[Halld-pid] Start Counter Meeting Minutes, December 9, 2021

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_December_9,_2021#Minutes> 
and below.

   -- Mark

      ______________________________


    GlueX Start Counter Meeting, December 9, 2021, Minutes

Present: Eugene Chudakov, Mark Ito, Igal Jaegle, Simon Taylor, Beni 
Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/3xt7NebOwNA> on the BlueJeans site. Use your 
JLab credentials to gain access.


      Review of minutes from the last meeting

We went over the minutes from the meeting on October 14th 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_October_14,_2021#Minutes> 
without significant comment.


      Run report

Beni showed evidence of increased dark noise in the SiPMs. He looks at a 
statistic that is sensitive to a high-side tail of the pedestal 
distribution taken from beam-off data in raw mode. The higher the dark 
noise, the lower the statistic. This measure was explained at a previous 
start counter meeting 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_March_21,_2019#SiPM_dark_rate_measurement>. 
There is a clear trend, year-to-year, of increased dark noise.

Paddle response p1.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_response_p1.gif>
Pedestal distributions showing high-side tails.

Sc darkratetest.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Sc_darkratetest.gif>
Statistic as a function of run number

We discussed possible ameliorations, including replacing the SiPMs. We 
are nowhere near deciding on that course of action; more study is needed.


      Calibration

Mark will try to round up some volunteers to calibrate the start counter 
for the PrimEx and SRC runs.

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