CFT Calibration System Two fold calibration system Certify the proper connectivity of the fiber channels and read out chain and on-off status of the channels. Calibrate the response of the individual channels and the system from WLS fibers onwards. Calibration will be done using physics events, special pre-scaled triggers and special pulser calibration runs.
CFT Calibration System Characterization Done before turning on the system Find operating conditions at various background/luminosity levels Temperature, operating voltages, gain, threshold, efficiency, QE etc. System Monitoring MIP, pedestals, LED, charge injection, light injection during beam on and beam off conditions.
Pedestals Can be taken during the Abort gaps or During regular data taking (few chips at any given time) to take into account the rate dependent effects For part of the detector Must turn off zero suppression, can be done for individual chips Need to store mean, sigma and number of events. Set digitization threshold such that just 1% of the events are above the threshold.
Charge Injection Good for SVX and read-out chain after it. Can be taken during Abort gap As a special run or With pre-scaled calibration triggers(??) Can obtain SVX operating parameters and gain
Light Injection Good for testing system beyond VLPCs Can be taken between stores, to check the status of the individual channels and time stability of the system. If the LED system is stable over the time, LED’s can be flashed during the regular data taking at various luminosities to evaluate the rate dependent effects (at higher rates, the QE, noise and gain of VLPC changes), which can be compensated by changing voltage.
Gain and Yield Gain determined by separation between peaks 13 ADC counts per femtocoulomb Typical Gain 40 000 Yield (pe.) N PE = (Average -Pedestal)/Gain
Threshold VLPCs at operating temperature (9 K) VLPCs at operating voltage (6.2-8.0 V) Pedestal run taken Large 0-pe peak, much smaller 1-pe peak Threshold set at 50kHz (Typically 1.2-1.6 pe)
Readout Can be done either with Primary DAQ path (if calibration done during the normal data taking with special runs/triggers) Or Through Secondary DAQ path, where data will be read and processed by the in- crate CPU card and shipped either to calib framework or remote computer for further processing.
Online Calibration Database All the calibration information including pedestals, gains, thresholds, fit parameters will go in the Oracle database. First pass design exists for the calibration and hardware databases… Need to take into account the needs of the offline calibration