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</style><article id="node-718841" class="node node-logentry contextual-links-region article ia-n clearfix" role="article"><header class="node-header"><h1 class="node-title">
<a href="https://logbooks.jlab.org/entry/3645931" rel="bookmark">CCAL LED/ALPHA trigger adjustment</a>
</h1>
</header><div class="contextual-links-wrapper"><ul class="contextual-links"><li><a href="https://logbooks.jlab.org/entry/3645931/edit?destination=email/send">Edit</a></li><li><a href="https://logbooks.jlab.org/entry/3645931/delete?destination=email/send">Delete</a></li></ul></div>
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<p class="author-datetime">
Lognumber <a href="https://logbooks.jlab.org/entry/3645931" class="lognumber" data-lognumber="3645931">3645931</a>. Submitted by <a href="https://logbooks.jlab.org/user/somov">somov</a> on <time datetime="2019-01-27T23:45:13-0500" pubdate="pubdate"><a href="https://logbooks.jlab.org/entries?start_date=1548647113&end_date=1548654313&book=HDCCAL&book=HDLOG&book=HDTRIGGER">Sun, 01/27/2019 - 23:45</a></time>. </p>
<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/hdccal">HDCCAL</a> <a href="https://logbooks.jlab.org/book/hdlog">HDLOG</a> <a href="https://logbooks.jlab.org/book/hdtrigger">HDTRIGGER</a></td></tr><tr><th>Entry Makers: </th><td>somov, berdnik</td></tr></table></div>
<div class="logentry node-content">
<p>We adjusted LED and Alpha triggers for two reference PMTs.<br />
Each CCAL reference PMT detects light from the LED optical<br />
fiber and YAP:Ce Am source (alpha source trigger) attached<br />
to the PMT face.</p>
<p>1. LED trigger is generated by the CAEN 1495 module and<br />
is distributed to the TS front panel (bit 5).</p>
<p>2. The alpha trigger is produced by each reference PMT<br />
(we OR triggers from two PMTs). We use NIM modules to veto<br />
PMT signals induced by the LED pulser, and select<br />
alpha-source signals only. The alpha-source trigger is<br />
subsequently sent to the TS FP ( bit 6 ). The trigger rate is 120 Hz<br />
(the discriminator threshold was set to 25 mV).</p>
<p>3. We adjusted HV on each reference PMT in such a way,<br />
that both, the LED and alpha-source signals are within<br />
the fadc amplitude range. The LED bias voltage was set to the<br />
maximum value of 29 V.</p>
<p>HV (reference PMT1) = 850 V<br />
HV (reference PMT2) = 790 V</p>
<p>Fig. 1 FADC waveforms induced by an LED trigger (TS FP bit 5)<br />
The first pulse (around fadc sample 38) corresponds to<br />
the noise in the LED distribution system, and has to be reduced. </p>
<p>Fig. 2 and Fig. 3. FADC waveforms induced by an Am alpha source.</p>
<p>Fig. 4 and Fig. 5. FADC peak amplitude for the LED and alpha source<br />
for two reference PMTs</p>
<p>Fig. 6 FADC peak amplitude produced by alpha sources for two PMTs<br />
(zoom in distribution).</p>
<p>------------------------</p>
<p>run 60289 (data1) LED (TS FP bit 5 only)<br />
run 60291 (data3) Alpha trigger (TS FP bit 6 only)</p>
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<div class="image-wrapper"><img view_mode="elog_email" class="image-style-plentybig" src="https://logbooks.jlab.org/files/styles/plentybig/public/2019/01/3645931/led_waveform.png" width="960" height="591" alt="" title="Fig. 1 FADC waveforms induced by an LED trigger (TS FP bit 5)" /></div> </div>
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