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

Mon Feb 7 13:08:24 EST 2022

Hi Nilanga,

Just to be sure, are you still planning to be in the counting house and
guide us during this test?
I will plan to be in the counting house when the test happens.

Best,
Anuruddha

On Mon, 7 Feb 2022, 13:05 Liyanage, Nilanga K (nl8n), <nl8n at virginia.edu>
wrote:

>
> OK sounds good Arun
>
> I think it would be important to take LH2 or LD2 runs
>
> Best
>
> Nilang
> ------------------------------
> *From:* Arun Tadepalli <arunts at jlab.org>
> *Sent:* Monday, February 7, 2022 12:28 PM
> *To:* Mark Jones <jones at jlab.org>
> *Cc:* David Flay <flay at jlab.org>; Liyanage, Nilanga K (nl8n) <
> nl8n at virginia.edu>; 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 Nilanga,
>
> From negotiations perspective, Hall C is ok bumping down their current to
> provide us 25 uA and this can happen comfortably. Il bring up the
> possibility of dummy running to avoid RF trips during this time but even if
> not, we can get what we ask for.
>
> Best,
>
> Arun
>
> On Feb 7, 2022, at 12:24 PM, Mark Jones <jones at jlab.org> wrote:
>
> 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> 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> 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> <sbs_gems-bounces at jlab.org> on
> behalf of Holly Szumila-Vance <hszumila at jlab.org> <hszumila at jlab.org>
> *Sent:* Sunday, February 6, 2022 10:45 AM
> *To:* Rathnayake, Anuruddha (adr4zs) <adr4zs at virginia.edu>
> <adr4zs at virginia.edu>
> *Cc:* Sbs_gems at jlab.org <Sbs_gems at jlab.org> <Sbs_gems at jlab.org>; Arun
> Tadepalli <arunts at jlab.org> <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>
> <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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