Transcript Section 7.F - On Orbit CAL

GLAST LAT Project
March 24, 2003
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
Tracker Subsystem
WBS 4.1.4
7F: On-Orbit Calibration and Test
Bill Atwood
Santa Cruz Institute for Particle Physics
University of California at Santa Cruz
[email protected]
7F
Tracker Peer Review, WBS 4.1.4
1
GLAST LAT Project
March 24, 2003
Relevant Documents
• Applicable LAT documents to this review:
– LAT-TD-00249 - Tracker Front-end Readout ASIC Wafer Test Procedure
– LAT-TD-00248 - Tracker Readout Controller ASIC Wafer Test Procedure
– LAT-TD-00249 - Tracker Multi-Chip Module Test Plan
These Plans are in a formative state – This report is meant to convey our present
thinking only.
7F
Tracker Peer Review, WBS 4.1.4
2
GLAST LAT Project
March 24, 2003
Logic Functionality
GLAST Tracker Front End ASICs are a specialized, programmable
“computer.”
Two ASICs GTFE (analog and digital sections)
GTRC (digital section only)
Functional Testing Developed as part of parts testing during construction
Load & Read-Back Control Registers & DAC Settings
(TEM
GTRC
GTFE)
- Trigger Masks
- Data Masks
- Threshold DAC’s & Charge Calibration DAC’s
7F
Tracker Peer Review, WBS 4.1.4
3
GLAST LAT Project
March 24, 2003
Analog Testing
Calibration Run
- Setting the Charge Injection Masks
- Setting the Charge Injection DACs
- Cycling through Threshold DAC settings
- Record the number of hits from each channel
- Compare with results obtained prior to launch
Example from First Tests
of Flight GTFE Flight Chips
100
Channel C77
80
SigFit = 3.17
Mean = 32.45
Sigma = 5.97
60
For On Board Testing – a linear
fit to the transistion Region would
be made and the results sent to
the ground.
40
20
0
0
10
20
30
40
50
THR
7F
Tracker Peer Review, WBS 4.1.4
4
GLAST LAT Project
March 24, 2003
Analog Testing
Noise Occupancy Check
- Fire random trigger
- Accumulate counts per channel distribution
- Check for (new) noisy channels
Example from Mini-MCM Testing
Lines are the average channel noise
For each of the 6 chips (one SSD
Ladder’s worth)
Shows threshold setting corresponding
to ¼ MIP.
7F
Tracker Peer Review, WBS 4.1.4
5
GLAST LAT Project
March 24, 2003
Online Monitoring
Output from Tracker is minimal:
1) Address of an SSD channel indicating the presence of the
passage of a charged particle through the active area associated
with it (i.e. a “hit”)
2) The address of each X & Y plane of silicon strip detectors with
the collective OR of all the strips in that plane set - used for
triggering
3) Time-over-threshold (TOT) for the entire layer – for the OR’d
signal. This time is correlated with the amplitude of the largest
single SSD single in that layer.
7F
Tracker Peer Review, WBS 4.1.4
6
GLAST LAT Project
March 24, 2003
Online Monitoring
Hit Strip Distributions
- 884736 channels - 2 bytes/channel ( 2 MB storage)
- Expect: ~ 200 counts/channel/orbit (3900 counts/ch/day)
Layered OR Distributions
- 1152 Layered OR’s (all GFRC working) – 4 bytes/channel (4.5 KB storage)
Tower Trigger Distributions
- 16 Towers – which initiated the trigger
TOT Distributions
- 1152 channels – keep mean and RMS for each ( 9 KB storage).
7F
Tracker Peer Review, WBS 4.1.4
7
GLAST LAT Project
March 24, 2003
Online Monitoring
House Keeping Items (Periodically read, monitored & downlinked)
- Temperatures (18 Thermistors per Tower)
- Voltages (SSD Bias, various Analog & Digital supply voltages)
7F
Tracker Peer Review, WBS 4.1.4
8
GLAST LAT Project
March 24, 2003
Alignment
High energy cosmic rays (mostly protons at several GeV)
produce straight trajectories in GLAST
Boot-Strap proceedure
- Fit 3D straight lines to Tracker Hits
- Off-sets in Fit Residuals
tray-to-tray alignment off-sets
- Linear Dep. Of Fit Residuals
tray-to-tray rotations
Align Trays within Towers
Align Towers-to-towers
Procedure being developed in conjunction with I & T
( H. Tajima et al)
7F
Tracker Peer Review, WBS 4.1.4
9
GLAST LAT Project
March 24, 2003
Turn-on and First Triggers
- Perform Logic Check-out and Test
- Perform Analog Check-out
- Enable 3-In-A-Row trigger
- Accumulate cosmics into online monitoring histograms
- Check rates
- Select MIP subset to downlink (for alignment checks)
- Enable Gamma Triggering & Filtering
- Initial Operation may toggle between “gamma” data and
“straight-through” cosmic ray data.
- Helpful to have capability of several downlinks/day during
this phase.
7F
Tracker Peer Review, WBS 4.1.4
10