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Folks,<br>
<br>
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_3,_2015">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_3,_2015</a>
.<br>
<br>
-- Mark<br>
_______________________________________________________________<br>
<br>
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<h1 id="firstHeading" class="firstHeading" style="font-weight:
bold;" lang="en"><span dir="auto">GlueX TOF Meeting, November
3, 2015</span>, Minutes</h1>
<div id="bodyContent" class="mw-body-content"><span
class="mw-headline" id="Minutes"></span>
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lang="en">
<p style="widows: 3; orphans: 3; margin: 1em 0px;
line-height: 1.2em;">Present:</p>
<ul style="list-style-type: square;">
<li><b>FSU</b>: Hussein Al Ghoul, Brad Cannon, Sasha
Ostrovidov, Aristeidis Tsaris</li>
<li><b>JLab</b>: Mark Ito (chair), Simon Taylor</li>
</ul>
<h3 style="page-break-after: avoid; font-weight: bold;"><span
class="mw-headline" id="Calibration_with_Cosmics">Calibration
with Cosmics</span></h3>
<p style="widows: 3; orphans: 3; margin: 1em 0px;
line-height: 1.2em;">Sasha gave a report on recent work.</p>
<ul style="list-style-type: square;">
<li>He has succeeded in taking cosmic data, but had a
couple of difficulties:
<ol>
<li>He needed to attempt to start runs several times
before getting any triggers at all. He suspects that
with multi-block readout of the CAEN TDCs, the token
passing between modules would stop, hanging the
system.</li>
<li>ROCTOF1, which houses the FADCs, would crash in
minutes from the start of the run. A hard reboot was
needed to get things going again.
<ul style="list-style-type: square;">
<li>This problem has resolved itself recently.</li>
</ul>
</li>
</ol>
<ul style="list-style-type: square;">
<li>In the end he got a few times 100 k events.</li>
</ul>
</li>
<li>The trend of higher gains at the edges of the arrays
seen in beam data is also seen in cosmic data.
<ul style="list-style-type: square;">
<li>This rules out the magnetic field, or a systematic
problem using beam tracks.</li>
<li>Possible culprits:
<ul style="list-style-type: square;">
<li>Different HV supplies than those used at FSU.</li>
<li>Different HV cables.</li>
</ul>
</li>
<li>He is working on a program to adjust HV to
equalize gains. Data will be taken, gains measured,
HV adjusted, and process iterated.</li>
<li>He is also seeing a difference in the gain when
comparing a hit in the middle of the paddle versus
one near the ends, even after accounting for
attenuation. The gain is about 10% higher near the
ends.</li>
</ul>
</li>
<li>He is trying to judge the effect of gain calibration
using a set of "tracks" in the TOF in cosmic data. He
requires 5 counters minimum. The yield of such events is
extremely low, about one part in ten thousand.
<ul style="list-style-type: square;">
<li>The trigger rate is about 600 Hz.</li>
<li>The threshold for a single FADC channel to be read
out is 500 counts. The trigger threshold on the sum
is about 50,000 typically, but other values have
been tried.</li>
</ul>
</li>
</ul>
<h3 style="page-break-after: avoid; font-weight: bold;"><span
class="mw-headline" id="Calibration">Calibration</span></h3>
<ul style="list-style-type: square;">
<li>Brad is in contact with Sean Dobbs about a plug-in to
be used in the calibration challenge.</li>
<li>He is also cleaning up the script to drive the
calibrations already done.</li>
</ul>
</div>
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