Wednesday, December 4, 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


  • Still need survey report for laser table --> update BPM offsets

Electron detector

  • Detector status
    • work on noise with Jinlong, maybe one bad board was causing problem, a few hot strips but most rates disappear with high threshold
    • added additionnal network switch
    • added network scope of analog signal
    • web cam for detector motion and dark current readout
    • not sure if we can fix the hot strips easily, needs to decable both side at the same time
    • to do
      • test FSD with magnets on
      • shielding scope / switch
      • From Dave estimates at 2.2 GeV : Compton Edet 14.8 mm, zero crossing 7.6 mm ( I think we can go as close as 5 mm from beam, so expect about 40 strips for Compton signal
  • QWAD adapter boards
  • Counting DAQ


  • Cavity status
  • DOCP in cavity

Photon Detector

  • CREX preparations


  • Too busy for analysis!


  1. General
    1. Hall C will not be ready for spin dance Friday. The soonest Hall C can support the RF stress test is Friday.
    2. Survey of Laser table not available yet. Once it's available, update BPM offsets.
  2. Electron Detector
    1. Most of the strips are "working", noise seems under control. Only 2 planes working right now. Ben needs to develop firmware to use all 4 planes.
    2. Adaptor boards are on their way with Michael.
    3. Have 2 good QWADs and we need 2 more. Will wait to see good output before cannibalising the Hall C system.
    4. Counting DAQ. Using VTP now. Working on timing and scalers using noise signals. Concern about correlated noise.
  3. Laser
    1. Locked a couple of days ago. Remote realignment was necessary, gain was the same but there was less input power. Total of 1.9-2.0 kW stored power. When the laser is first turned on there is about 800 mW which drifts down by ~10% over ~20 minutes.
    2. DOCP. Ideal solution in the cavity is close to minimum returning power.
  4. Photon Detector
    1. Completed last linearity test for the moment. Done at 100%, 90%, 70% and 50% of the expected gain. Relatively insensitive to gain (0.85% to 1.15% but not smoothly.) Nonlinear "dark delta" correction applied.
      1. Could the "dark delta" be gain dependent?
    2. Timing diagram. Need more information to connect the diagrams. Include HAPPEX timing board.
  5. Analysis
    1. Online analysis for CREX needs a location. Copy the main analysis and move to the PREX partition.