<div dir="ltr">Hi Arun,<div><br></div><div>I think this is the response you are looking for from Nilanga. I think he forgot to include you when he sent it.</div><div><br></div><div>Best,<br>Sean<br><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">---------- Forwarded message ---------<br>From: <strong class="gmail_sendername" dir="auto">Liyanage, Nilanga K (nl8n)</strong> <span dir="auto"><<a href="mailto:nl8n@virginia.edu">nl8n@virginia.edu</a>></span><br>Date: Sun, Feb 6, 2022 at 3:12 PM<br>Subject: Re: [Sbs_gems] [EXTERNAL] Upper limits in terms of beam current for the GEM study planned for tomorrow<br>To: Holly Szumila-Vance <<a href="mailto:hszumila@jlab.org">hszumila@jlab.org</a>>, Rathnayake, Anuruddha (adr4zs) <<a href="mailto:adr4zs@virginia.edu">adr4zs@virginia.edu</a>><br>Cc: <a href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a> <<a href="mailto:Sbs_gems@jlab.org">Sbs_gems@jlab.org</a>><br></div><br><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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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="m_5330301851014143411divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Sbs_gems <<a href="mailto:sbs_gems-bounces@jlab.org" target="_blank">sbs_gems-bounces@jlab.org</a>> on behalf of Holly Szumila-Vance <<a href="mailto:hszumila@jlab.org" target="_blank">hszumila@jlab.org</a>><br>
<b>Sent:</b> Sunday, February 6, 2022 10:45 AM<br>
<b>To:</b> Rathnayake, Anuruddha (adr4zs) <<a href="mailto:adr4zs@virginia.edu" target="_blank">adr4zs@virginia.edu</a>><br>
<b>Cc:</b> <a href="mailto:Sbs_gems@jlab.org" target="_blank">Sbs_gems@jlab.org</a> <<a href="mailto:Sbs_gems@jlab.org" target="_blank">Sbs_gems@jlab.org</a>>; Arun Tadepalli <<a href="mailto:arunts@jlab.org" target="_blank">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>
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<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>
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<blockquote type="cite">On Feb 6, 2022, at 9:52 AM, Anuruddha Rathnayake <<a href="mailto:adr4zs@virginia.edu" target="_blank">adr4zs@virginia.edu</a>> wrote:<br>
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<div dir="ltr">Dear All,<br>
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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>
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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" target="_blank">https://logbooks.jlab.org/entry/3932489</a><br>
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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>
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Best,<br>
Anu<br>
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