[Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow

Mark Jones jones at jlab.org
Mon Feb 7 12:24:18 EST 2022 

Since Hall C is at max 70 that is 350 so that leaves 80uA/2pass = 40uA max for
Hall A. There will probably be more RF trips. So you may want to talk to Hall A
to see if there is dummy running ( 40uA)  needed that could work at that time.

Cheers,
          Mark
________________________________
From: Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of David Flay <flay at jlab.org>
Sent: Monday, February 7, 2022 12:09 PM
To: Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu>; Arun Tadepalli <arunts at jlab.org>
Cc: sbs_gems at jlab.org <Sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow

Hi Nilanga,

I believe the total current allowed in the machine is 430 uA -- so this accounts for beam passes.  In other words, certainly have to negotiate with Hall C depending on where they are in terms of beam-pass.

Best regards,
David

----------------------------------------------------------------
David Flay, Ph. D.
Hall A/C Staff Scientist
Thomas Jefferson National Accelerator Facility
Office: CEBAF Center, C119
----------------------------------------------------------------


________________________________
From: Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu>
Sent: Monday, February 7, 2022 12:05 PM
To: Arun Tadepalli <arunts at jlab.org>
Cc: sbs_gems at jlab.org <sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow

Hi Arun

Thanks for that information.

It is nice to see that we are allowed to go up to 70 uA with the cryo targets.

But the question is what will hall C be taking during that time ?

What is the  maximum current the accelerator could deliver  at this time ?

If we are going to hit this upper limit of the total current, then you  will have to negotiate with Hall C to see if they agree to lower their current for an hour or two while we take out data.

Best

Nilanga
________________________________
From: Arun Tadepalli <arunts at jlab.org>
Sent: Monday, February 7, 2022 11:59 AM
To: Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu>
Cc: sbs_gems at jlab.org <sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow

Hello GEM folks,

I sent a snapshot of max current per target as per the OR document. Any update on what current you would like to go to? I’d have to give a heads up to other halls on our plans.

Best,

Arun

On Feb 6, 2022, at 11:38 PM, Arun Tadepalli <arunts at jlab.org<mailto:arunts at jlab.org>> wrote:

Dear Nilanga,

Please find attached a snapshot from the operational restrictions document for Hall A. It contains the maximum allowable CW current on each target.

Best,

Arun

<OR_max_current.png>

On Feb 6, 2022, at 4:19 PM, David Armstrong <armd at jlab.org<mailto:armd at jlab.org>> wrote:

Hi Folks,
   This will be a very interesting study!
 cheers,
   David

On 2/6/22 3:12 PM, Liyanage, Nilanga K (nl8n) wrote:
Dear All

My objectives for the high current study are to learn about challenges in high occupancy running such as pileups in both time and space,  two signals on the same strip separated by a short time) and two  hits on nearby strips causing the clusters to merge. Even if we solve all hardware problems like gain drop, we are sure to be limited by the occupancy issues in GEp.

Like Kondo said the highest beam current we can take will be limited by the 1 mA limit on the GEM power supplies. The baseline GEM current is about 735 uA, and we are running around 780 uA now  (with 5 uA of beam current on LH2) ;  this is about 45 uA excess current in GEM. Given this  we should be able to go five  times higher or more in beam current before we hit this limit.

So I would like to try to go up to 25 uA on LH2 and also on LD2, if we can get those beam currents.

We can do this in a few steps, say 5 uA steps in beam current. All we need are short runs, say 10 min at each setting

I agree with Alex that it is best to take these without zero suppression.

As Kondo suggested, at each setting we can first take a run with only one UV chamber turned on. After that run, if things look OK, turn the rest of the GEMs and take another run, and then repeat this procedure at the rest of the beam currents.

If we only take  the high current runs with only one chamber on, and not take the tracking runs with the other chambers on, then there is nothing we can learn about pileup and this exercise would not be very useful.

So we must take tracking data to as high beam current as we can

Best

Nilanga

Arun: Given accelerator limits and Hall C running, how much maximum beam current can we take ?



________________________________
From: Sbs_gems <sbs_gems-bounces at jlab.org><mailto:sbs_gems-bounces at jlab.org> on behalf of Holly Szumila-Vance <hszumila at jlab.org><mailto:hszumila at jlab.org>
Sent: Sunday, February 6, 2022 10:45 AM
To: Rathnayake, Anuruddha (adr4zs) <adr4zs at virginia.edu><mailto:adr4zs at virginia.edu>
Cc: Sbs_gems at jlab.org<mailto:Sbs_gems at jlab.org> <Sbs_gems at jlab.org><mailto:Sbs_gems at jlab.org>; Arun Tadepalli <arunts at jlab.org><mailto:arunts at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow

To be clear, the question is what current limits are we willing to test up to for the gem test tomorrow on swing- probably a question for Nilanga and/or Kondo. I think this is for coordination with MCC purposes.

On Feb 6, 2022, at 9:52 AM, Anuruddha Rathnayake <adr4zs at virginia.edu><mailto:adr4zs at virginia.edu> wrote:


Dear All,

There is a discussion going on between our current RC (Arun) and some of us here in Jlab about what would be the beam current limits that we should adhere to, if it is possible to come into such a limit looking at the observations we have made so far.

I'm attaching the GEM linearity studies we have done so far, if that helps to make a decision. https://logbooks.jlab.org/entry/3932489

I believe if you use linearity studies done at SBS-11, that would be the best as our current spectrometer angles at SBS-9 are similar to what we had at SBS-9 (Please correct me if I am wrong, I know this more of as a word of mouth rather than referring to any official documentation).

Best,
Anu

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