[Sbs_gems] [EXTERNAL] Hall A gas during Holiday

[Ezekiel Wertz]

Hi Kondo,

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.

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.

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.

This is merely a suggestion, sorry if it sounds like a decision.

Zeke

On Wed, Dec 15, 2021 at 5:41 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>
wrote:

> Hi Zeke,
>
> 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.
>
> 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.
>
>
>
> 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.
>
>
>
> 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.
>
>
>
> Best regards
>
> Kondo
>
>
>
> *From:* Sbs_gems <sbs_gems-bounces at jlab.org> *On Behalf Of *Ezekiel Wertz
> *Sent:* Wednesday, December 15, 2021 5:28 PM
> *To:* Sbs_gems at jlab.org
> *Cc:* Jack Segal <segal at jlab.org>
> *Subject:* [Sbs_gems] [EXTERNAL] Hall A gas during Holiday
>
>
>
> Hi GEM folks,
>
>
>
> 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.
>
>
>
> 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)?
>
>
>
> 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?
>
>
>
> 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.
>
>
>
> Best,
>
> Zeke
>
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