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Background Sensors and Monitoring

PEP-II Liaison Training
31 March 1999
Terry Geld

Why do we need the background sensors?

  • Background Tuning: we need to measure backgrounds after injection and use the monitoring devices to tune backgrounds to acceptable level before bringing BaBar fully online.

  • Background Monitoring: we need to measure backgrounds on various time scales to determine if we are, e.g., too high at this minute for useful data; too high on average this day/week/month to sustain this dose rate to the SVT, EMC, DCH.

  • Background experiments: we need independent monitors available during dedicated background running when sensitive sections of BaBar may be off.

The background sensors for BaBar

  • PIN Diodes
    • Stanford, SLAC
    • 12 PIN diodes
      • continuously read out via analog abort modules
      • continuously read out via SVTRAD abort modules
      • raw currents (damage, dose rates, temps) sampled at fast and slow (7.5Hz) rates (via EPICS)
      • monitor each interlock channel for time to trip (via EPICS)

  • SVT
    • David Kirkby et al.
    • 12 Layer-1 half detector modules
      • leakage currents monitored via CAEN supplies when detector is biased (during data taking only) via CAENnet interface to EPICS
    • 12x14 Layer-1 AToM chips
      • per strip occupancies accumulated in ROM's and available in real time, via TCP/IP into EPICS
      • parameters sensitive to accumulated radiation damage extracted from each threshold-scan calibration and archived in conditions database
    • occupancies in depleted mode?

  • DCH
    • Aaron Roodman, et al.
    • long term radiation dose monitoring at electronics via RADFET's (into EPICS)
    • 4 PIN diodes (probably with small CsI button to increase sensitivity) ganged together with output via analog abort module to MCC
    • current drawn by each power supply monitored via CAEN/EPICS (will regang power supply cables to increase maximum current draw to 80uAmps); need to determine a "tuning" voltage where current is sensitive enough to bkg so currents can be used during beam tuning
    • DCH occupancy
      • @safe HV => for tuning, requires some change to e.g., runnable state definition
      • @full HV => for monitoring during data running

  • DIRC
    • Bob Wilson, Guy Wormser, Georges Vasileiadis, et al.
    • single discriminated PMT's per DFB ==> 2 per sector
    • rate from one PMT will go into FVC and sent via SAM to MCC
    • rate from one PMT per sector into gated scaler via EPICS
    • power supply current draw for 16 PMT groups via CAEN/EPICS

  • EMC
    • Adrian McKemey et al.
    • long term radiation dose monitoring via RADFET's (EPICS)
    • ganged diode dark currents via CAEN/EPICS
      • 8 quadrants in barrel
      • 2 halves in endcap
    • 4 PIN diodes with small CsI button to increase sensitivity ganged together via RADMON-like module; output via analog abort module to MCC

  • IFR
    • Henry Band, Jim Johnson, Pigi Paolucci
    • current draw via CAEN/EPICS (but temp effects probably dominate)
    • 2 1m**2 RPC's (back/forward) with 2 FEcards each going to 4 scaler channels; monitor with 2s integration time via EPICS

There is a table of signals showing which tasks they address (Bkg tuning, monitoring or for experiments).

There is a table of signals showing whether they are hardwired analog signals or via EPICS variables, along with readiness state.

There is a table of EPICS signal names. Most detectors are still working on the final epics code and names.

This page is: /BFROOT/www/Detector/Backgrounds/tlgeld/liaison_monitor.html

This page is maintained by Terry Geld (

Last modified: Tue Apr 13 14:06:03 PDT 1999