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<p class="MsoNormal">Hi Zeke, <o:p></o:p></p>
<p class="MsoNormal">This is fine for me. Of course you need to get input from Nilanga and Evaristo as well.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">One thing, at the beginning of cosmic data, please start with slightly lower HV on the GEMs (you and Anu/Zeke/John could make the decision how lower you want to start) to make sure that everything is OK (as expected) and after that, you
could ramp up to the nominal values. This is just a sanity check before because you are switching to a different gas system.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Good luck <o:p></o:p></p>
<p class="MsoNormal">Kondo<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> Ezekiel Wertz <ewertz@email.wm.edu> <br>
<b>Sent:</b> Monday, November 8, 2021 2:24 PM<br>
<b>To:</b> Gnanvo, Kondo (kg6cq) <kg6cq@virginia.edu><br>
<b>Cc:</b> Jack Segal <segal@jlab.org>; Bogdan Wojtsekhowski <bogdanw@jlab.org>; sbs_gems@jlab.org<br>
<b>Subject:</b> Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi GEM folks,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Particularly Nilanga and Kondo. With these clarifications, thanks Jack!, are you alright with me switching the gas from N2 to this now calibrated mixed system? This would be so the GEM layers in BigBite could flush for a couple of days
so that way an evening this week, depending on tech schedule, we could try to take cosmic data and compare it to data with premixed gas. Or do you think more discussion is required?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best,<o:p></o:p></p>
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<p class="MsoNormal">Zeke<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Mon, Nov 8, 2021 at 1:16 PM Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu">kg6cq@virginia.edu</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi Jack, <o:p></o:p></p>
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<p class="MsoNormal">Thanks for the additional information. That makes more sense because 2% level of variation would not have explained the dramatic drop that we saw, specially if 75% Ar readings actually meant 77% Ar. <o:p></o:p></p>
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<p class="MsoNormal">It would have been even higher efficiency observed <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Best regards <o:p></o:p></p>
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<p class="MsoNormal">Kondo <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span style="color:black">From:</span></b><span style="color:black"> Jack Segal <<a href="mailto:segal@jlab.org" target="_blank">segal@jlab.org</a>><br>
<b>Sent:</b> Monday, November 8, 2021 12:53 PM<br>
<b>To:</b> Gnanvo, Kondo (kg6cq) <<a href="mailto:kg6cq@virginia.edu" target="_blank">kg6cq@virginia.edu</a>>; Ezekiel Wertz <<a href="mailto:ewertz@email.wm.edu" target="_blank">ewertz@email.wm.edu</a>>; Bogdan Wojtsekhowski <<a href="mailto:bogdanw@jlab.org" target="_blank">bogdanw@jlab.org</a>><br>
<b>Cc:</b> <a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>><br>
<b>Subject:</b> Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs</span> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Kondo,<br>
I think the original attempt to use the mixing system is a little more complicated. The plumbing on the buffer<br>
tank is less than ideal. I had put it together with the view to how it would operate when things are running smoothly.<br>
I had not really thought about how it would handle something like recovering from the Argon running out, or something<br>
like that. Both the in and out of the buffer tank are on the top of the tank. So, if the mix in the buffer tank is<br>
starting out in some bad state it takes a long time for the mix in the buffer tank to reach the correct mix desired.<br>
About a day and a half to two days.<br>
My guess is we started with a bad mixture in the buffer tank and did not have enough time to clear it out.<br>
I added a purge valve on the exit of the buffer tank. So, we can valve off the delivery to the hall and force four<br>
or five cycles through the buffer tank to purge it. That will take about 20 minutes, or so.<br>
<br>
On 11/8/2021 12:43 PM, Gnanvo, Kondo (kg6cq) wrote:<br>
> Hi Zeke & Jack,<br>
> Thanks for performing the tests and summarizing the results.<br>
> <br>
> Zeke:<br>
> I am a bit confused by your statement, maybe I did not understand very well<br>
> <br>
> Is it your conclusion that the efficiency drop that we saw in the GEMs a few weeks ago is explained by the 2% disconnect between the mixture ratio readings and the actual ratio?<br>
> Best regards<br>
> Kondo<br>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------<br>
> *From:* Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> on behalf of Ezekiel Wertz <<a href="mailto:ewertz@email.wm.edu" target="_blank">ewertz@email.wm.edu</a>><br>
> *Sent:* Monday, November 8, 2021 12:16 PM<br>
> *To:* Bogdan Wojtsekhowski <<a href="mailto:bogdanw@jlab.org" target="_blank">bogdanw@jlab.org</a>><br>
> *Cc:* <a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a>>; Jack Segal <<a href="mailto:segal@jlab.org" target="_blank">segal@jlab.org</a>><br>
> *Subject:* Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs<br>
> Hi Bogdan,<br>
> <br>
> So what it seems like to me is that the different techniques used in determining the concentrations of gas are different between the manufacturer and the gas mixing system used by Jack. This ultimately leads to a 2-3% difference in the gas concentration.
