[Sbs_gems] [EXTERNAL] Mixing System for GEMs

Mon Nov 8 14:35:45 EST 2021

Hi Kondo,

Thanks for those comments. I will be sure to check with Evaristo as well,
though I think he is on this email chain, but there is a time difference. I
don't think I stated it in past emails, but I would start at maybe 3800 V
or 3900 V and then begin to ramp in like increments of 500 V to the desired
equivalent values of 4100 V or previously defined voltage setpoints. If we
wanted to we even could take data at different HV settings to try and make
some sort of efficiency curve. But I would have to think about how much
cosmic data we would need for that.

Zeke

On Mon, Nov 8, 2021 at 2:29 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
wrote:

> Hi Zeke,
>
> This is fine for me. Of course you need to get input from Nilanga and
> Evaristo as well.
>
>
>
> 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.
>
>
>
> Good luck
>
> Kondo
>
>
>
> *From:* Ezekiel Wertz <ewertz at email.wm.edu>
> *Sent:* Monday, November 8, 2021 2:24 PM
> *To:* Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
> *Cc:* Jack Segal <segal at jlab.org>; Bogdan Wojtsekhowski <bogdanw at jlab.org>;
> sbs_gems at jlab.org
> *Subject:* Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs
>
>
>
> Hi GEM folks,
>
>
>
> 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?
>
>
>
> Best,
>
> Zeke
>
>
>
>
>
>
>
> On Mon, Nov 8, 2021 at 1:16 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
> wrote:
>
> Hi Jack,
>
> 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.
>
> It would have been even higher efficiency observed
>
>
>
> Best regards
>
> Kondo
>
>
> ------------------------------
>
> *From:* Jack Segal <segal at jlab.org>
> *Sent:* Monday, November 8, 2021 12:53 PM
> *To:* Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>; Ezekiel Wertz <
> ewertz at email.wm.edu>; Bogdan Wojtsekhowski <bogdanw at jlab.org>
> *Cc:* sbs_gems at jlab.org <sbs_gems at jlab.org>
> *Subject:* Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs
>
>
>
> Kondo,
>    I think the original attempt to use the mixing system is a little more
> complicated. The plumbing on the buffer
> tank is less than ideal. I had put it together with the view to how it
> would operate when things are running smoothly.
> I had not really thought about how it would handle something like
> recovering from the Argon running out, or something
> 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
> starting out in some bad state it takes a long time for the mix in the
> buffer tank to reach the correct mix desired.
> About a day and a half to two days.
>    My guess is we started with a bad mixture in the buffer tank and did
> not have enough time to clear it out.
>    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
> or five cycles through the buffer tank to purge it. That will take about
> 20 minutes, or so.
>
> On 11/8/2021 12:43 PM, Gnanvo, Kondo (kg6cq) wrote:
> > Hi Zeke & Jack,
> > Thanks for performing the tests and summarizing the results.
> >
> > Zeke:
> > I am a bit confused by your statement, maybe I did not understand very
> well
> >
> > 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?
> > Best regards
> > Kondo
> >
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> > *From:* Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of Ezekiel Wertz
> <ewertz at email.wm.edu>
> > *Sent:* Monday, November 8, 2021 12:16 PM
> > *To:* Bogdan Wojtsekhowski <bogdanw at jlab.org>
> > *Cc:* sbs_gems at jlab.org <sbs_gems at jlab.org>; Jack Segal <segal at jlab.org>
> > *Subject:* Re: [Sbs_gems] [EXTERNAL] Mixing System for GEMs
> > Hi Bogdan,
> >
> > 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.
> > 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
> > think this answers your question.
> >
> > Zeke
> >
> > On Mon, Nov 8, 2021 at 12:12 PM Bogdan Wojtsekhowski <bogdanw at jlab.org <
> mailto:bogdanw at jlab.org <bogdanw at jlab.org>>> wrote:
> >
> >     Looks nice. Could you summarize why the original use of the mixing
> system was
> >     not successful?
> >
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >     *From:* Sbs_gems <sbs_gems-bounces at jlab.org <
> mailto:sbs_gems-bounces at jlab.org <sbs_gems-bounces at jlab.org>>> on behalf
> of Ezekiel Wertz <ewertz at email.wm.edu <mailto:ewertz at email.wm.edu
> <ewertz at email.wm.edu>>>
> >     *Sent:* Monday, November 8, 2021 12:07 PM
> >     *To:* sbs_gems at jlab.org <mailto:sbs_gems at jlab.org
> <sbs_gems at jlab.org>> <sbs_gems at jlab.org <mailto:sbs_gems at jlab.org
> <sbs_gems at jlab.org>>>
> >     *Cc:* Jack Segal <segal at jlab.org <mailto:segal at jlab.org
> <segal at jlab.org>>>
> >     *Subject:* [Sbs_gems] [EXTERNAL] Mixing System for GEMs
> >     Hi GEM folks,
> >
> >     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
> >     the BigBite GEMs when these tests and manipulations were done.
> >
> >     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
> >     system used a mass slow control based off of a voltage setpoint.
> What he noticed is that both systems agree pretty well.
> >
> >     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
> >     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
> >     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
> >     familiar with.
> >
> >     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
> >     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.
> >
> >     If there are any comments or questions please respond to this email.
> >
> >     Best,
> >     Zeke
> >
>
> --
> John(Jack) Segal
> Halls A and C Spectrometer Support Manager
> Thomas Jefferson National Accelerator Facility
> 12000 Jefferson Avenue
> Suite 12
> Newport News, VA 23606-4486
> Phone: (757) 269-7242
> Cell: (757) 320-9977
>
>
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