GlueX Start Counter Meeting, April 2, 2020

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GlueX Start Counter Meeting
Thursday, April 2, 2020
10:00 am EDT
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration and Efficiency (Rupesh)
  4. Dark Rate Studies (Beni, Rupesh, Tolga)
    1. Development of the Start Counter SiPM Dark rate over the Primex and Fall19 run period
      Sc dr ped.gif
      This is based on the pedestal data reported by the F250 firm ware running in raw mode unsparsified with no beam and random triggers.
  5. Action Item Review


Present: Rupesh Dotel, Tolga Erbora, Mark Ito, Simon Taylor, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site. Use your JLab credentials to gain access.

Review minutes from the last meeting

We went over the minutes from March 5 without significant comment.

Calibration and Efficiency

Rupesh showed counter-by-counter time resolution for the start counter after the propagation-time calibration. See his slides for the plots. At Sean's suggestion he tried applying constants obtained from run 71724 to data from run 71724 itself to see if there was a significant improvement over resolution using constants obtained from run 71003. Only slight improvement was visible.

The constants from run 71724 have been entered into the default CCDB variation for all of the Fall-2019/Spring-2020 run. Rupesh is looking at calibrating a few more runs dispersed throughout the run and applying them appropriately to smaller time periods of the run.

Dark Rate Studies

Beni showed the results from dark rate runs. See the plot below. The y-axis is the ratio of the area of a Gaussian fitted to the pedestal distribution, but using only the low side of the distribution, to the area of the entire pedestal distribution, as he described in a GlueX Doc from last year. The x-axis is accumulated coincidences from the pair spectrometer as a proxy for beam photon flux. Significant increase in dark current is seen.

Development of the Start Counter SiPM Dark rate over the PrimEx and Fall 19 run period. This is based on the pedestal data reported by the F250 firmware running in raw mode, unsparsified with no beam, taken with a random trigger.

Tolga has started reviewing Beni's code and will try to reproduce these results.

Action Item Review

  1. Obtained calibrations for sub-periods of the recent run. (Rupesh)
  2. Reproduce Beni's dark current results. (Tolga)