Wednesday, November 13, 2019, 11:00 EST

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Back to Main Compton Page >> Compton Meetings

1. Dial Toll-Free Number: 1-888-240-2560 (U.S. & Canada)
2. International participants dial:
Toll Number: 1-408-740-7256
3. Enter meeting ID:140287970

Desktop sharing: 


Meeting room = Cebaf Center F227


  • Hall A will start earlier than originally planned - Monday, November 25
  • Hall will be locked up for high current test Wednesday or Thursday

Electron detector

  • Detector installation
    • motion ok
    • noise from Analog boards about +/-5 mV
    • might be issue with plane A (2uA) and D (12uA), plane B 25 nA, meter for thick plane might have died from radiation
    • adapters still need to be done
    • VXS crate installed with VETROC, VTP installed, need to configure NFS mounts to work
    • almost ready to look at cosmics
  • QWAD adapter boards
  • Counting DAQ


  • Mirrors replaced
  • Entrance scans
  • Cavity birefringence scans
  • Polarization strategy

Photon Detector

  • PREX checks - complete (?)
  • CREX preparations


  • ACC0 - laser-cycle analysis
  • ACC4 - laser cycle analysis


  1. Electron Detector
    1. Motion is working
    2. Adaptors for cables to VETROC will take 2 weeks
    3. QWAD adaptor boards ordered
    4. Counting DAQ crate now in hall
  1. Laser
    1. Entrance function has large residuals even after controlling back-reflections from rotating plates. The artifacts are for high DOLP at cavity entrance, but only for 2 of the four QWP settings.
    2. Polarization measured on back side of the cavity (locked in air at low power) has lower DOCP than observed previously. Is this caused by birefringence in the mirror surface (i.e. affects cavity polarization) or in the mirror substrate (only affects transfer/exit function)? This might be something worth testing by playing with the mount. Note: changing input mount would change entrance function.
    3. Mark: Have the entrance functions changed with time? See for example elog 368,elog 369 ,elog 436, elog 442 where there is no (little) wiggle with QWP.
  1. Photon detector
    1. 16 mV constant LED during LED linearity tests.
    2. No spare PMT available. Much discussion on what to do about this. PREX tube will be backup.
      1. This requires that we complete linearity tests over full range of ADC signal that was used in PREX.
      2. In addition find the best tube at CMU and have that as a deep backup.