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<p>People,</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,_March_21,_2017#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_March_21,_2017#Minutes</a>
.<br>
</p>
-- Mark<br>
___________________________<br>
<br>
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<h2><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, Mark Ito
(chair), Simon Taylor, Beni Zihlmann</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/1kPQJ/">recording of
this meeting</a> on the BlueJeans site. Use your JLab
credentials.
</p>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_previous_meeting">Review
of minutes from the previous meeting</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_February_21,_2017#Minutes"
title="GlueX TOF Meeting, February 21, 2017">the
minutes from February 21</a>.
</p>
<ul>
<li> Thomas reported that the <b>lucite shield
simulation</b> needs to be re-run with a version
after Richard's fix to HDGeant's electromagnetic
background generation. In simulation, the shield was
doing more harm than good whereas we saw a benefit in
the test.</li>
<li> Simon continues to work on improvements in
TOF-charged-track matching.</li>
<li> We noticed that several of the questions about the
on-board amplifiers for the bases that were asked last
time remain unanswered.</li>
</ul>
<h3><span class="mw-headline"
id="PMT_gain_history_during_the_Spring_2017_Run">PMT
gain history during the Spring 2017 Run</span></h3>
<p>Beni looked a histograms generated as part of the
overall calibration effort. The energy spectrum of
pulses show clear minimum ionizing peaks and those can
be fit, separately for individual channels and runs to
give a relative gain history for each PMT in the TOF.
For the plots and more details of the analysis, see <a
href="https://halldweb.jlab.org/wiki/index.php/ADC_Peak_Amplitude_during_the_run_period"
title="ADC Peak Amplitude during the run period"> his
wiki page</a>.
</p>
<p>All channels show a similar trend: (1) a slow gain
reduction over the course of the "100 nA" running of
less than 10%, (2) a step down in gain near the
transition from "100 nA" to "150 nA" running, and (3) a
flattening after that transition. We were not able to
come up with a good explanation for features (2) and
(3). the trends are visible in all PMTs; those close to
the beamline as well as those far away, and in both
layers.
</p>
<p>Sasha thought that perhaps the cause was degradation of
the photocathode of the PMTs, Beni thought that
increased temperature of the tubes at high rate may be a
contributor to halting the decline in the corresponding
period.
</p>
<h3><span class="mw-headline" id="Calibration_Status">Calibration
Status</span></h3>
<p>Beni is in the middle of the task, analyzing the ROOT
trees as they become available from skims Sean Dobbs is
doing on Spring-17 data. It takes about 2 or 3 days to
analyze a single run.
</p>
<h3><span class="mw-headline" id="PMT_base_test_in_Hall">PMT
base test in Hall</span></h3>
<p>Paul Eugenio drove one of the counters from the
mini-TOF up to JLab two weeks ago and it was placed on
tables in the Hall. The run ended before we were able to
get the counter mounted in front of the TOF and take
data with beam. Still Beni managed to look at some
pulses from a modified base, on one end of the counter,
with a prototype amplifier. He sees a slight degradation
in rise time. There were some difficulties getting the
amplifier to work; it has been re-soldered multiple
times in the past several weeks. Finally Vladimir Popov
had to supply a new board. He is currently working on a
new board design specific to our bases.
</p>
<p>The counter remains in the Hall. Tom Carstens has
re-arranged things to keep the counter out of the way of
foot traffic.
</p>
<h3><span class="mw-headline"
id="New_PMT_from-the-factory_specs">New PMT
from-the-factory specs</span></h3>
<p>Sasha has tabulated measured specs of the recent batch
of PMTs we purchased as spares from Hamamatsu. See <a
rel="nofollow" class="external text"
href="http://hadron.physics.fsu.edu/TOF/database/PMT_specification.html">his
table</a> for the numbers (old DocDB credentials). He
notes that these tubes have significantly higher gain
that those from the original PMT order, some by over a
factor of two.
</p>
<p>Testing is about to begin at FSU.
</p>
<p>We did a quick mental tabulation of spare PMT's
</p>
<ul>
<li> New order: 30
<ul>
<li> at FSU: 25</li>
<li> at JLab: 5</li>
</ul>
</li>
<li> Spares in the Hall: 3</li>
<li> mini-TOF: 10
<ul>
<li> on counters mounted on fixture at FSU: 8</li>
<li> on counter in Hall: 2</li>
</ul>
</li>
</ul>
<p>Total: 40
</p>
<h3><span class="mw-headline"
id="PMT_replacement_plan_and_counter_reconfiguration">PMT
replacement plan and counter reconfiguration</span></h3>
<p>We discuss how to approach PMT replacement and/or PMT
base modification (to add on-board amplifiers). Both
operations require removal of the PMT from its
lightguide, therefore if we do one then we should do the
other at the same time. There is probably time to do
that this summer, but we would need to start right away
and so far we have not tested the high-rate performance
of the modified bases under realistic conditions. In
particular, we do not know how well the read-out will
handle the DC baseline shift.
</p>
<p>Beni's study of the gain history (above) tells us that
the PMT are not on the way to near-term failure at the
rates we ran in Spring-17.
</p>
<p>Given all of this, we agreed it might be best to keep
the current PMTs and bases as they are for the Fall-17
and Spring-17 runs. After that we can make the changes
with more information about the amplifier design. And in
fact we may be ready to do a physical re-configuration
of the counters as Paul has proposed in the past. A
final decision will require further discussion.
</p>
<h3><span class="mw-headline" id="NIM_Paper">NIM Paper</span></h3>
<p>In his absence, we decided to impose a deadline for a
first draft of the NIM paper on Paul. After furious
discussion we decided on the May Collaboration meeting
as a reasonable due date (May 15).
</p>
<h3><span class="mw-headline" id="Action_Item_Recap">Action
Item Recap</span></h3>
<ol>
<li> Write a draft of the NIM paper (Paul)</li>
<li> Prepare study of scalar rates as a function of time
for next meeting (Brad)</li>
<li> Re-run Lucite shield simulation (Thomas)</li>
<li> Continue TOF-track matching studies/improvements
(Simon)</li>
<li> Call a meeting with Tim, Eugene, and Paul on the
PMT replacement plan (Mark)</li>
</ol>
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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
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