GLAST Large Area Telescope Engineering Meeting 23 November 2004 Charge Injection Calibration James Swain Stanford Linear Accelerator Center Gamma-ray Large Area Space Telescope

23 November 2004 Engineering Meeting - Charge Inj. Calibration 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

23 November 2004 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

23 November 2004 Engineering Meeting - Charge Inj. Calibration 4 Calibration Styles SubsystemCalibrationsBit scanADC scan ACDPHA (ADCs) CNO Accepts Hits Pedestals XXXXXXXX X CALADCs Low Energy Trigger High Energy Trigger Accepts Pedestals XXXXXXXX X TKRAccepts Time over Threshold XXXX

23 November 2004 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.

23 November 2004 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 SubsystemProjected Time Uncompressed Volume Compressed Volume CAL10 s420 Mbits150 Mbits TKR640 s8 440 Mbits420 Mbits ACD10 s30 Mbits10 Mbits

23 November 2004 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.