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Folks,<br>
<br>
Find the minutes below and at<br>
<br>
<a class="moz-txt-link-freetext" href="https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_23,_2014#Minutes">https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_23,_2014#Minutes</a><br>
<br>
-- Mark<br>
_____________________________________________<br>
<br>
<h1 id="firstHeading" class="firstHeading">GlueX TOF Meeting,
September 23, 2014<span class="mw-headline" id="Minutes"> Minutes</span>
</h1>
<div id="bodyContent">
<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Hussein Al Ghoul, Sasha Ostrovidov, Aristeidis
Tsaris
</li>
<li> <b>JLab</b>: Mark Ito, Beni Zihlmann
</li>
</ul>
<h2> <span class="mw-headline" id="Review_of_Previous_Meetings">Review
of Previous Meetings</span></h2>
<p>We went over minutes from <a
href="https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_2,_2014"
title="GlueX TOF Meeting, September 2, 2014">September 2</a>
and from <a
href="https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_9,_2014"
title="GlueX TOF Meeting, September 9, 2014">September 9</a>.
</p>
<ul>
<li> Sasha reports that TDC inefficiency is still and issue.
There is a factor of
</li>
</ul>
<p>two in the occupancy among certain channels.
</p>
<ul>
<li> Aristeidis continues work on the event display. He is now
working on the TOF library, adjusting constants in the code,
for example the time window for matching FADC and TDC hits.
For the viewer, he needs a bit more information that that
provided the TOF point object and is looking at how to get it.
</li>
<li> FSU has been monitoring the rates in the TOF continuously.
The high voltage has been on for about a month and a half now.
There were two noisy channels at the beginning, but they have
quieted down for unknown reasons.
</li>
</ul>
<h2> <span class="mw-headline" id="Collaboration_Meeting">Collaboration
Meeting</span></h2>
<p>Aristeidis will give the presentation at the meeting. Sasha and
Hussein will also make the trip.
</p>
<h2> <span class="mw-headline" id="Hot_Check-Out">Hot Check-Out</span></h2>
<p>We reviewed the <a
href="https://accweb.acc.jlab.org/hco/checklists?groupId=55"
class="external text" rel="nofollow">list</a> for the TOF. No
comments were offered.
</p>
<h2> <span class="mw-headline" id="Shift-Takers.27_Instructions">Shift-Takers'
Instructions</span></h2>
<p>We reviewed the <a
href="https://hdops.jlab.org/wiki/index.php/Time-of-Flight_System_Shift"
class="external text" rel="nofollow">instructions</a>, which
are still pretty basic. Sasha commented that we still need
instructions on how to write the online monitoring code.
</p>
<h2> <span class="mw-headline" id="Commissioning_Plan">Commissioning
Plan</span></h2>
<p>We looked at the <a
href="https://hdops.jlab.org/wiki/index.php/Time-of-Flight_System_Commissioning"
class="external text" rel="nofollow">commissioning plan</a>
for the TOF that Sasha put together last month. It is rather
complete. No comments were offered.
</p>
<h2> <span class="mw-headline" id="Calibration">Calibration</span></h2>
<p>Sasha took another 2 million events a couple of weeks ago and
transferred them to FSU. Data taking was at one point
interrupted by the power outage in the Hall. Good data came from
6-8 hours of running and came to 150 GB. Using this data he has
been developing the calibration procedure further.
</p>
<p><b>First Step</b>: Looking at each plane separately he fits
straight lines to hit counters, getting the hit position with
end-to-end time differences. He uses these fits to adjust the
end-to-end timing offset and the speed of light in the counter
and iterates.
</p>
<p><b>Second Step</b>: Here he obtains module-to-module mean time
offsets. He has tried two approaches.
</p>
<ol>
<li> Events with two counters in each plane. A line is fit to
the trajectory, mean time offsets are obtained and the process
iterated. For some counters he sees participation in very few
such tracks (as low as 100).
</li>
<li> Events with one counter in each plane. This gives mean time
offsets from counters in different planes by definition, but
given all such pairs time offsets can be calculated for all
counters in all planes. Here he is running into the ambiguity
between cosmics which go back-to-front and those going
front-to-back. This is introducing an ambiguity of about 100
ps.
</li>
</ol>
<p>Sasha thinks that with beam, a lot of these problems will
disappear; calibration will be relatively easy with particles
from a target.
</p>
</div>
<br>
<pre class="moz-signature" cols="72">--
Mark M. Ito, Jefferson Lab, <a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295</pre>
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