Summary and Outlook
•
Summary of SVAC activities
– Focus on improving and updating calibrations
– Explore on-orbit operational aspects of the instrument
– As well as we can simulate on the ground
– Not part of PASS/FAIL testing
– Longer term feedback on instrument characterization
– Propose special tests as needed
•
Timeline
– Environmental Tests
– Data will be delivered to SLAC for offline analysis
– Focus on correlating housekeeping with science data
– Environmental dependencies of calibrations
– Spacecraft Integration
– On-orbit checkout
– First year of operation
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