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Collaborators,<br>
<br>
Please find the minutes below and at<br>
<br>
<a class="moz-txt-link-freetext" href="https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_4,_2014#Minutes">https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_November_4,_2014#Minutes</a><br>
<br>
-- Mark<br>
__________________________________________________<br>
<br>
<div id="column-content">
<div id="content">GlueX TOF Meeting, November 4, 2014<span
class="mw-headline" id="Minutes"> Minutes</span><br>
<div id="bodyContent">
<br>
Present:
<br>
<ul>
<li> <b>FSU</b>: Hussein Al Ghoul, Paul Eugenio, Sasha
Ostrovidov, Aristeidis Tsaris
</li>
<li> <b>JLab</b>: Chris Cuevas, William Gu, Mark Ito
(chair), Ben Raydo, Sascha Somov
</li>
</ul>
<br>
<span class="mw-headline" id="TDC_Timing_Synchronization">TDC
Timing Synchronization</span><br>
<br>
We reviewed the <a
href="https://halldweb1.jlab.org/wiki/index.php/Proposal_on_CAEN_TDC_System_Synchronization"
title="Proposal on CAEN TDC System Synchronization">proposal</a>
for solving the 24 ns random time shifts first noticed by
Aristeidis when comparing TDC and FADC times.
<br>
<br>
<span class="mw-headline" id="The_Problem">The Problem</span><br>
<br>
With no RF signal available, we want to at least have the TDCs
tied to times of the rest of the detector. However, the CAEN
TDCs run on a 41.67 MHz clock (24 ns period). This clock is
synced to the 250 MHz detector system clock (4 ns period), but
the phase of the sync is not currently controlled. Triggers
from the detector are always synced to the 4 ns clock. When a
trigger arrives, its phase with respect to the 24 ns clock is
random and unknown. The "stop" to the TDCs is not issued until
the next rising edge of the 24 ns clock following the trigger.
This introduces a six-fold ambiguity in the time scale of the
TDCs with respect to the rest of detector.
<br>
<br>
<span class="mw-headline" id="The_Solution">The Solution</span><br>
<br>
There are many actually, but we agreed to implement the one in
the <a
href="https://halldweb1.jlab.org/wiki/index.php/Proposal_on_CAEN_TDC_System_Synchronization"
title="Proposal on CAEN TDC System Synchronization">proposal</a>,
which was worked out by William and Ben.
<br>
We still need to implement William's new TS firmware to
control the phase of the sync of the 41.67 MHz clock. We also
need to check that the TOF's TI is using the 48-bit version of
its system clock.
<br>
<br>
<span class="mw-headline" id="Work_in_the_Hall">Work in the
Hall</span><br>
<br>
Aristeidis told us that there is not much new since the last
Bi-Weekly Collaboration Meeting report, other than
improvements to the online monitoring histograms.
<br>
<br>
<span class="mw-headline" id="TOF_DAQ_Issues">TOF DAQ Issues</span><br>
<br>
Sasha O. led us through a few topics related to the read-out.
<br>
<br>
<span class="mw-headline" id="FADC_Full_Range">FADC Full Range</span><br>
<br>
He has found that the FADC-250s are set at 1 Volt full-range
rather than the 2 Volt setting he has been using at FSU. He
finds in cosmic data that 30% of the pulses are hitting the
maximum ADC value. Changing the ranges involves moving a
jumper on each board and thus removing the boards momentarily
from the crate. We agreed we should try to get this done
during the upcoming downtime while the tagger electronics are
installed in the Tagger Hall.
<br>
<br>
<span class="mw-headline"
id="Counter_Ends_and_TDC_Channel_Assignments">Counter Ends
and TDC Channel Assignments</span><br>
<br>
Sasha has noticed empirically over the last few years that he
gets better mean time performance when both ends of counter
use the same timing chip in the CAEN TDCs. He proposes for the
spring run that the assignment of channels be re-worked to
give this configuration for all counters.
<br>
<br>
<span class="mw-headline" id="FADC_Read-Out_Parameters">FADC
Read-Out Parameters</span><br>
<ul>
<li> Playing with the <b>trigger</b> versions of the
number-of-samples-before threshold-crossing (NSB) and
number-of-samples-after (NSA) seem to have no effect on
the data.
</li>
<li> Sasha O. showed <a
href="http://128.186.19.133/%7Eostrov/nsb-nsa/index.html"
class="external text" rel="nofollow">several plots</a>
of the distribution of the pulse integral in Mode 7 with
various settings of the <b>read-out</b> NSB and NSA.
Sascha S. and he discussed various possible explanations,
but we did not settle on a clear explanation for all of
the plots.
</li>
<li> Sasha O. noticed that increasing the trigger threshold
for the TOF stand-alone trigger beyond 2<sup>16</sup> has
no effect on the events. He attempted this to try and
trigger only on events with multiple TOF counters hit.
Sascha S. will check on the number of bits used by the
trigger.
</li>
</ul>
<br>
<span class="mw-headline" id="Calibration_Progress">Calibration
Progress</span><br>
<br>
Sasha O. has run into a couple of problems trying to run
through his sample of 7 million events.
<br>
<ol>
<li> He find crashes in the EVIO library for events with a
lot of hits.
</li>
<li> The code to analyze Mode 7 data crashes for unknown
reasons a few hours into the job.
</li>
</ol>
<br>
<span class="mw-headline"
id="Responsibility_for_Shift-Takers.27_Instructions">Responsibility
for Shift-Takers' Instructions</span><br>
<br>
Sasha O. had already added a lot of detail to <a
href="https://hdops.jlab.org/wiki/index.php/Time-of-Flight_System_Shift"
class="external text" rel="nofollow">the instructions</a>.
He will continue to maintain the page.
<br>
Mark also noted that there is <a
href="https://hdops.jlab.org/wiki/index.php/Information_for_Experts"
class="external text" rel="nofollow">slot on the Ops Wiki</a>
for instructions for TOF experts] which is available if more
detailed documentation is needed.
<br>
<br>
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<br>
<pre class="moz-signature" cols="72">--
Mark M. Ito, Jefferson Lab, <a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295</pre>
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