Transcript ppt
GLAST LAT Project Gamma-ray Large Area Space Telescope Instrument Analysis meeting, April, 14, 2006 Calorimeter calibrations with Flight Software. Alexandre Chekhtman NRL/GMU A.Chekhtman 1 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 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 – – pedestals for ranges 0 and 1 (LE diode) - from events 5000-5999 Pedestals for ranges 2 and 3 (HE diode) • Settings for low energy diode and high energy diode are different » » 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 – A.Chekhtman May be we need to implement this procedure in calibGenCAL ? 2 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 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 A.Chekhtman 3 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 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 ? A.Chekhtman 4 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 Missing events – run 077002764 • • A.Chekhtman 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 5 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 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 A.Chekhtman 6 GLAST LAT Project Instrument Analysis meeting, April, 14, 2006 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 A.Chekhtman 7