[Sbs_gems] [EXTERNAL] Re: Question about BB GEM plan during SAD

[Liyanage, Nilanga K (nl8n)]

HI Holly,

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.

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.

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.

(Kondo: Do you think it is better to run N2 during the down, or to seal the chambers with no gas flow ?)

I believe we sent all 4 upgraded HV divider boards to Jlab.

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.

So it would be best if we equip the first 3 UV chambers with these supplies, and use the new divider on the 4th chamber.

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.

Best

Nilanga

________________________________
From: Holly Szumila-Vance <hszumila at jlab.org>
Sent: Wednesday, February 9, 2022 12:42 PM
To: nilanga at jlab.org <nilanga at jlab.org>
Cc: Sbs_gems at jlab.org <Sbs_gems at jlab.org>
Subject: Question about BB GEM plan during SAD


Hi Nilanga,



We have a few questions about the plan for the BB GEMs during the SAD.



  1.  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?
  2.  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.
  3.  Is there any other work/upgrades/considerations for these GEMs besides the two questions above?



Thanks,

Holly
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