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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,_November_29,_2016#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_29,_2016#Minutes</a>
.</p>
<p> -- Mark<br>
</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, November 29, 2016, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Sasha Ostrovidov</li>
<li> <b>JLab</b>: Thomas Britton, Brad Cannon, Eugene
Chudakov, Mark Ito (chair), Simon Taylor, Beni
Zihlmann</li>
</ul>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_previous_meeting">Review
of minutes from the previous meeting</span></h3>
<p>We reviewed the [[GlueX TOF Meeting, November 15,
2016#Minutes|minutes of the November 15 meeting.
</p>
<ul>
<li> The four ADC channels that were dead actually had a
problem with the DAC that sets the baseline. These
channels seem to have a bit missing (or stuck) such
that the baseline finding algorithm gets confused. The
apparent lack of hits was due to a wildly mis-set
baseline value. Beni figured this out and set the
baseline values by hand.</li>
<li> Beni tried to reverse the INL correction of the
Spring data but realized that the function that makes
the correction is not invertible. He has abandoned
that effort. He did notice that some of the channels
have INL profiles quite different from what he has
seen before.</li>
<li> Beni reports that the HV scan software is working
with ROOT 6 now.</li>
<li> Sasha reports that he fixed the Lecroy 1440
mainframe at FSU. He will not need a replacement from
JLab.</li>
<li> We will likely send the new PMTs to FSU for
testing. The property and shipping procedure is not
onerous.</li>
</ul>
<h3><span class="mw-headline"
id="PMT_bases_with_Amplifiers">PMT bases with
Amplifiers</span></h3>
<ul>
<li> Beni is collecting information to pass on to
Vladimir Popov for his design.</li>
<li> We need to make a decision about whether to re-use
the voltage divider chain on in the bases, introducing
the possibility of a mezzanine board, or re-adjust the
voltages to optimize for lower HV operation. Beni will
think about doing a test with the laser to measure the
degradation in time resolution with lower voltage.</li>
</ul>
<h3><span class="mw-headline" id="Efficiency_Study">Efficiency
Study</span></h3>
<p>Beni went through <a
href="https://halldweb.jlab.org/wiki/index.php/TOF_Efficiencies"
title="TOF Efficiencies"> his wiki page</a> describing
a study of TOF efficiency using charged particles. See
his page for details and plots.
</p>
<ul>
<li> Beni concludes that using tracking to measure
efficiency is tricky.</li>
<li> The effect if high rates is two-fold: it causes
more accidentals, artificially increasing efficiency,
and can reduce the gain of tube, causing a real loss
of efficiency due to low pulse amplitude.</li>
<li> There is a marked dependence of the method on the
momentum of the charged tracks. At 3 GeV/c, efficiency
is measured to be acceptably high in the bulk of the
TOF.</li>
<li> At the extreme edges of the array there is a marked
reduction of efficiency. Simon thought that this is
likely due to tracks which are projected to the TOF
but actually encounter the BCAL on the way. Beni will
investigate.</li>
</ul>
<h3><span class="mw-headline"
id="TOF_Time_Resolution_for_Charged_Tracks">TOF Time
Resolution for Charged Tracks</span></h3>
<p>Brad presented <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/talks/2016/TOF%20PMT%20Study.pdf">slides
describing his study</a>. He looked at the resolution
of the difference between the corrected TOF time
(corrected for charged track propagation time) and the
RF time. He sees significant degradation of resolution
as the number of TOF hits used to construct a TOF point
is reduced. See his slides for details.
</p>
<h3><span class="mw-headline" id="Cosmics_test_at_FSU">Cosmics
test at FSU</span></h3>
<p>Sasha went through <a rel="nofollow" class="external
text"
href="http://hadron.physics.fsu.edu/%7Eostrov/tof/20161129/">his
wiki page</a> describing a recent timing measurement
he did with his test set-up using 1200 V and 1500 V on
the PMTs. The at 1500 V he sees 161 ps and that degrades
to 187 ps at 1200 V, a 16% increase. No walk corrections
were applied; these may have a significant effect on the
comparison. He also showed a similar, though not
identical, measurement from 2009 that gave 124 ps for
the same quantity. He plans to repeats this measurement
using a constant-fraction discriminator.
</p>
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