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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_TOF_Meeting,_June_5,_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 TOF Meeting, June 5, 2019</span></h2>
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<p>Present:
</p>
<ul>
<li> <b> FSU: </b> Paul Eugenio</li>
<li> <b> JLab: </b> Thomas Britton, Mark Ito (chair),
Simon Taylor</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/Pspno/">recording of
this meeting</a> on the BlueJeans site. Use your JLab
credentials to access it.
</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 <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_May_22,_2019#Minutes"
title="GlueX TOF Meeting, May 22, 2019">the minutes
from the meeting on May 22</a>.
</p>
<ul>
<li> Mark submitted the order for the last of the
acrylic light guide material.</li>
<li> Mark has ordered RTV and primer for Paul.</li>
<li> The Hamamatsu PMT model we used in the original
construction has been discontinued. Paul and Mark
reviewed the suggested replacement model and it looks
like it should work. The physical dimensions and
performance specs are the same as the original.</li>
<li> The design of the racks for storage in the Hall has
been settled.</li>
<li> Paul would like Mark to remind Tim to send the
final drawings for the shield collars so FSU can get
started on them.</li>
<li> After reading the minutes Sean Dobbs told us that
he thinks that the software issues we discussed may
not be so bad. He thinks he has structured things so
that the changes will be relatively painless.</li>
<li> Thomas will talk to David Lawrence about monitoring
histograms for the new TOF configuration.</li>
</ul>
<h3><span class="mw-headline" id="Construction_Update">Construction
Update</span></h3>
<p>Paul gave the report.
</p>
<ul>
<li> The scintillator bars from Eljen were unboxed and
given a physical inspection. Dimensions were checked
and surface quality assessed. They look good, save for
a few very minor nicks here and there.</li>
<li> Scintillator attenuation length measurements:
<ul>
<li> The bars arrived wrapped in transparent plastic
sheets.</li>
<li> Attenuation length measurements were performed
on the wrapped and unwrapped bars by moving a UV
LED along the surface. Sasha Ostrovidov posted <a
rel="nofollow" class="external text"
href="http://hadron.physics.fsu.edu/~ostrov/tof/20190605/">some
representative ADC data</a> from the
measurements. The unwrapped measurements look as
good as those obtained during the original
construction.</li>
<li> The measurements for the wrapped bars are a
factor of two worse than unwrapped (the wrapping
is in optical contact with the scintillator
surface) and the factor seems consistent from bar
to bar. The idea is to do the measurement with the
wrapping on all of the bars, and only do spot
checks without the wrapping. This is greatly
reduce the amount of handling the bars experience,
while still catching any bars with very poor
attenuation length.</li>
</ul>
</li>
<li> Light guides
<ul>
<li> We are expecting the final order of acrylic to
come in this week.</li>
<li> The final cutting of ends for the made light
guides has been done.</li>
<li> Polishing has started.</li>
</ul>
</li>
<li> First-article module
<ul>
<li> Paul plans to take the first pair of polished
light guides and assemble a complete module.</li>
<li> Some of the procedures have changed since the
original construction.</li>
<li> After assembly, the module will go to testing.</li>
<li> By going through the complete procedure, Paul
hopes to iron out any glitches in the construction
procedure.</li>
<li> The complete module should be done by the next
meeting.</li>
</ul>
</li>
<li> Paul may want JLab to purchase some extruded
aluminum bars to construct fixtures including one for
carrying the modules around the building safely. </li>
<li> The acrylic bars for the light guides were all
manufactured by the same company as we used last time,
although the purchase went through two different
suppliers. There are no UV inhibitors in the acrylic.
In the end, there was no need to identify a different
manufacturer. Paul plans to measure transmission all
of the light guides with an UV source and a
photo-spectrometer.</li>
</ul>
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