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Folks,<br>
<br>
Find the minutes below and at <a class="moz-txt-link-freetext" href="https://goo.gl/Y6Byc5">https://goo.gl/Y6Byc5</a> .<br>
<br>
-- Mark<br>
_______________________________<br>
<br>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, July 5, 2016, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
<div id="bodyContent" class="mw-body-content">
<div id="mw-content-text" dir="ltr" class="mw-content-ltr"
lang="en">
<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Brad Cannon, Sasha Ostrovidov</li>
<li> <b>JLab</b>: Mark Ito (chair), Simon Taylor, Beni
Zihlmann</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/9WMX/">recording of this
meeting</a> on the BlueJeans site.
</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 skimmed the <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_28,_2016#Minutes"
title="GlueX TOF Meeting, June 28, 2016">minutes from
June 28</a>.
</p>
<ul>
<li> Turns out we purchased 194 PMTs altogether, but 4
of them were for Elton to use (on a non-TOF project).
Thus the 190 for the TOF use is correct. One tube was
broken at the FSU machine shop. 3 spares were found by
Beni in the cabinet in the hall, 10 are in the
mini-TOF at FSU. 176 are part of the TOF. It all adds
up.</li>
<li> Mark has a call into Ardavan Ghassemi at Hamamatsu
asking for quotes on 10-stage and 8-stage tubes.</li>
<li> Sasha found an 8-stage tube at FSU. Paul Eugenio
claims (via email) than an 8-stage tube was sent to
Elton at some point.</li>
</ul>
<h3><span class="mw-headline" id="PMT_Gain_Loss">PMT Gain
Loss</span></h3>
<h4><span class="mw-headline" id="Gain_Studies">Gain
Studies</span></h4>
<p>Beni described his write-up (previously this section
was in the agenda section of this page).
</p>
<ol>
<li> The following plots show the signal peak amplitude
for hits that are matched to tracks<br>
the data are from different runs where we did a beam
current scan starting with 40nA and going up to 150nA.
At 40nA beam current the peak amplitudes look still
reasonable, but already at 80nA a degradation is
noticeable which becomes critical at even higher
currents(luminosities). The radiator was 50um diamond.
These data were taken near the end of the run. There
is no correction for position/attenuation.
<ul>
<li> Run 11634 with 40nA beam current:<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run11634.gif"
class="image"><img alt="Adc peak run11634.gif"
src="cid:part3.07080101.06060404@jlab.org"
srcset="/wiki/images/thumb/a/ae/Adc_peak_run11634.gif/450px-Adc_peak_run11634.gif
1.5x,
/wiki/images/thumb/a/ae/Adc_peak_run11634.gif/600px-Adc_peak_run11634.gif
2x" height="155" width="300"></a></li>
<li> Run 11635 with 80nA beam current:<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run11635.gif"
class="image"><img alt="Adc peak run11635.gif"
src="cid:part5.03090509.03010402@jlab.org"
srcset="/wiki/images/thumb/a/a9/Adc_peak_run11635.gif/450px-Adc_peak_run11635.gif
1.5x,
/wiki/images/thumb/a/a9/Adc_peak_run11635.gif/600px-Adc_peak_run11635.gif
2x" height="163" width="300"></a></li>
<li> Run 11637 with 110nA beam current:<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run11637.gif"
class="image"><img alt="Adc peak run11637.gif"
src="cid:part7.03070309.02060300@jlab.org"
srcset="/wiki/images/thumb/1/1a/Adc_peak_run11637.gif/450px-Adc_peak_run11637.gif
1.5x,
/wiki/images/thumb/1/1a/Adc_peak_run11637.gif/600px-Adc_peak_run11637.gif
2x" height="164" width="300"></a></li>
<li> Run 11636 with 150nA beam current:<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run11636.gif"
class="image"><img alt="Adc peak run11636.gif"
src="cid:part9.02090004.07000903@jlab.org"
srcset="/wiki/images/thumb/f/f6/Adc_peak_run11636.gif/450px-Adc_peak_run11636.gif
1.5x,
/wiki/images/thumb/f/f6/Adc_peak_run11636.gif/600px-Adc_peak_run11636.gif
2x" height="158" width="300"></a></li>
</ul>
</li>
<li> The degradation of the PMTs over the spring run
period is illustrated with the following plots showing
the RAW ADC Signal amplitudes for an early run (run
10346) and a late run (run 11634 same as above low
current 40nA)
<ul>
<li>Raw TOF data Signal amplitude RUN 10346 (left)
track matching hits (right):<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofpmt_amp_raw_run10346.gif"
