Fastbus ADC Pedestal Calibrations

The Fastbus ADC pedestals are obtained using the data obtained during dedicated pedestal runs or TOF cosmic runs. The value of the ADC pedestals varies between 200 to 800 ADC channels. For more details, please refer to the ADC manual.

The procedure used to calibrate the TDCs is as follows:

• Collect Fastbus data using cosmic triggers and a randomly generated trigger (note: no beam should be present during data collection).

• Set up the gain calibration super module. This is done by executing the following command:

.x $PHATHOME/phatplastic/macros/FBPedCalc_Setup.C

This command produces the following output:

::ListModules():
Module #0: TPhModule:FBGeoInitMod (Enabled)
Module #1: TPhModule: FBInitMod (Enabled)
Module #2: TPhModule: FBunpackerMod (Enabled)
Module #3: TPhModule: FBIndexMod (Enabled)
Module #4: TPhModule: FBPedCalcMod (Enabled)
Module #5: TPhModule: VerifyFBPedestalMod (Enabled)
Setup for Fastbus pedestal calculation completed successfully! 

• Run the super module. This is done by executing the following command:

  .x $PHATHOME/phatplastic/macros/FBPedCalc_SM.C(6219,0,"/data/cr01/data")

  where the arguments are:

  • run number (in this example 6219)
  • sequence number (in this example 0)
  • location of the data file (in this example /data/cr01/data)

   

  This command produces the following output:

  FBPedCalcMod(TPhFBPedCalcMod): High noise value for FB = 0 Slot = 23 Channel = 39 Sensor = TC52 Noise = 30.2832
  FBPedCalcMod(TPhFBPedCalcMod): High noise value for FB = 0 Slot = 23 Channel = 44 Sensor = TC54 Noise = 36.8543
  Finished!
  Number of events read = 1499
  Calibration objects are stored in object manager FBPedCalcModObjs
  VerifyFBPedestalMod(TPhVerifyFBPedestalMod): **** VERIFYING FASTBUS PEDESTALS
  VerifyFBPedestalMod(TPhVerifyFBPedestalMod): Accept? [y/n] 

  Before accepting the calibrations please look at the canvas created by this macro. The results of the analysis of run 6219 are included here.

  The canvas shows the two two-dimensional histograms (left) with the raw ADC data (top) and the pedestal subtracted ADC data (bottom). The two one-dimensional histograms (right) shows the extracted pedestals (top) and the pedestal noise (bottom). Four things needs to be checked:

  • All ADCs must respond (a total of 10 vertical bands should appear). The two trigger and ZDC ADC data are shown by the two vertical bans on the left-hand side of each histogram. The TOF ADC data are contained in the 8 vertical bands on the right-hand side of each histogram. If there are 9 or less vertical bands, an expert should be called.
  • A successful pedestal calibration should produce ADC spectra, with a pedestal peak centered at 0 (bottom left spectrum).
  • Pedestal values can vary between 200 ADC channels and 800 ADC channels (top right spectrum). Any value larger than 1000 or negative suggest problems with the pedestal determination procedure and/or problems with the ADC.
  • The pedestal noise (bottom right spectrum) should show noise value of less than 40 ADC counts.

• After examining the histograms displayed decide whether or not to accepts the calibrations. If you accept the calibrations, the calibration parameters will be written to the database. You will see the following information on the screen after accepting the calibration:

  VerifyFBPedestalMod(TPhVerifyFBPedestalMod): Authenticating TOF DB as phatwriter...
  VerifyFBPedestalMod(TPhVerifyFBPedestalMod): Writing FB Pedestals for Run, Seq #6219, 0
  VerifyFBPedestalMod(TPhVerifyFBPedestalMod): ...Revoking FB Database 
  Writing object manager to FBPedCalc006219s000.root
  FBPedCalc : Real Time = 901.27 seconds Cpu Time = 164.52 seconds
   

• All done!

Frank Wolfs, University of Rochester, June 2001