May 24, 2019 - PrimEx-Eta Meeting

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Time and Place

  • Time: Friday, May 24, 2019 2:00 pm EST.
  • Room: CEBAF Center, Room F227

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Status of CompCal Energy Calibrations

Status of the He target density monitoring


  1. CompCal Energy Calibrations
    • Drew updated on status of CompCal calibrations using the snake scan from the beginning of Spring RUn
    • The led signal integrals show periodic structure during snake scan.
      • There is a minimum in each cell's plot of the average led integral vs. snake scan run number when that cell is centered in the beam path, but the plots actually indicate that there are also local minima whenever the rows above and below the cell are centered in the beam path.
      • Will try to use CCAL scalars to see if this is a rate-dependent phenomenon, or if this could be induced by some other effect (e.g. polarity of the voltage on the CCAL motor when moving to the right vs. to the left)
    • When calibrating, use an LED correction factor based on the shift of the led amplitude from the first run of the scan.
    • A nonlinear correction was calculated using reconstructed showers. Because the showers incorporate multiple cells, its best to determine the shape of the nonlinearity on a channel-by-channel basis.
      • Drew will look at this non-linearity shape of the individual hits and determine a correction based off that.
    • There still exists a shift in the beam energy minus two shower energy.
      • For the FCAL, Colin should have some improved gain factors by sometime next week.
      • For the CCAL, this shift is likely due to the lack of an LED correction factor used. The difference of the LED signal integral between the snake scans and the production runs should be accounted for and will probably improve the calibrations. Drew will look at this and come up with an initial set of CCAL calibrations.
  2. Target Density Monitoring
    • Sasha showed a plot of the variations in the ratio of the start counter scalars to the PS scalars.
    • His plots show a very stable rate indicating a very stable target density.
    • The three flat regions in his plots are for 200 nA current, 50 nA current, and 100 nA current.