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Friends,<br>
<br>
Find the minutes from yesterday's meeting below and at<br>
<br>
<a class="moz-txt-link-freetext" href="https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_30,_2015#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_30,_2015#Minutes</a>
.<br>
<br>
-- Mark<br>
_______________________________________________________<br>
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<span dir="auto">GlueX TOF Meeting, June 30, 2015</span><span
class="mw-headline" id="Minutes">, Minutes</span><br>
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Present:
<br>
<ul>
<li> <b>FSU</b>: Hussein Al Ghoul, Paul Eugenio, Sasha
Ostrovidov, Aristeidis Tsaris</li>
<li> <b>JLab</b>: Eugene Chudakov, Mark Ito (chair),
Simon Taylor, Beni Zihlmann</li>
</ul>
<br>
<span class="mw-headline" id="Announcements">Announcements</span><br>
<ul>
<li> Beni announced a new policy for official drawings
at the Lab. Access will be by request only in the
future. Eugene mentioned that there may be an
exemption for specific drawings so that they can be
posted on the web.</li>
<li> Yesterday at the Physics Meeting, Paul Mattione
showed plots of β vs. momentum using the TOF that
showed clearly separated pion, kaon, and proton lines.</li>
</ul>
<br>
<span class="mw-headline" id="Calibration.2C_FSU">Calibration,
FSU</span><br>
<br>
Sasha showed some plots from his work using cable
reflections to obtain time-walk corrections. See <a
rel="nofollow" class="external text"
href="http://hadron.physics.fsu.edu/%7Eostrov/tof/20150630/">his
webpage</a> for details.
<br>
<br>
In the time difference between two pulses in a given
channel in the CAEN TDCs, he sees two peaks, one at 150 ns
separation and on at 190. These two peaks are present for
all channels. The time difference between successive peaks
in the FADC shows a single peak at 190 ns separation. A
plot the FADC two-pulse separation vs that of the TDC
shows that these peaks are spurious, probably due to
reflections, thought the rich structure seen is hard to
understand. Sasha also showed various plots looking for a
dependence on the pulse separation with FADC amplitude. He
had hoped that this dependence could be used as the basis
for time-walk corrections. The lack of a clear dependence
on FADC amplitude makes this look hard to do.
<br>
<br>
<span class="mw-headline" id="Calibration.2C_JLab">Calibration,
JLab</span><br>
<br>
Beni showed results in two areas.
<br>
<br>
<span class="mw-headline" id="Attenuation_Lengths">Attenuation
Lengths</span><br>
<br>
Beni has studied attenuation lengths on a counter by
counter basis. He fits the pulse integral for a single end
in the FADCs in bins of position along the counter as
measured by TDC time difference. The resulting points are
fit to two exponentials. The short attenuation length is
about 76 cm and the long one is around 500 cm. He showed
the distribution of these attenuation lengths separately.
See <a
href="https://halldweb.jlab.org/wiki/index.php/ADC_data#ADC_data:_Attenuation_length"
title="ADC data">his wiki page</a> for details.
<br>
<br>
<span class="mw-headline"
id="FADC_time_differences_vs._TDC_time_differences">FADC
time differences vs. TDC time differences</span><br>
<br>
Beni sees the expected correlation between end-to-end time
difference measured by the TDCs vs. that measured by the
FADC. However the relation has a measurable non-linearity;
he parametrized this as a sine (in the region around 0 a
linear function at lowest order). The reason for the
non-linearity is not understood at present. Again see <a
href="https://halldweb.jlab.org/wiki/index.php/TOF_Timing_TDC_vs_ADC"
title="TOF Timing TDC vs ADC">his wiki page</a> for the
plots.
<br>
<br>
<span class="mw-headline" id="Automating_the_Calibration">Automating
the Calibration</span><br>
<br>
Mark brought up the issue. We still have work to do on
this front. The
current constants are produced with a well-defined
procedure but not
easily automated in its current form.
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