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<article id="node-1398320" class="node node-logentry article ia-n clearfix" role="article">
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<a href="https://logbooks.jlab.org/entry/4325262" rel="bookmark">Hall B possible contamination in 4K supply circuit</a>
</h1>
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<p class="author-datetime">
Lognumber <a href="https://logbooks.jlab.org/entry/4325262" class="lognumber" data-lognumber="4325262">4325262</a>. Submitted by <a href="https://logbooks.jlab.org/user/kashy">kashy</a> on <time datetime="2025-01-06T16:36:00-0500" pubdate="pubdate"><a href="https://logbooks.jlab.org/entries?start_date=1736195760&end_date=1736202960&book=HBLOG&book=HBTORUS&book=CLOG">Mon, 01/06/2025 - 16:36</a></time>. </p>
<p class="last-update">
Last updated on <time datetime="2025-01-06T16:38:18-0500" pubdate="pubdate">Mon, 01/06/2025 - 16:38</time> </p>
<table class="field-vitals">
<tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/hblog">HBLOG</a> <a href="https://logbooks.jlab.org/book/hbtorus">HBTORUS</a> <a href="https://logbooks.jlab.org/book/clog">CLOG</a></td></tr>
<tr><th>Entry Makers: </th><td>Kashy</td></tr>
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<div class="logentry node-content">
<p>While writing a procedure to disconnect the Hall B Buffer Dewar (which is not needed for upcoming run or the following run) I noticed that the 4K supply pressure as read on PT8512 is reading 0.99 atm.<br />
Plotting it I found that since July 2024 this pressure has dropped below 1.00 atm ~6 times with the lowest value being 0.66atm and this slowly rose for 13 days back to 1 atm (see plot attached). it is not clear if the pressure rose due to temperature rise, helium flow through a leaky valve or an air leak. </p>
<p>Also of importance is that the data logger has not taken data since December 1 when the pressure read 0.9atm. Today it is reading 0.99 and even this alarmed me. I went ahead and set the LOLO alarm value to 1.02atm and made this a MAJOR Alarm. This needs to be put on the Hall B tech ON-CALL pager!</p>
<p>I have checked the pressures in the 4K supply circuits of the Torus and Solenoid over the same period none of the data available up to 12/1/24 shows their supply circuit going sub-atmospheric. This is good news.<br />
At minimum, we must warm and purge 4K circuit of the DBX and the ESMTL to Hall B prior to magnet cooldown. We also need to consider how to verify no water ice has built up on the isolation valves PV8512S and PV8512T.</p>
<p>Tomorrow I will start to work on a plan for this tomorrow and circulate it when it is ready to share.</p>
<p>Dave</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/2025/01/4325262/Screenshot (621).png" width="960" height="540" alt="" title="4K supply pressure in the DBX" /></div> <div class="image-wrapper"><img view_mode="elog_email" class="image-style-plentybig" src="https://logbooks.jlab.org/files/styles/plentybig/public/2025/01/4325262/4K supply pressure DS of the DBX.png" width="960" height="540" alt="" title="4K supply pressure in the Torus and Solenoid" /></div> </div>
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