GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 1C: On-Orbit Calibration and Test

1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 1C: On-Orbit Calibration and Test Bill Atwood Santa Cruz Institute for Particle Physics University of California at Santa Cruz atwood@scipp.ucsc.edu

2. Initial Turn On Loading the Control Registers - Setting the Trigger Masks - Setting the Data Masks - Setting the Read Control Chip Ranges - Setting the Thresholds DACs Reading Back the Registers - Test for consistency Calibration Run - Setting the Charge injection masks - Setting the Charge injection DACs - Cycling through Threshold settings - Record the number of hits from each channel - Compare with results obtained prior to launch Noise Occupancy Check - Fire random trigger - accumulate counts per channel distribution - check for new noisy channels

3. First Triggers Enable 3-In-A-Row trigger - Accumulate cosmics into online monitoring histograms - Check Rates – look for noisy layers / towers

4. 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. Hit Strip Distributions - 884736 channels - 2 bytes/channel ( 2 MB storage) 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).

5. Monitoring House Keeping Data - Voltages - Temperatures (18 per tower – 2 per cable) - Read how often? Distributions dump to ground along with the data.