<br>
> Which is about the uncertainty of the premixed gas. Since the gas system was originally 75/25, but displays the premixed system as about 77/23 or 78/22, we originally saw the GEM efficiency lower even though the mixing system was operating properly. I
<br>
> think this answers your question.<br>
> <br>
> Zeke<br>
> <br>
> On Mon, Nov 8, 2021 at 12:12 PM Bogdan Wojtsekhowski <<a href="mailto:bogdanw@jlab.org" target="_blank">bogdanw@jlab.org</a> <<a href="mailto:bogdanw@jlab.org" target="_blank">mailto:bogdanw@jlab.org</a>>> wrote:<br>
> <br>
> Looks nice. Could you summarize why the original use of the mixing system was<br>
> not successful?<br>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------<br>
> *From:* Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a> <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">mailto:sbs_gems-bounces@jlab.org</a>>> on behalf of Ezekiel Wertz <<a href="mailto:ewertz@email.wm.edu" target="_blank">ewertz@email.wm.edu</a>
<<a href="mailto:ewertz@email.wm.edu" target="_blank">mailto:ewertz@email.wm.edu</a>>><br>
> *Sent:* Monday, November 8, 2021 12:07 PM<br>
> *To:* <a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">mailto:sbs_gems@jlab.org</a>> <<a href="mailto:sbs_gems@jlab.org" target="_blank">sbs_gems@jlab.org</a> <<a href="mailto:sbs_gems@jlab.org" target="_blank">mailto:sbs_gems@jlab.org</a>>><br>
> *Cc:* Jack Segal <<a href="mailto:segal@jlab.org" target="_blank">segal@jlab.org</a> <<a href="mailto:segal@jlab.org" target="_blank">mailto:segal@jlab.org</a>>><br>
> *Subject:* [Sbs_gems] [EXTERNAL] Mixing System for GEMs<br>
> Hi GEM folks,<br>
> <br>
> I have attached a plot and will describe a discussion I had with Jack this morning pertaining to the GEM gas mix system. So if you have questions he may be able to address them better. I would like to preface that the mixing system is not connected to<br>
> the BigBite GEMs when these tests and manipulations were done.<br>
> <br>
> Recently (last couple of days) Jack was able to use the Binary Gas Analyzer, which I think analyzes the gas sample using a molecular technique. Jack would be able to provide a more accurate description of the technique. Whereas, the original mixing<br>
> system used a mass slow control based off of a voltage setpoint. What he noticed is that both systems agree pretty well.<br>
> <br>
> The plot pretty much summarizes the behavior of the GEM gas system, but I will provide a description as well. The original gas mixing system used for the GEMs was properly calibrated to 75/25 or 74/26 Ar/CO2. We see this early on in the plot (more to<br>
> the left). After this Jack then connected premix Ar/CO2 75/25, premix Ar/CO2 80/20, and 100% Argon. What we see is that with the Binary Gas Analyzer the premixed Ar/CO2 75/25 actually displays as closer to 77/23 or 78/22 for Ar/CO2. Then to the right<br>
> of the plot we see that Jack has calibrated the mixing system to be fairly identical to the premix gas value. In other words the mixing system is now calibrated to the same concentrations of Ar/CO2 as the premixed gas that the GEM folks are more<br>
> familiar with.<br>
> <br>
> So the gas system needs to flush for a couple of hours and it has been since about 10am this morning. From last week there is cosmic data using the premix system and GEM efficiencies are available. This afternoon we could switch to the mix system. Let<br>
> it flush the now calibrated mixed Ar/CO2 through the BigBite GEMs for at least 10 hours and then some time this week before returning to beam operations we could collect cosmic data and compare it to the efficiencies with the premixed gas.<br>
> <br>
> If there are any comments or questions please respond to this email.<br>
> <br>
> Best,<br>
> Zeke<br>
> <br>
<br>
-- <br>
John(Jack) Segal<br>
Halls A and C Spectrometer Support Manager<br>
Thomas Jefferson National Accelerator Facility<br>
12000 Jefferson Avenue<br>
Suite 12<br>
Newport News, VA 23606-4486<br>
Phone: (757) 269-7242<br>
Cell: (757) 320-9977<o:p></o:p></p>
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