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<p>Flight Timers,</p>
<p>Find the minutes below and at
<a class="moz-txt-link-freetext" href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_24,_2017#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_24,_2017#Minutes</a>
.<br>
</p>
-- Mark<br>
_________________________<br>
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<h2><span class="mw-headline" id="Minutes">Minutes</span></h2>
<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Sasha Ostrovidov</li>
<li> <b>JLab</b>: Thomas Britton, Brad Cannon, Mark Ito
(chair), Simon Taylor, Beni Zihlmann</li>
<li> <b>NU</b>: Sean Dobbs</li>
</ul>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<ul>
<li> The Hall closes on Friday.</li>
<li> Beam due in Hall on Monday during the day.</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 looked over <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_10,_2017#Minutes"
title="GlueX TOF Meeting, January 10, 2017">the minutes
from January 10</a>. No significant comments were made.
</p>
<h3><span class="mw-headline" id="Run_Readiness">Run
Readiness</span></h3>
<ul>
<li> <b>FADC Replacement</b>. Sascha Somov confirms that
the broken FADC that Beni identified is indeed bad and
Sascha will replace it. After that Beni will ask Sergey
Furletov to do a pedestal setting. And after that Beni
will look for channels that have missing bits on their
DACs and either (a) set the pedestals by hand or (b)
replace the units if spares are available.</li>
<li> <b>Online Monitoring</b>. We need a routine such
that problems like the bad FADC are caught early. Brad
has discussed the issue with David Lawrence; there will
be an on-going display of the critical monitoring
histograms in the counting room. There should also be a
set of standard "good" plots with which to compare. Also
it would be nice if there was some sort of
histogram-viewing activity on the checklist for shift
takers. Thomas volunteered to look into these issues.</li>
<li> <b>Hot Check-Out</b>. Beni, Brad, Thomas will get
together and check things out.</li>
</ul>
<h3><span class="mw-headline" id="HV_scan">HV scan</span></h3>
<p>Brad's HV setting jobs are done as of this morning. There
were some issues getting the latest version of the code
from Beni, but those have been sorted. The HV values agree
with Beni's within a few percent. These are for the
double-ended counters; single-ended HV values are still to
come.
</p>
<p>Sean asked about resolution and efficiency with the lower
voltages has been studied by the group. He showed some
plots from the monitoring plots that show poorer
resolution now (at 1200 V for all counters) than in the
spring, 140 ps vs. 100 ps for pi-, obtained after Beni's
most recent calibrations. Beni will try to confirm these
results.
</p>
<p>Beni repeated a test with a new tube using the laser in
the lab. At 1300 V, he can go to 10 MHz without
degradation of the pulse amplitude. At 1500 V, this is no
longer the case.
</p>
<p>Sean showed other plots showing the rate of TOF hit
matches with charged tracks. There is clearly a drop off
for the half-width counters. Beni things that that is due
to degradation in gain for those tubes because of high
currents last Spring. A channel-by-channel HV setting
should bring those back. Beni also thinks that after this
run, we should replace some of these inner tubes.
</p>
<p>Sean remarked that until recently, with the uploading of
Beni's new constants, the poor TOF timing was holding up
calibration, having effects in several other detectors.
Getting good TOF constants early should be a priority this
time.
</p>
<h3><span class="mw-headline" id="Lucite_Shield_Simulation">Lucite
Shield Simulation</span></h3>
<p>Thomas is working on a simulation of rates in the TOF
with and without the Lucite shielding that was installed
in December. He is almost there. He still needs some
details of the geometry, in particular the dimensions of
the inner sleeve that fits inside the beam hole. If he
sees an effect comparable to that see in data, then we can
study how we might optimize the arrangement.
</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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