GLAST Large Area Telescope Engineering Meeting 23 November 2004 Charge Injection Calibration

1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope Engineering Meeting 23 November 2004 Charge Injection Calibration James Swain Stanford Linear Accelerator Center jswain@slac.stanford.edu 650-926-2721

2. Goal • To gather enough information to produce • DAC -> ADC curves for each discriminator in the front ends • Measurements of cross-talk between front end channels • Time over threshold curves • Need subsystem input • How should we collect TOT data? One channel at a time? • What pulse patterns do we need to make available? • FSW is proposing providing two pulse patterns, each of which can optionally be masked Engineering Meeting - Charge Inj. Calibration

3. Operation • Configure • Use LATC to perform initial configuration. • Perform reconfiguration (DACs, thresholds etc) within calibration loops as determined by LCI configuration files. • Pulse • Number of times determined by LCI configuration files • Read • Accumulate • Package • Preserve as much of the raw data as possible. • Send • Don’t Analyse • Don’t Apply Engineering Meeting - Charge Inj. Calibration

4. Calibration Styles Engineering Meeting - Charge Inj. Calibration

5. Calibration Styles (cont’d) • Bit scan • For charge injection DAC setting • For each of threshold setting • Pulse N times and record the number of accepts. • Simple version just uses a fixed number of DAC settings • Intelligent version focuses around the interesting threshold region. • ADC scan • Fixed number of injection DAC settings • Record ADC response to injection N times. Engineering Meeting - Charge Inj. Calibration

6. Volume and Time Estimates • Assumptions • Pulsing at 10 kHz • Pulsing 1 channel per TFE, 12 TFE per TRC • Cross-talk measurements will take longer • Auto-range readout for the CAL • Intend to use auto-ranging for most of the DAC values • Use four-range readout for overlap regions and keep two ranges so the overlap regions will increase data volume Engineering Meeting - Charge Inj. Calibration

7. FSW needs • What results would FSW like to be uploaded after calibration? • ACD pedestals • Might be nice, but not necessary • CAL linear correction • Two values per range per log end required. Engineering Meeting - Charge Inj. Calibration