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<div class="moz-cite-prefix">Hi Folks,<br>
This will be a very interesting study!<br>
cheers,<br>
David<br>
<br>
On 2/6/22 3:12 PM, Liyanage, Nilanga K (nl8n) wrote:<br>
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Dear All</div>
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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. </div>
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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. </div>
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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.</div>
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<br>
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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</div>
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I agree with Alex that it is best to take these without zero
suppression. </div>
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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.</div>
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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.</div>
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So we must take tracking data to as high beam current as we can</div>
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Best</div>
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Nilanga</div>
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Arun: Given accelerator limits and Hall C running, how much
maximum beam current can we take ?</div>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><b>From:</b>
Sbs_gems <a class="moz-txt-link-rfc2396E" href="mailto:sbs_gems-bounces@jlab.org"><sbs_gems-bounces@jlab.org></a> on behalf of Holly
Szumila-Vance <a class="moz-txt-link-rfc2396E" href="mailto:hszumila@jlab.org"><hszumila@jlab.org></a><br>
<b>Sent:</b> Sunday, February 6, 2022 10:45 AM<br>
<b>To:</b> Rathnayake, Anuruddha (adr4zs)
<a class="moz-txt-link-rfc2396E" href="mailto:adr4zs@virginia.edu"><adr4zs@virginia.edu></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a> <a class="moz-txt-link-rfc2396E" href="mailto:Sbs_gems@jlab.org"><Sbs_gems@jlab.org></a>; Arun
Tadepalli <a class="moz-txt-link-rfc2396E" href="mailto:arunts@jlab.org"><arunts@jlab.org></a><br>
<b>Subject:</b> Re: [Sbs_gems] [EXTERNAL] Upper limits in
terms of beam current for the GEM study planned for tomorrow</font>
<div> </div>
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<div dir="auto">
<div dir="ltr">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. </div>
<div dir="ltr"><br>
<blockquote type="cite">On Feb 6, 2022, at 9:52 AM, Anuruddha
Rathnayake <a class="moz-txt-link-rfc2396E" href="mailto:adr4zs@virginia.edu"><adr4zs@virginia.edu></a> wrote:<br>
<br>
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<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">Dear All,<br>
<br>
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. <br>
<br>
I'm attaching the GEM linearity studies we have done so
far, if that helps to make a decision. <a
href="https://logbooks.jlab.org/entry/3932489"
moz-do-not-send="true" class="moz-txt-link-freetext">https://logbooks.jlab.org/entry/3932489</a><br>
<br>
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).<br>
<br>
Best,<br>
Anu<br>
<br>
</div>
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