Nov 2002T. Ljubicic DAQ100 Calibration Needs 10 to 8 bit (and back!) conversion table Gain correction per pad T0 correction per pad

Nov 2002T. Ljubicic 10  8 bit Conversion “TPC standard” tables exist (5 years old – R. Bossingham?) Need to make sure only one canonical copy exists in STAR! Main version is on daqman.starp.bnl.gov as /DAQ/include/adcLogTable.h Pseudo-logarithmic: –linear until 108, then logarithmic until 1023 Rough and not very “polished” but we used it from day-1 Relative conversion error (ΔCharge/Charge) < 1%

Nov 2002T. Ljubicic Gain Correction Gain correction per pad (“G”) is multiplicative i.e. –ADC corr = ADC raw * G G = 0.0 used to kill bad pads Obtained from pulser runs by summing up the ADC charge in the pulse (10 bit converted with pseudo-logarithmic table) 3 “regions” in the TPC: –Outer Sectors –Inner Sectors –Inner Sector on Sector 8 is special due to different pulser – not real gain! Method: –All pulses from many events for the 3 regions are histogrammed separately –G = 1.0 is by definition the charge at the peak of this distribution i.e. the most probable charge Relative Gain Correction!

Nov 2002T. Ljubicic T0 Correction Similar procedure as for the gain except all pads are used in the same histogram due to small differences sector-to-sector Method: Center-of-Gravity for all the ADCs above the ASIC cuts – same as done in the DAQ100 cluster-finder! The peak (most probable) value is by definition chosen to be 0.0 The values are in timebin coordinates (aka RHIC strobes) The correction is additive: –T corr = T raw + T0 Philosophy: –I think that there is no real T0 correction. –What we see is a slewing correction due to different pulse shapes of the electronics and the use of simple estimators (i.e. Center-of-Gravity). –Since the DAQ100 C.F. does the same COG we must correct for it in this same (statistical) way. –We should tune the pulser to look as much as possible as a MIP i.e. we need to lower the pulse!

Nov 2002T. Ljubicic “Production” Code exists and is running and is used (by me…) Some bad pads may be added by (Blair’s) hand if we feel it is necessary This canonical file will change rarely! Subsequent pulser runs will only be used to check against this file for changes (mostly to check against more bad pads…) but NO automatic updates!!! A G/T0 correction file exists for use in DAQ right now based upon the last pulser run 2 days ago… –/DAQ/conf/tpc_gains.txt We need to get this data into the “official” Offline databases