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<p>Folks,</p>
<p>Please find the minutes <a moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_October_15,_2020#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p>_________________________________________</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">Minutes, GlueX Start Counter Meeting, October
15, 2020</span></h2>
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lang="en">
<p>Present: Rupesh Dotel, Mark Ito (chair), Simon Taylor,
Beni Zihlmann
</p>
<p>There is <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/TU20bHTvLpq">a recording
of this meeting</a> on the BlueJeans site. Use your
JLab credentials to gain access.
</p>
<h3><span class="mw-headline"
id="Review_minutes_from_the_last_meeting">Review
minutes from the last meeting</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_20,_2020#Minutes"
title="GlueX Start Counter Meeting, August 20, 2020">the
minutes from August 20</a> without a lot of comment.
</p>
<h3><span class="mw-headline"
id="Calibration_and_Efficiency">Calibration and
Efficiency</span></h3>
<ul>
<li> Calibrations for the 2019-11 run period look to be
in good shape.</li>
<li> 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.</li>
</ul>
<h3><span class="mw-headline" id="Dark_Rate_Studies">Dark
Rate Studies</span></h3>
<p>Beni led us through <a rel="nofollow" class="external
text" href="https://logbooks.jlab.org/entry/3853505">his
recent log book entry</a> 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.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:Sctest_usesamples.gif"
class="image"><img alt="Sctest usesamples.gif"
src="https://halldweb.jlab.org/wiki/images/c/c3/Sctest_usesamples.gif"
width="598" height="374"></a>
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<p>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.
</p>
<h3><span class="mw-headline" id="Action_Item_Review">Action
Item Review</span></h3>
<ol>
<li> Document calibration procedure (Rupesh)</li>
<li> Reproduce Beni's dark current results. (Tolga)</li>
<li> Revisit Yi's study of SiPM annealing. (Mark, Beni)</li>
<li> Look up type of SiPMs used in start counter. (Mark)</li>
</ol>
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