class="image"><img alt="Tofpmt amp raw
run10346.gif"
src="cid:part11.08070505.01080907@jlab.org"
srcset="/wiki/images/thumb/c/ce/Tofpmt_amp_raw_run10346.gif/450px-Tofpmt_amp_raw_run10346.gif
1.5x,
/wiki/images/thumb/c/ce/Tofpmt_amp_raw_run10346.gif/600px-Tofpmt_amp_raw_run10346.gif
2x" height="169" width="300"></a> <a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run10346.gif"
class="image"><img alt="Adc peak run10346.gif"
src="cid:part13.06000001.03040907@jlab.org"
srcset="/wiki/images/thumb/9/97/Adc_peak_run10346.gif/450px-Adc_peak_run10346.gif
1.5x,
/wiki/images/thumb/9/97/Adc_peak_run10346.gif/600px-Adc_peak_run10346.gif
2x" height="154" width="300"></a></li>
<li>Raw TOF data Signal amplitude RUN 11634 (left)
track matching hits (right)::<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofpmt_amp_raw_run11634.gif"
class="image"><img alt="Tofpmt amp raw
run11634.gif"
src="cid:part15.01090502.07010608@jlab.org"
srcset="/wiki/images/thumb/1/1c/Tofpmt_amp_raw_run11634.gif/450px-Tofpmt_amp_raw_run11634.gif
1.5x,
/wiki/images/thumb/1/1c/Tofpmt_amp_raw_run11634.gif/600px-Tofpmt_amp_raw_run11634.gif
2x" height="187" width="300"></a> <a
href="https://halldweb.jlab.org/wiki/index.php/File:Adc_peak_run11634.gif"
class="image"><img alt="Adc peak run11634.gif"
src="cid:part3.07080101.06060404@jlab.org"
srcset="/wiki/images/thumb/a/ae/Adc_peak_run11634.gif/450px-Adc_peak_run11634.gif
1.5x,
/wiki/images/thumb/a/ae/Adc_peak_run11634.gif/600px-Adc_peak_run11634.gif
2x" height="155" width="300"></a></li>
</ul>
</li>
</ol>
<p>So there is both a severe rate dependence and long-term
degradation of the gain. Sasha noted that the beginnings
of this effect was visible in the Spring 2015 data.
</p>
<h4><span class="mw-headline" id="Current_PMT_HV">Current
PMT HV</span></h4>
<p>Sasha put together a histogram of the current HV
settings:<br>
<a
href="https://halldweb.jlab.org/wiki/index.php/File:Current_HV_settings.png"
class="image"><img alt="Current HV settings.png"
src="cid:part19.04060400.02030201@jlab.org"
srcset="/wiki/images/thumb/d/d1/Current_HV_settings.png/450px-Current_HV_settings.png
1.5x,
/wiki/images/thumb/d/d1/Current_HV_settings.png/600px-Current_HV_settings.png
2x" height="241" width="300"></a>
</p>
<h3><span class="mw-headline" id="Discussion">Discussion</span></h3>
<ul>
<li> Beni has been looking at signals in the Hall. He
sees many large (2 V) pulses. He will continue to
explore reasonable running parameters.</li>
<li> Beni talked to Tom about the mechanical procedure
for replacing tubes. We would need to build a jig hold
the PMT to the light guide during gluing. He sketch an
idea with springs to hold the PMT to a clamp around
the light guide.</li>
<li> The nominal scheme Beni would like to try is:
<ol>
<li> Reduce the HV to get a gain reduction of about
a factor of four.</li>
<li> Reduce the discriminator threshold to 15 mV
from 50 mV.</li>
<li> Reduce the ADC range maximum from 2 V to 0.5 V
(this can be done by changing a jumper on the
boards).</li>
</ol>
</li>
<li> Sasha will look into reviving his test set-up at
FSU. He could then look at efficiency and timing with
lower voltages and thresholds.</li>
<li> We wondered if we could do similar tests with the
TOF in the Hall with cosmics. No easy ideas presented
themselves.</li>
<li> Beni pointed out the <a
href="https://halldweb.jlab.org/wiki/index.php/Photomultiplier_Plateaus"
title="Photomultiplier Plateaus">plateau curves on
the TOF wiki pages</a>. Turns out that these were
done at IU a long time ago and the tubes are not
clearly identified making them hard to interpret.</li>
<li> Sasha did some plateau curves on 10-stage and
8-stage tubes at one point. He presented them at a
collaboration meeting. He will try to dig up the talk.</li>
<li> We decided to try plateau-ing the counters in the
Hall using the discriminator scalers. Even with
cosmics, this should be possible. It could even be
automated, potentially.</li>
<li> Beni has got the laser box now. He will set-up a
rate test.</li>
</ul>
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<li id="lastmod"> This page was last modified on 5 July 2016,
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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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