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</style><article id="node-1035929" 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/3962905" rel="bookmark">GEM related work during Access</a>
</h1>
</header><div class="contextual-links-wrapper"><ul class="contextual-links"><li><a href="https://logbooks.jlab.org/entry/3962905/edit?destination=email/send">Edit</a></li><li><a href="https://logbooks.jlab.org/entry/3962905/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/3962905" class="lognumber" data-lognumber="3962905">3962905</a>. Submitted by <a href="https://logbooks.jlab.org/user/ewertz">ewertz</a> on <time datetime="2021-12-14T12:15:55-0500" pubdate="pubdate"><a href="https://logbooks.jlab.org/entries?start_date=1639498555&end_date=1639505755&book=HALOG">Tue, 12/14/2021 - 12:15</a></time>. </p>
<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/halog">HALOG</a></td></tr><tr><th>Entry Makers: </th><td>hszumila</td></tr></table></div>
<div class="logentry node-content">
<p>Today we had an opportunistic access and we started with removing INFN J2. It was survey by RadCon and moved to EEL 126, and we placed it in its own radiation zone. That was interesting since we took it through the labyrinth and up the elevator. Thanks to the folks who helped with that. </p>
<p>The next thing we did was check if the HV supply was the source of the problem for J0 bot. We swapped it to another channel on the CAEN HV supply and we saw a similar current as the first channel. This leads me to conclude that the HV supply is most likely fine and that the source of this problem is due to a problem with the HV divider on the bottom module. We tried to look at the divider and though it is not covered in shielding. So it could be replaced. The amount of time to check and replace the module would not be worth the needed downtime. It would also require us disconnect the layer and move it on the rails. This would require us going up in a lift to remove the top safety pin and safe access from the ground via a ladder. The current locations of BigBite and SBS make this nearly impossible. At this time Holly and I do not think it is worthwhile or possible to pursue the divider change while J0 is in BigBite. </p>
<p>The last thing I worked on was power-cycling the INFN LV supply and we found the channel connected to J0 in a bizarre (tripped) state. We think this is most likely due to when the HV from the GEM zapped an APV card. Not confirmed, but pretty sure. Anyway power-cycling brought it back around. I also put the entire supply on a remote power strip. I know the IP address, but I still need to find the proper credentials. I then disconnected cables on the backplane of J0 bottom that sits close to the HV divider, where the zapped APV lives. The reason for this is that APV misconfigures all other APVs on that MPD (kind of like an old string of tree lights). So disconnecting the HDMIs and the LV cables at the backplane effectively bypasses that APV. It is not enough to simply disable that APV from the DAQ, but I have disabled all middle and bottom module APVs in the DAQ. I need to take some pedestal data to verify that the DAQ will be happy with J0 Top electronics, but that objective is straightforward.</p>
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