<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi George,<div class=""><br class=""></div><div class="">Do you think the 2.1 limit can be increased or is it too dangerous?</div><div class="">It seems to me that c4f10 in the bubbler may be "the" main cause of gas losses. Please correct if I'm wrong.</div><div class=""><br class=""></div><div class="">The scale stayed at 71 for almost 3 days. This indicates a leak rate of 0.3 Kg / day, which is what was predicted, however I believe the box performs even better than this since David patched a couple of places.</div><div class=""><br class=""></div><div class="">Results on the gas on the data coming soon, I apologize it's taking so long.</div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Mauri</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="CA08B002-88F4-4B70-9653-230439CA2AB2" src="cid:15A7C78F-B8E8-4540-A6CB-C0CBCE5B6315@jlab.org" class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 5, 2018, at 10:48 AM, George Jacobs <<a href="mailto:jacobsg@jlab.org" class="">jacobsg@jlab.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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Hi Mauri,<br class="">
<br class="">
Current Status -From the pressure strip chart, it looks as if the
detector has been full since around noon on 29 Jan. The best way to
determine the detector fill is from the detector monitor or event
plots.<br class="">
<br class="">
<div class="">Gas Usage - From the gas supply remaining as indicated by the
scale readout, usage since 30 Jan is 3 kg or 0.5 kg per day<br class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">The detector pressure is limited to 2.1"wc by the bubblers,
ambient pressure changes or transients are a significant factor in
gas loss.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">I have attached the strip chart showing the detector pressure
and ambient pressure history.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">Blue line is gas pressure at the bottom of the detector.<br data-mce-bogus="1" class="">
</div>
<div class="">Brown line show pressure at the bubbler.<br data-mce-bogus="1" class="">
</div>
<div class="">Green line is ambient pressure.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">22 Jan - gas flow started @ 0.5 slm<br data-mce-bogus="1" class="">
</div>
<div class="">29 Jan - Detector volume indicates it is FULL<br data-mce-bogus="1" class="">
</div>
<div class="">29 Jan - gas flow reduced to 0.1 slm<br data-mce-bogus="1" class="">
</div>
<div class="">30 Jan - gas flow reduced to 0.065 slm (65 sccm)<br data-mce-bogus="1" class="">
</div>
<div class="">31 Jan - Gas supply programmed to shut off when pressure
reaches 2.02"wc and turn back on when it falls to 1.95"wc<br class="">
<br class="">
<span id="cid:part1.23361C6D.01722014@jlab.org"><LTCC-S5-Press-05Feb2018-2.png></span><br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">Detector pressure rises and falls as ambient pressure changes.
Ambient pressure changes are significant when compared with
detector pressure. </div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">When ambient pressure decreases, detector differential pressure
increases. When the detector pressure exceeds 2.1"wc, gas is lost
out the bubbler. This gas loss is significant.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">When ambient pressure increases, detector differential pressure
decreases. The magnitude of the pressure decrease follows that of
the ambient pressure change and is countered by the gas flow.
Current gas flow is set at 65 sccm, the minimum flow the mass flow
controllers can achieve. A higher flow would help minimize the
magnitude of the pressure decrease. A higher flow would also
increase gas usage or loss out the bubbler, during an ambient
pressure decrease.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">Determining the maintenance gas flow rate is a balancing act.
Increasing the gas flow would minimize the detector pressure
decrease during ambient pressure transients, but would also
increase gas usage or loss rate. A good reason to increase gas
flow would be to verify proper detector operation at the current
flow rate.<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
<div class="">Everything looks good from what the pressure strip chart shows.
Has anyone looked at the events from beam as yet?<br data-mce-bogus="1" class="">
</div>
<div class=""><br data-mce-bogus="1" class="">
</div>
George<br class="">
<br class="">
<pre class="moz-signature" cols="72">--
George Jacobs
Jefferson Lab (TJNAF)
STE 12
12000 Jefferson Ave.
Newport News, VA 23606
(office) 757-269-7115
(cell) 757-876-0480
(email) <a class="moz-txt-link-abbreviated" href="mailto:jacobsg@jlab.org">jacobsg@jlab.org</a>
(website) <a class="moz-txt-link-freetext" href="https://userweb.jlab.org/~jacobsg">https://userweb.jlab.org/~jacobsg</a></pre>
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