CFT Calibration

Calibration Workshop

• Calibration Requirements

• Calibration Scheme

• Online Calibration databases

CFT Calibration System

Two fold calibration systemCertify 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 CharacterizationDone before turning on the systemFind operating conditions at various

background/luminosity levels• Temperature, operating voltages, gain, threshold,

efficiency, QE etc.

System MonitoringMIP, pedestals, LED, charge injection, light

injection during beam on and beam off conditions.

Pedestals

Can be taken during the Abort gaps orDuring regular data taking (few chips at any

given time) to take into account the rate dependent effectsFor part of the detectorMust turn off zero suppression, can be done for

individual chipsNeed 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 gapAs a special run orWith pre-scaled calibration

triggers(??)Can obtain SVX operating parameters

and gain

Light Injection

Good for testing system beyond VLPCsCan 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.

Rate Effects

Rate Effects

Gain and Yield

• Gain determined by separation between peaks

• 13 ADC counts per femtocoulomb

• Typical Gain 40 000

• Yield (pe.) NPE =

(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