[Halld-pid] Start Counter Meeting Minutes, October 15, 2020

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_October_15,_2020#Minutes> 
and below.

   -- Mark

_________________________________________


    Minutes, GlueX Start Counter Meeting, October 15, 2020

Present: Rupesh Dotel, Mark Ito (chair), Simon Taylor, Beni Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/TU20bHTvLpq> on the BlueJeans site. Use your 
JLab credentials to gain access.


      Review minutes from the last meeting

We went over the minutes from August 20 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_20,_2020#Minutes> 
without a lot of comment.


      Calibration and Efficiency

  * Calibrations for the 2019-11 run period look to be in good shape.
  * The group reminded the chair that the overall quality of the start
    counter data is monitored by the group that Sean Dobbs has organized
    to look at monitoring histograms. Rupesh is part of the team
    responsible for the start counter plots.


      Dark Rate Studies

Beni led us through his recent log book entry 
<https://logbooks.jlab.org/entry/3853505> showing final results from his 
analysis of the "dark rate" runs taken to date. See the plot below. The 
downward slope indicates an increase in the dark rate as a function of 
time.

Sctest usesamples.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Sctest_usesamples.gif>

We had a brief discussion of how to judge this data and possible 
degradation of the performance of the start counter in general. Rupesh 
has reported a slight increase in timing resolution, at the 10% level, 
over the years. Simon reminded us of the spec of 350 ps for timing 
resolution; that is a relevant benchmark.


      Action Item Review

 1. Document calibration procedure (Rupesh)
 2. Reproduce Beni's dark current results. (Tolga)
 3. Revisit Yi's study of SiPM annealing. (Mark, Beni)
 4. Look up type of SiPMs used in start counter. (Mark)


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