<div dir="ltr"><div>Hi Kondo,</div><div><br></div><div>At the moment my understanding is that it is not easy to connect the GEMs to N2, with more than a 2 bottle regulator. I also think we do not have enough N2 cylinders at JLab currently to be able to support a week's worth or more of gas. Furthermore I know it is straightforward to order N2, but I am not sure if it could be guaranteed to arrive prior to the holiday break. I could be wrong on this as my understanding of the Hall A gas shed is limited and I do not know where every cylinder of N2 at JLab is located. If Jack could comment on the main reasons for staying on the mixing system, that would be greatly appreciated.</div><div><br></div><div>At current production flow rates the gas system will go through 1 Argon bottle in about 2 days and 15 days for 1 CO2 bottle. For the purposes of the holiday break the change over time for Argon is not sustainable. Even with 2 full bottles connected that change must happen once every 4 days. CO2 seems fine and I imagine it would last longer at a reduced flow rate.</div><div><br></div><div>So if we were to stick with mix, I think if we are able to reduce the flow rates for the UV layers and INFN layer we would see a significant enough drop in gas usage that it would be more reasonable for a break. I imagine going down by a factor of at least 2 or 3? I would say we just leave the UVA XY layers as unchanged, since there is concern about altering flow rates.</div><div><br></div><div>This is merely a suggestion, sorry if it sounds like a decision.<br></div><div><br></div><div>Zeke<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Dec 15, 2021 at 5:41 PM Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu">kg6cq@virginia.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Hi Zeke, <u></u><u></u></p>
<p class="MsoNormal">For the UV layers, I really don’t mind reducing the flow rate. I am pretty confident about these chambers. For the X/Y layers, I still have this marginal (probably unwarranted) worry about gas window collapsing possibility.
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<p class="MsoNormal">We have applied a fix that seems to be working extremely well so far, so it might be that I am over worrying about a non-issue but sudden pressure change in the chamber will just be a catalyst for window collapsing.
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<p class="MsoNormal">Again, I don’t want to alarm anyone because I am confident that the fix is working, I just don’t want to have to worry about the potentiality during the Xmas break.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">But even if you reduce the flow rate in the chambers and you don’t want to go down too much to preserve the low level of humidity, I think it is quite a waste to flow Ar-CO2 for a full week if we are not taking cosmic data with the chambers.
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<p class="MsoNormal">Best regards <u></u><u></u></p>
<p class="MsoNormal">Kondo<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><b>From:</b> Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> <b>On Behalf Of
</b>Ezekiel Wertz<br>
<b>Sent:</b> Wednesday, December 15, 2021 5:28 PM<br>
<b>To:</b> <a href="mailto:Sbs_gems@jlab.org" target="_blank">Sbs_gems@jlab.org</a><br>
<b>Cc:</b> Jack Segal <<a href="mailto:segal@jlab.org" target="_blank">segal@jlab.org</a>><br>
<b>Subject:</b> [Sbs_gems] [EXTERNAL] Hall A gas during Holiday<u></u><u></u></p>
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<p class="MsoNormal">Hi GEM folks,<u></u><u></u></p>
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<p class="MsoNormal">So I was able to talk to Jack today and from that discussion he plans to be in Newport News during the holiday. His current plan for the GEM gas would be to keep it on the mix Ar/CO2, but reduce the flow rate. So that way the Argon and
CO2 bottles do not run out as quickly. At the moment I think it would be nontrivial to switch the gas system to only N2 with enough cylinders to last more than a couple of days. I am also not sure we have the N2 cylinders in-hand to make this swap.<u></u><u></u></p>
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<p class="MsoNormal">For the INFN layer we typically use a standby flow of 100 cc/min per layer. Could Kondo or Nilanga comment on an acceptable reduced flow rate for the standard UV GEMs (production 600 cc/min per layer), the one UV layer with less gas flow
(production 520 cc/min per layer), and the UVA XY GEMs (225 cc/min per module)?<u></u><u></u></p>
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<p class="MsoNormal">I know Kondo had made the comment that he would prefer to not reduce the flow at all for these. But I was curious if it was possible, even if it's only a small quantity?<u></u><u></u></p>
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<p class="MsoNormal">Once a decision is made about what reduced gas flows we will use. We can then coordinate folks to change the flow meters in the Hall, once it is open before the start of the holiday break. Things already can be remotely monitored so we
can have folks do that.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Best,<u></u><u></u></p>
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<p class="MsoNormal">Zeke<u></u><u></u></p>
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