Notes from Meeting May 01, 2009

• GSO Crystal

  • There was further discussion about the cause of a misidentification of laser ON/OFF bit documented on HAPLOG post 1598.
    • Related to quarter wave plate? Takes time to get proper values after changing plate.
    • Can we get independent cavity ON/OFF signals?

• Compton Electron Detector

  • Sirish posted first spectra taken with new detector on HALOG 270119.
  • Paul asked if we can look at conincidences between electron detector and GSO photon detector.
  • Bob talked about combining DAQ (fADC and detectors).

• Nonlinearity of PMTs at CMU

  • Megan reported nonlinearity reported on previously is real.
  • Bob suggested they use ND filters as part of study.
  • Nonlinearity was 15% for 6GeV. Want to make sure linearity is good for less than 3GeV, but they think it is.
  • There was a discussion about spectra taken during last run:
    • There were accumulator runs and Compton spectra taken ar all passes.
    • Lead/Tungsten spectra were very unstable... GSO better?
      • Diana noticed gain shifts which need to be quantified by analyzing data that is already available.
      • Also commented on whether the gain changes with rate. This could change widths in an unpredictable way.

• ADC Testing at JLab

  • TestCrate has been modified to handle multiple 18bit ADCs at a time. Further tests can now be conducted to make sure multiple 16bit and 18bit boards can coexist without problems.
    • Need to check for crosstalk and test at high rates.
    • Right now can get 3 18bit boards working together. When a 4th one is added, the crate crashes. Need to find the cause of the problem.

• Simulations

  • Talked about Dustin's HAPLOG post 1599
    • There is a difference in x-res for standard and new optics. The new one gives better resolution in both x and y. There was a 15% improvement for the x-res at the focal plane where the VDCs are.
  • Talked about Dustin's HAPLOG post 1600
    • Shows that y distribution is made narrow when x cuts are imposed. This will be explored further
    • Thicknesses bigger than 8.6% will shift backgrounds away from the elastic peak. Smallet thicknesses still leave some contamination.
    • Investigate rates - break up Be plug signals for best place to measure.
    
    
    Comments to: Bob Michaels