GLAST Large Area Telescope Gammaray Large Area Space

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GLAST Large Area Telescope Gamma-ray Large Area Space Telescope Engineering Meeting 23 November 2004

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

Goal • To gather enough information to produce – DAC -> ADC curves for

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 2

Operation • Configure – Use LATC to perform initial configuration. – Perform reconfiguration (DACs,

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 3

Calibration Styles Subsystem Calibrations ACD PHA (ADCs) CNO Accepts Hits Pedestals CAL TKR 23

Calibration Styles Subsystem Calibrations ACD PHA (ADCs) CNO Accepts Hits Pedestals CAL TKR 23 November 2004 Bit scan ADC scan X X X ADCs Low Energy Trigger High Energy Trigger Accepts Pedestals X X X Accepts Time over Threshold X X Engineering Meeting - Charge Inj. Calibration 4

Calibration Styles (cont’d) • Bit scan – For charge injection DAC setting – For

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 5

Volume and Time Estimates Subsystem Projected Time Uncompressed Volume CAL 10 s 420 Mbits

Volume and Time Estimates Subsystem Projected Time Uncompressed Volume CAL 10 s 420 Mbits 150 Mbits TKR 640 s 8 440 Mbits 420 Mbits ACD 10 s 30 Mbits 10 Mbits • Assumptions – Pulsing at 10 k. Hz – 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 23 November 2004 Engineering Meeting - Charge Inj. Calibration 6

FSW needs • What results would FSW like to be uploaded after calibration? –

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. 23 November 2004 Engineering Meeting - Charge Inj. Calibration 7