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<p>Please find the minutes below and at
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, August 9, 2016</span><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>: Eugene Chudakov, Mark Ito (chair),
Simon Taylor, Beni Zihlmann</li>
</ul>
<h3><span class="mw-headline" id="PMT_Order">PMT Order</span></h3>
<p>The order for the initial 25 PMTs has been issued as a
PO. The order for an additional 6 is in the system,
signed, and assigned a buyer.
</p>
<h3><span class="mw-headline"
id="TOF_rates_during_lumi_scan">TOF rates during lumi
scan</span></h3>
<p>Beni looked at runs 11634-11637. He plots TOF rates as
recorded by EPICS (per PMT) vs. electron beam current
from the luminosity scan at the end of the Spring 16 run
for selected paddles. Recall that paddle 1 to 19 are
regular width/length paddles, paddle 20 and 21 are
narrow width long paddles and paddle 22 is a short
single ended paddle.
</p>
<p>The rates are in Hz as a function of beam current in
nA. The data are from runs 11634 to 11637 where
luminosity scans were done from 40 to 140nA. The
collimator was set to 5mm diameter and the radiator is
3x10-4 with LH target full.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:TOF_PMT_rates.gif"
class="image"><img alt="TOF PMT rates.gif"
src="cid:part1.608C53A2.24F98EBD@jlab.org"
height="774" width="996"></a>
</p>
<p>Beni noted that if the intensity goes up by a factor of
five, the highest rate counters will be unusable.
Mitigations: shielding? higher magnetic field?
</p>
<h3><span class="mw-headline" id="Cosmic_data">Cosmic data</span></h3>
<p>Beni showed histograms of the mean time difference
between paddle 21 of both planes, both for recent cosmic
data at various voltages and for a run during this past
Spring with the photon beam.
</p>
<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofres_1200V.gif"
class="image"><img alt=""
src="cid:part3.C441BD8F.67A8DFA3@jlab.org"
class="thumbimage"
srcset="/wiki/images/thumb/a/ae/Tofres_1200V.gif/450px-Tofres_1200V.gif
1.5x, /wiki/images/a/ae/Tofres_1200V.gif 2x"
height="181" width="300"></a>
<div class="thumbcaption">1200V</div>
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<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofres_1250V.gif"
class="image"><img alt=""
src="cid:part5.D14CCBD4.59823F62@jlab.org"
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srcset="/wiki/images/thumb/5/5a/Tofres_1250V.gif/450px-Tofres_1250V.gif
1.5x, /wiki/images/5/5a/Tofres_1250V.gif 2x"
height="181" width="300"></a>
<div class="thumbcaption">1250V</div>
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<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofres_1500V.gif"
class="image"><img alt=""
src="cid:part7.F0C90669.6D33A4EF@jlab.org"
class="thumbimage"
srcset="/wiki/images/thumb/0/04/Tofres_1500V.gif/450px-Tofres_1500V.gif
1.5x, /wiki/images/0/04/Tofres_1500V.gif 2x"
height="181" width="300"></a>
<div class="thumbcaption">1500V</div>
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<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Tofres_run11666.gif"
class="image"><img alt=""
src="cid:part9.EB186296.B79FBD54@jlab.org"
class="thumbimage"
srcset="/wiki/images/thumb/8/8e/Tofres_run11666.gif/450px-Tofres_run11666.gif
1.5x, /wiki/images/8/8e/Tofres_run11666.gif 2x"
height="181" width="300"></a>
<div class="thumbcaption">Spring '16, run 11666</div>
</div>
</div>
<p>There is not a marked difference in resolution between
the various voltage settings for the cosmic data.
However, all settings show poorer resolution and than
the beam data. Clearly, the beam data has much better
conditions for timing resolution measurements. If there
is a trend in the cosmic data with voltage setting, it
might be masked by the effect of the cosmic conditions.
</p>
<p>Sasha suggested a position cut (time-difference cut) to
ensure that the cosmic hits are coming from the
"intersection" region defined by the crossed counters.
This might clean things up for the cosmics. Beni will
try that.
</p>
<p>Beni also noted that although the gain on the inner
counters has been reduced, he does not see any dead
counters in the cosmic runs.
</p>
<h3><span class="mw-headline" id="Next_Meeting">Next
Meeting</span></h3>
<p>We will meet again in a week.
</p>
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