[Halld-pid] Start Counter Meeting, February 3, 2022

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_February_3,_2022#Minutes> 
and below.

   -- Mark

      _________________________________


    GlueX Start Counter Meeting, February 3, 2022, Minutes

Present: Mark Ito, Simon Taylor, Bo Yu, Beni Zihlmann

There is a recording of this meeting 
<https://jlab-org.zoomgov.com/rec/share/FEYUyoVNo8VfRsNSvAqZMf2soMqdqWI9_Xaf4oqJr9HvTzaD01_H2qmw5pMdBU4B.pL6iuH51p-sNU86s> 
on the ZoomGov site. The passcode is #RFt51 at 4


      Review of minutes from the last meeting

We went over the minutes from the meeting on January 6th 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_January_6,_2022#Minutes> 
without significant comment.


      Long-term detector maintenance session at the Collaboration Meeting

We decided (by a majority of those present) that Beni should give the 
talk, called for in this email from Matt Shepherd 
<https://halldweb.jlab.org/talks/2022/evaluating%20status%20of%20Hall%20D%20hardware%20and%20electronics.pdf>, 
on Start Counter maintenance at the February meeting.


      Dark Rate Test

Beni showed the latest version of his analysis of dark rate in the start 
counter as a function of time. The figure is shown below.

SC DarkRate Test 
<https://halldweb.jlab.org/wiki/index.php/File:Sc_darkratetest_new.gif>

The ratio plotted is the average of the ratios from the 30 start 
counters. The individual counter ratio is that of the area of a Gaussian 
fit to the pedestal distribution using only the low-side of the 
distribution to the total number of counts in the distribution. The 
Gaussian fit is insensitive to the high-side tail and thus 
underestimates the area of the pedestal distribution. The more area 
contained in the high-side tail, the lower the ratio.

  * There is no recovery of the dark rate between runs according to
    these data. Yi Qiang had seen some recovery in the SiPMs he tested.
  * We need to see if this increase in the noise affects timing resolution.


      Resolution and Calibration

Bo showed several validation plots from calibrations Sean Dobbs has 
performed recently for the SRC run. See his slides 
<https://halldweb.jlab.org/wiki/images/9/90/St_validation_srcct.pdf> for 
the plots. He showed timing offsets and resolution as a function of run 
number averaged over all counters as well as those for the individual 
counters. He also includes a list of problem runs that need further 
investigation.
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