Calorimeter calibrations with Flight Software. Gamma-ray Large Area Space Telescope Calorimeter calibrations with Flight Software. Alexandre Chekhtman NRL/GMU

Pedestals Previously pedestals were extracted from B13 runs with 4 range readout and zero suppression OFF With flight software we expected to get pedestals from standard configuration using events with 10 Hz periodic trigger Special trigger engine allows to read periodic triggers with 4 range readout and zero suppression OFF Now, due to some problem in FSW, periodic trigger is disabled Expected to be fixed in near future We use now another source of pedestals: run pedestal_ci_CPT This run collects 9000 events using solicited trigger with no charge injection for 9 different gain settings (1000 events per gain setting) Pedestal position and noise depend on gain setting Settings for low energy diode and high energy diode are different pedestals for ranges 0 and 1 (LE diode) - from events 5000-5999 Pedestals for ranges 2 and 3 (HE diode) For LAT71x (muon gain) - from events 8000-8999 For LAT701 (flight gain) – from events 7000-7999 For the moment pedestals from pedestal_ci_CPT were defined using IDL function and then merged manually May be we need to implement this procedure in calibGenCAL ?

Pedestal difference Difference of pedestals defined from B13 run 135005339 (Jan 14,2006) and from pedestal_ci_CPT run 077 002768 (Apr 11,2006) Pedestal difference in range 0 is ~3 adc unit = 0.1 MeV

Charge injection calibration Charge injection calibration with flight software works much slower (by factor of ~5) Standard columnwise charge injection run takes now 2 hours We decided to use broadcast charge injection pulse all calorimeter channels simultaneously This decreases the time and file size by factor 12 We should verify that the result of calibration stays unchanged Even with 100 Hz pulsing rate we afraid of missing events We have no information in the digi root file on the moment when DAC setting (injected charge) changes we just count events (50 events per DAC setting) If some events are lost, we have to use another way to separate events corresponding to different DAC settings Find peaks on ADC histogram ?

Missing events – run 077002764 Plot of Adc signal vs event number shows that the change of DAC setting happens exactly as expected at event =50*N So, there is NO missing events

Columnwise vs broadcast Difference between columnwise and broadcast charge injection calibration is less than 0.5% This plot produced by IDL without any protection against outpiers Peaks at some points are due to coincidence with scintillation in some events Should be suppressed by existing outlier protection in calibGenCAL

To be done next Modify calibGenCAL to work with broadcast charge injection files Zach has done it but not tested yet Process LAT71x files to get muon calibration (asym, MeVperDAC) Implement in calibGenCAL the processing of flight gain charge injection files, to get correct calibration for flight gains. Take into account LE to HE crosstalk