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<p>Folks,</p>
<p>Find the minutes below and at
<a class="moz-txt-link-freetext" href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_18,_2016#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_October_18,_2016#Minutes</a>
.</p>
<p> -- Mark</p>
<p>__________</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, October 18, 2016, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Paul Eugenio, Sasha Ostrovidov</li>
<li> <b>JLab</b>: Thomas Britton, Brad Cannon, Eugene
Chudakov, Mark Ito (chair), Simon Taylor, Beni
Zihlmann</li>
</ul>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<p>The schedule still had beam for Hall D starting on
November 9.
</p>
<h3><span class="mw-headline" id="HV_Scan_Planning">HV
Scan Planning</span></h3>
<ul>
<li> Beni pointed out that doing the HV scan is
essentially a gain balancing exercise.</li>
<li> Brad reported that we are ready to execute program,
as far as the software is concerned.</li>
<li> Sasha asked about the criteria for setting the
voltages. Beni would like to shoot for a 35 mV MIP
amplitude when the hit is from the far end of the
counter and a 10 mV discriminator threshold. We will
have to try these settings to see if they yield
acceptable rate and efficiency.</li>
<li> Beni asked Sasha if he could do a timing test with
his test set-up, triggering in the middle of the
counter (with the trigger counters) and looking at the
mean time difference distribution when the high
voltage is set to obtain a 50 mV amplitude for MIP
particles. Sasha will give it a try.</li>
</ul>
<h3><span class="mw-headline"
id="PMT_bases_with_Amplifiers">PMT bases with
Amplifiers</span></h3>
<p>On Thursday of last week, we met with Vladimir Popov of
RadCon. He designed the bases for the tagger hodoscope
which have an on-board amplifier. Present were Brad,
Paul, Beni, Eugene, and Mark. We discussed several
issues and design decisions that need to be made.
</p>
<ul>
<li> Should we continue to use a passive splitter to
create ADC and discriminator signal paths or should we
run a second signal cable from the PMT base?</li>
<li> Should we add an inductor or transformer to the
output stage to remove a baseline shift due to the
intrinsic AC coupling of the amplifier?</li>
<li> Should we design a new circuit board or modify the
existing voltage divider circuit, perhaps adding a
daughter board?</li>
<li> What is the schedule for the upgrade?</li>
<li> How many of the PMT bases do we want to replace?
All of them? Some of them? Which ones?</li>
</ul>
<p>We will have to put together a specification that
answers these questions and gives requirements for gain
(i. e., current reduction), power limits (i. e., HV
supply current maximum), and bandwidth (i. e., rise
time). There are also administrative questions to be
answered before work can start.
</p>
<h3><span class="mw-headline" id="Status_in_the_Hall">Status
in the Hall</span></h3>
<ul>
<li> The "TOF1" crate had been disassembled to serve as
a test bed for an FADC250 pedestal setting problem.
ADC read-out is unavailable until further notice. Hot
Check-Out is therefore impossible right now.</li>
<li> The integral non-linearity (INL) calibration is
underway. Beni sent sample data to Bryan Moffit and Ed
Jastrzembski but has not heard back from them about
the format.</li>
<li> Beni found the TOF HV would not come on. The power
had been disconnect, probably when the HV power supply
for the Compton Calorimeter was being installed.</li>
</ul>
<h3><span class="mw-headline"
id="Re-Segmentation_of_the_TOF">Re-Segmentation of the
TOF</span></h3>
<p>Paul presented an idea he has been thinking about for
reducing TOF rates by changing the geometry of the inner
counters. See <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/talks/2016/TOF-Mods.pdf">his
slides</a> for sketches of the idea. In summary the
beam hole is enlarged from a 12 by 12 cm square to 18 by
18 cm. Also the current half-length paddles are split
into two half-length and half-width paddles. The
enlarged beam hole itself lowers the rate and the
increased segmentation helps the cause. Paul also showed
a plot of momentum vs. polar angle for charged particles
with TOF matches indicating the angular regions
subtended by both sizes of the beam hole.
</p>
<h3><span class="mw-headline" id="Action_Items">Action
Items</span></h3>
<ol>
<li> Hot Check Out, after TOF1 put back together. (Brad
and Beni)</li>
<li> INL calibration. (Beni)</li>
</ol>
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