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<p>Friend,</p>
<p>Please find the minutes <a moz-do-not-send="true" href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_August_11,_2021#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 TOF Meeting, August 11, 2021, </span><span class="mw-headline" id="Minutes">Minutes</span></h2>
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<p>Present: Edmundo Barriga, Eugene Chudakov, Mark Ito
(chair), Sasha Ostrovidov, Susan Schadmand, Beni
Zihlmann
</p>
<p>There is a <a rel="nofollow" class="external text" href="https://bluejeans.com/s/p94Csgi@3CM/">recording
of this meeting</a>. Log into the <a rel="nofollow" class="external text" href="https://jlab.bluejeans.com">BlueJeans site</a>
first to gain access (use your JLab credentials).
</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_TOF_Meeting,_June_30,_2021#Minutes" title="GlueX TOF Meeting, June 30, 2021">minutes of
the meeting on June 30</a>. Paul and Edmundo brought
some PMTs from FSU. In the process of marking PMTs as
returned on the loan agreement (JLab to FSU) we ran into
a complication in the accounting that will not be
described here. Negotiations are in progress.
</p>
<h3><span class="mw-headline" id="PMT_Replacement">PMT
Replacement</span></h3>
<p>Edmundo reported on the repair trip he and Paul Eugenio
made to JLab, July 12-16. Four tubes were replaced. The
only difficulty encountered was that the "PMT clipper"
used to break the joint between PMT and light guide was
designed for TOF I and had to have some field mods to
work with some of the TOF II tubes. Other that that, the
operation went smoothly.
</p>
<p>After the work was done Beni turned on all of the HV
and saw scalars counting for all of the channels save
one. He later found a cable not bayoneted into the
splitter; re-seating it fixed the channel.
</p>
<h3><span class="mw-headline" id="Plans_for_HV_Scan">Plans
for HV Scan</span></h3>
<p>Beni has created the voltage configuration files for an
HV scan. Voltages are uniform across the array in each
file and files have been produced in 25 V increments
from 1175 to 1375 V. The code to analyze the data looks
for minimum ionizing peaks and fits an exponential to
the peak position as a function of voltage. With these
fits we can pick a gain-balanced operating point. The
software needs to be checked to see if it still works
with recent releases.
</p>
<h3><span class="mw-headline" id="Test_of_replaced_PMTs">Test
of replaced PMTs</span></h3>
<p>Sasha has looked at the four PMTs removed from the TOF.
He led us through <a rel="nofollow" class="external
text" href="http://hadron.physics.fsu.edu/~ostrov/tof/20210802/">his
web page summarizing results</a>. He uses a UV LED and
measures the position of the single-photoelectron peak
with the HV set at 1750 V. He can then compare with the
same measurement performed before the PMT was included
in a module assembly years ago. The tubes show a
reduction in gain of about a factor of two. This is
significant, but not a cause for panic, even though
other tubes still in the array may suffer from the same
loss in gain.
</p>
<h3><span class="mw-headline" id="FADC_Replacement">FADC
Replacement</span></h3>
<p>Beni is talking to the electronics guys about getting
four FADC-250s to replace the ones that have a bad bit
in the DAC for certain channels, one channel per board
as it turns out. He is hopeful that the spares will be
found and we can do the replacement before the run.
</p>
<h3><span class="mw-headline" id="Actions_Items">Actions
Items</span></h3>
<ol>
<li> Schedule time for testing the TOF II trigger.</li>
<li> Do the HV scan and analyze the results.</li>
<li> Replace the defective FADCs.</li>
</ol>
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