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<p>Folks,</p>
<p>Please find the minutes below and at
<a class="moz-txt-link-freetext" href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_10,_2017">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_10,_2017</a>
.</p>
<p> -- Mark<br>
</p>
______________<br>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, January 10, 2017, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Paul Eugenio</li>
<li> <b>JLab</b>: Thomas Britton, Brad Cannon, Mark Ito
(chair)</li>
</ul>
<h3><span class="mw-headline" id="Lucite_Shield_Results">Lucite
Shield Results</span></h3>
<p>Paul led us through <a rel="nofollow" class="external
text" href="https://logbooks.jlab.org/entry/3448871">his
logbook entry</a> (shown below) tabulating the results
of the test of a Lucite shield for the counters closest
to the beamline. Data were taken at the end of the Fall
run. Substantial rate reduction was observed with the
TOF discriminator scalers. For example, the 2.25 inches
of Lucite (17% of a radiation length) reduced the rate
in S:21 by about 35% and that in S:22 by about 45%,
independent of the beam rate used in the measurement.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:TOF-Shield-Study-Fall2016-4.png"
class="image"><img
alt="TOF-Shield-Study-Fall2016-4.png"
src="cid:part2.DD6B03DC.8FE736A4@jlab.org"
srcset="/wiki/images/d/d6/TOF-Shield-Study-Fall2016-4.png
1.5x,
/wiki/images/d/d6/TOF-Shield-Study-Fall2016-4.png
2x" height="600" width="800"></a>
</p>
<p>We concluded that the Lucite would not do harm to the
TOF measurement and gives a substantial rate reduction,
reducing the current load on the last dynode of the
PMTs. The hypothesis is that low energy electrons and
positrons are getting ranged out in the additional
shielding. Now that a significant effect has been
observed, the next step is to see what a Monte Carlo
study says. Pending results of that study, the proposal
is to leave the configuration of shielding used in the
study in place for the next run. It appears to be doing
more good than harm.
</p>
<h3><span class="mw-headline" id="PMT_Testing">PMT Testing</span></h3>
<p>Paul drove the 25 PMTs to be tested down to FSU. Five
were retained at JLab for studies. Ashley Ernst, an FSU
grad student, will execute <a rel="nofollow"
class="external text"
href="http://hadron.physics.fsu.edu/wiki/index.php/Photomultiplier_tubes">the
testing procedure</a>.
</p>
<h3><span class="mw-headline"
id="PMT_Voltage_Scan_Analysis">PMT Voltage Scan
Analysis</span></h3>
<p>Brad has been hampered in his efforts by the Lustre
disk problems at JLab. This remains work in progress.
</p>
<h3><span class="mw-headline" id="Collaboration_Meeting">Collaboration
Meeting</span></h3>
<p>Brad will give the TOF report at the upcoming meeting.
</p>
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<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295
</pre>
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