Transcript ppt
GLAST LAT Project Gamma-ray Large Area Space Telescope Instrument Analysis meeting, July 28, 2006 Calibration of high energy diode. Alexandre Chekhtman NRL/GMU A.Chekhtman 1 GLAST LAT Project Instrument Analysis meeting, July 28, 2006 Problem with energy reconstruction above 1 GeV/crystal • No reconstructed energy depositions above 1 GeV for data collected with flight gain A.Chekhtman 2 GLAST LAT Project Instrument Analysis meeting, July 28, 2006 Calibration process for high energy diode • • When high energy diode is calibrated with muons, preamplifier gain is set to the value 10 times bigger, than normal (“muon” gain) Calibration includes two components: – adc2dac (integral nonlinearity) – relationship between measured signal (in ADC units) and the charge injected to the preamplifier input • Should take care of different preamplifier gain – MeVPerDAC – relationship between deposited energy in a crystal and the charge (in DAC units) injected to the preamplifier input • • • Should NOT depend on preamplifier gain In this simplified model to take into account the different preamplifier gain setting we just have to use the appropriate adc2dac calibration (for flight gain or for muon gain) Real situation is more confusing: we also can change the charge corresponding to one DAC unit by switching charge injection capacitor (controlled by CALIBGAIN bit in the configuration word) – We use CALIBGAIN=OFF setting when doing charge injection calibration with muon gain, otherwise the step of charge injection calibration would be too big, compare to muon signal • • • A.Chekhtman This setting decrease the value of one DAC unit by factor ~9.3 (CALIBGAIN factor). to take this into account, we have to multiply MeVPerDAC values by this CALIBGAIN factor, when reconstructing data collected with flight gain CALIBGAIN factor could be defined individually for each channel, by comparing charge injection calibrations done with CALIBGAIN=ON and CALIBGAIN=OFF 3 GLAST LAT Project Instrument Analysis meeting, July 28, 2006 Modifications to calibGenCAL • • • • • • ciFit will be able to process data for low energy diodes and high energy diodes separately ciFit for high energy diodes will be run 3 times with different runs from calibGen suite, producing 3 intnonlin files: 1. 2. 3. Muon gain, CALIBGAIN=OFF (calibGen run 204) Flight gain, CALIBGAIN=ON (calibGen run 102) Flight gain, CALIBGAIN=OFF (calibGen run 104) – – compare intnonlin files from 2 and 3 and will generate the file with CALIBGAIN factors for all channels. Generate MeVperDAC and Asymmetry files for flight gain – – For muon gain: intnonlin file 1 and MeVperDAC/Asymmetry for muon gain For flight gain: intnonlin file 2 and MeVperDAC/Asymmetry for flight gain Intnonlin file 1 will be used in muon calibration procedure when producing MeVperDAC and Asymmetry files for muon gain New python script will We have to store in the calibration database two sets of calibration files for each time period (with different “flavor”): When running reconstruction we should select appropriate calibration flavor, depending on configuration used for data collection. A.Chekhtman 4 GLAST LAT Project Instrument Analysis meeting, July 28, 2006 Status • Zach Fewtrell started to implement the proposed modifications beginning of this week • He hopes to get them ready today or on Monday • He’ll produce the new set of calibration files (for flight gain) for CU beginning of next week. A.Chekhtman 5