Wednesday, March 4, 2020, 2:00 pm 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 = Counting House Meeting Room


  • Compton position lock, orbit
  • Periodic low current runs
  • Decreasing photon detector rates [1]

Electron detector

  • Offsets and efficiency [2]
  • Helicity decoding [3], [4]
  • QWAD installation


  • Laser polarization systematic tests [5]
  • Low threshold vs. high threshold spectra at full and half gain (low current): [6]

Photon Detector

  • Spectrum fitting for collimator offset (low threshold, high threshold)


  • Online analysis results
  • Polarization vs. time


Mark, Michael G, Alex C, Bob M, Chip, Iris, Kent, Dave, Alex, JC, Amali,

  1. Photon Detector
    1. Adam did jaws test, 28 Feb.
      1. Jaws aperture at 8 mm (should let most through) but cut everything. Are jaws not aligned with collimator?
      2. Adam took pictures in access. Jaws center look look to be offset low by a few 4 mm. [7]
      3. Home position puts jaws in similar position to the finger (which see interactions.)
    2. Adam to show finger scan data at next meeting.
    3. Try running with jaws wide open for a run?
    4. Dropping accumulator size versus time (about 15% over a couple of weeks.) [8]
      1. Compton edge is same, so it's not gain change.
      2. Spot size change (we've seen changes at the target.) Study with vertical scan data.
    5. Polarization change with time. Dropped and then recovered with spot move. (Appears to be QE.)
    6. Study the spectrum with different gains and trigger thresholds. There appear to be issues at low energy which might be triggering on reflections. [9] Can randoms be used to help with this? Mark, Amali, JC will meet to discuss.
  2. Laser
    1. Gaskell found some options to study the laser polarization but needs to be repeated from different starting point.
  3. Electron Detector
    1. Discussions about noise on the detector.
    2. Running at block 1 leads to missed MPS triggers.
    3. Helicity decoding algorithm was confirmed.
  4. Analysis
    1. Polarization versus time plots.