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<p class="MsoNormal">Nilanga, <o:p></o:p></p>
<p class="MsoNormal">I think it is better to keep flushing with N2 rather than seal the chambers If we can afford that.
<o:p></o:p></p>
<p class="MsoNormal">This will keep the chamber dry all the time reducing the risk of destructive sparks due to humidity whenever we decide to apply HV
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards <o:p></o:p></p>
<p class="MsoNormal">Kondo<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Sbs_gems <sbs_gems-bounces@jlab.org> <b>On Behalf Of
</b>Liyanage, Nilanga K (nl8n)<br>
<b>Sent:</b> Wednesday, February 9, 2022 3:42 PM<br>
<b>To:</b> Holly Szumila-Vance <hszumila@jlab.org>; nilanga@jlab.org<br>
<b>Cc:</b> Sbs_gems@jlab.org<br>
<b>Subject:</b> [Sbs_gems] [EXTERNAL] Re: Question about BB GEM plan during SAD<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">HI Holly,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I think it would be better to first install the filters and then switch to N2; this way any dust created during the switch over would be captured. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">BTW: Before the filters are installed in the line to the chambers, they should be hooked up in some other line (N2 is OK for this) and flushed for a couple of hours. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">So I am assuming that you plan to run N2 during the whole SAD period, right ? In this case we must make sure that the bottles do not run empty. Since the output end is open, if the flow stops,
we can have back diffusion contaminating the chambers. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">(Kondo: Do you think it is better to run N2 during the down, or to seal the chambers with no gas flow ?)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I believe we sent all 4 upgraded HV divider boards to Jlab. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">We also plan to test the power supply with an individual channel for each electrode in the GEM. Evaristo has also sent a similar supply which could power 2 chambers. So altogether we will have
such supplies for 3 front layers (these are best to used these in the front UV layers, because they see the highest rate and have the largest area) . While the new dividers will give us a factor of 2 improvement, these power supplies will give a factor of
8 or more. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">So it would be best if we equip the first 3 UV chambers with these supplies, and use the new divider on the 4<sup>th</sup> chamber.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">So it would be great if you could wait a couple of weeks till we test the individual power supply and then decide in the installation schedule.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Best<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Nilanga<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black">From:</span></b><span style="color:black"> Holly Szumila-Vance <<a href="mailto:hszumila@jlab.org">hszumila@jlab.org</a>><br>
<b>Sent:</b> Wednesday, February 9, 2022 12:42 PM<br>
<b>To:</b> <a href="mailto:nilanga@jlab.org">nilanga@jlab.org</a> <<a href="mailto:nilanga@jlab.org">nilanga@jlab.org</a>><br>
<b>Cc:</b> <a href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a> <<a href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a>><br>
<b>Subject:</b> Question about BB GEM plan during SAD</span> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="xmsonormal"><span style="font-size:11.0pt">Hi Nilanga,</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt">We have a few questions about the plan for the BB GEMs during the SAD.
</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<li class="xmsolistparagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Currently, they are still running production gas. I’d like to install the gas line filters. Should we keep them on production and take cosmics when
we install the filters? Is there any other consideration here?</span><o:p></o:p></li><li class="xmsolistparagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Once we’ve installed the filters, I think we want to proceed with having them on nitrogen and figuring out a plan to install the HV divider. I think
we currently have one on site. Without beam, are there any other tests that we should perform besides an HV runup? This will probably require lots of coordination with Jessie’s hall work.
</span><o:p></o:p></li><li class="xmsolistparagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Is there any other work/upgrades/considerations for these GEMs besides the two questions above?</span><o:p></o:p></li></ol>
<p class="xmsonormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt">Thanks,</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt">Holly</span><o:p></o:p></p>
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