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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,_February_3,_2022#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">GlueX Start Counter Meeting, February 3, 2022,
</span><span class="mw-headline" id="Minutes">Minutes</span></h2>
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lang="en">
<p>Present: Mark Ito, Simon Taylor, Bo Yu, Beni Zihlmann
</p>
<p>There is a <a rel="nofollow" class="external text"
href="https://jlab-org.zoomgov.com/rec/share/FEYUyoVNo8VfRsNSvAqZMf2soMqdqWI9_Xaf4oqJr9HvTzaD01_H2qmw5pMdBU4B.pL6iuH51p-sNU86s">recording
of this meeting</a> on the ZoomGov site. The passcode
is #RFt51@4
</p>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_last_meeting">Review of
minutes from the last meeting</span></h3>
<p>We went over the <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_January_6,_2022#Minutes"
title="GlueX Start Counter Meeting, January 6, 2022">minutes
from the meeting on January 6th</a> without
significant comment.
</p>
<h3><span class="mw-headline"
id="Long-term_detector_maintenance_session_at_the_Collaboration_Meeting">Long-term
detector maintenance session at the Collaboration
Meeting</span></h3>
<p>We decided (by a majority of those present) that Beni
should give the talk, called for in <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/talks/2022/evaluating%20status%20of%20Hall%20D%20hardware%20and%20electronics.pdf">this
email from Matt Shepherd</a>, on Start Counter
maintenance at the February meeting.
</p>
<h3><span class="mw-headline" id="Dark_Rate_Test">Dark
Rate Test</span></h3>
<p>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.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:Sc_darkratetest_new.gif"
class="image" title="SC DarkRate Test"><img alt="SC
DarkRate Test"
src="https://halldweb.jlab.org/wiki/images/e/ec/Sc_darkratetest_new.gif"
width="698" height="474"></a>
</p>
<p>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.
</p>
<ul>
<li> 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.</li>
<li> We need to see if this increase in the noise
affects timing resolution.</li>
</ul>
<h3><span class="mw-headline"
id="Resolution_and_Calibration">Resolution and
Calibration</span></h3>
<p>Bo showed several validation plots from calibrations
Sean Dobbs has performed recently for the SRC run. See <a
href="https://halldweb.jlab.org/wiki/images/9/90/St_validation_srcct.pdf"
class="internal" title="St validation srcct.pdf">his
slides</a> 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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