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</style><article id="node-701521" 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/3628625" rel="bookmark">FCAL LED pulser</a>
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Lognumber <a href="https://logbooks.jlab.org/entry/3628625" class="lognumber" data-lognumber="3628625">3628625</a>. Submitted by <a href="https://logbooks.jlab.org/user/somov">somov</a> on <time datetime="2018-11-19T17:44:46-0500" pubdate="pubdate"><a href="https://logbooks.jlab.org/entries?start_date=1542663886&end_date=1542671086&book=HDFCAL&book=HDLOG&book=HDTRIGGER">Mon, 11/19/2018 - 17:44</a></time>. </p>
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Last updated on <time datetime="2018-11-19T17:45:28-0500" pubdate="pubdate">Mon, 11/19/2018 - 17:45</time></p>
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<div class="ctools-collapsible-container"><div class="ctools-collapsible-handle"><a href="#">There is 1 comment...</a></div><div class="ctools-collapsible-content"><a id="comment-18673"></a>
<article class="comment comment-new odd first clearfix"><header class="comment-header"><h3 class="comment-title">
<a href="https://logbooks.jlab.org/comment/18673#comment-18673" rel="bookmark">Sasha, is this for the</a> </h3>
<em class="new">new</em>
</header><footer class="submitted"><p class="author-datetime">by <a href="https://logbooks.jlab.org/user/gleasonc" title="View user profile." class="username">gleasonc</a> on <time datetime="2018-11-19T18:18:07-0500" pubdate="pubdate">Mon, 11/19/2018 - 18:18</time></p>
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<div class="field field-name-comment-body field-type-text-long field-label-hidden view-mode-elog_email"><div class="field-items"><div class="field-item even"><p>Sasha, is this for the standard production HV settings? Or are all channels set to the same HV?</p>
<p>One thing you will need to keep in mind around the beam hole when using LEDs is the amount of radiation damage in each block (see this image <a href="https://halldweb.jlab.org/wiki/images/e/ea/4x4_array.pdf">https://halldweb.jlab.org/wiki/images/e/ea/4x4_array.pdf</a> for an image of radiation damage for each channel around the beam hole). The lower amplitude of the bottom row could be due to radiation damage and not a "wrong" HV set point (we know it's wrong in the sense that it is uncalibrated, but there may only be a small correction needed). For this row (27_30,27_29, and 27_28), the HV is set to the max EPICS value of 1800V with the production settings. </p>
<p> It would be interesting to check this with the green pulser, at say 25V, as that is not affected as much by the radiation damage. Nonetheless, I look forward to seeing the result with properly tuned HV.</p>
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<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/hdfcal">HDFCAL</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</td></tr></table></div>
<div class="logentry node-content">
<p>FCAL FADC waveforms for 3 inner FCAL layers induced by a violet LED pulser operated at 15 V<br />
(data is taken in a raw fadc mode). Each histogram represents the FCAL module. Histograms are<br />
normalized to 500 fadc counts. FADC amplitudes have different peak values even in the 3rd FCAL<br />
layer, which can be accounted for either different light collection or PMT gains<br />
(we'll correlate amplitudes with the calibration coefficient obtained by Iliya).</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/2018/11/3628625/fcal_3inner_layers.png" width="960" height="960" alt="" title="Fig. 1 FCAL signal waveforms induced by a violet LED pulser operated at 15 V" /></div> </div>
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