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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,_March_21,_2019#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p>_____________________________________</p>
<p>
</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">Minutes, GlueX Start Counter Meeting, March 21,
2019</span></h2>
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<p>Present:
</p>
<ul>
<li> <b> JLab: </b> Sean Dobbs, Mark Ito (chair),
Simon Taylor, Beni Zihlmann</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/QISGJ/">recording of
this meeting</a> on the <a rel="nofollow"
class="external text"
href="https://jlab.bluejeans.com/">BlueJeans site</a>.
Use your JLab credentials to authenticate.
</p>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<p>The Start Counter NIM paper <a rel="nofollow"
class="external text"
href="https://mailman.jlab.org/mailman/private/gluex-collaboration/2019-March/005133.html">has
been published</a>. The record in JLab's publication
database has been updated as has the GlueX wiki's list
of publications.
</p>
<h3><span class="mw-headline"
id="Review_minutes_from_the_meeting_on_February_7">Review
minutes from the meeting on February 7</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_February_7,_2019#Minutes"
title="GlueX Start Counter Meeting, February 7, 2019">the
minutes</a>. Sean plans to talk to Mahmoud Kamel about
the status of the comparison between data and Monte
Carlo.
</p>
<h3><span class="mw-headline"
id="SiPM_dark_rate_measurement">SiPM dark rate
measurement</span></h3>
<p>Beni has analyzed data taken under the following
conditions
</p>
<ul>
<li> read-out threshold set below pedestal</li>
<li> read-out of all SiPM detector systems (start
counter, BCAL, etc.)</li>
<li> random trigger at 2 kHz</li>
<li> raw mode</li>
</ul>
<p>He integrates over all samples and normalizes to the
number of events. Histograms are fit to a Gaussian from
the low side to just over the peak on the high sides.
The idea is to count events in the high-side tail of the
distribution. The data from two runs are shown. The red
points were taken in the middle of the Beryllium target
run, the blue points are from yesterday. He showed some
representative channels from the start counter.
</p>
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<tbody>
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<td> <a
href="https://halldweb.jlab.org/wiki/index.php/File:H4.gif"
class="image"><img alt="H4.gif"
src="https://halldweb.jlab.org/wiki/images/thumb/d/de/H4.gif/300px-H4.gif"
width="300" height="204"></a>
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<td> <a
href="https://halldweb.jlab.org/wiki/index.php/File:H5.gif"
class="image"><img alt="H5.gif"
src="https://halldweb.jlab.org/wiki/images/thumb/8/85/H5.gif/300px-H5.gif"
width="300" height="204"></a>
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<td> <a
href="https://halldweb.jlab.org/wiki/index.php/File:H19.gif"
class="image"><img alt="H19.gif"
src="https://halldweb.jlab.org/wiki/images/thumb/b/b2/H19.gif/300px-H19.gif"
width="300" height="204"></a>
</td>
<td> <a
href="https://halldweb.jlab.org/wiki/index.php/File:H20.gif"
class="image"><img alt="H20.gif"
src="https://halldweb.jlab.org/wiki/images/thumb/6/63/H20.gif/300px-H20.gif"
width="300" height="204"></a>
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<p>He believes that there is an effect seen, but more
analysis is needed.
</p>
<p>Beni wants to talk to Carl Zorn about what expectations
for dark rate are. Also he has yet to look at other
detector systems.
</p>
<p>He also mentioned that there is a procedure to anneal
the SiPM to partially cure an elevated dark rate due to
neutron radiation damage. We could consider this if the
damage is severe.
</p>
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