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Hi Sean</div>
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Thanks for letting us know.</div>
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Yes, it would be OK to get 20 uA on LH2. Please make sure to set the current limits accordingly.</div>
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Later, for GEP-5 we will have to go to much higher currents, of the order of 70 uA; so going to 20 uA now would be a good data point for us.</div>
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As Kondo has suggested before, while you are getting this current, please monitor the GEM current, if it is not stable and keep going up (after the initial increase following the beam current change), you my want to turn the chambers off</div>
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Best</div>
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Nilanga</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Sbs_gems <sbs_gems-bounces@jlab.org> on behalf of Sean Jeffas <sj9ry@virginia.edu><br>
<b>Sent:</b> Monday, November 15, 2021 11:01 AM<br>
<b>To:</b> sbs_gems@jlab.org <sbs_gems@jlab.org><br>
<b>Subject:</b> [Sbs_gems] [EXTERNAL] Chance for GEM study at 20 uA?</font>
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<div dir="ltr">Hi Kondo, Nilanga, and Evaristo,
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<div>The MCC is investigating some RF beam issues today, and they said that they will send 20 uA of beam to hall A while doing their study. The question is, can we keep the GEMs on to see the current draws at 20 uA? We would try it on LH2, which has already
been tested up to 10 uA. Here are the numbers for currents at LH2 that we have taken so far:</div>
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<div>No beam: <a href="https://logbooks.jlab.org/entry/3943588">https://logbooks.jlab.org/entry/3943588</a></div>
<div>8 uA on LH2: <a href="https://logbooks.jlab.org/entry/3943079">https://logbooks.jlab.org/entry/3943079</a></div>
<div>10 uA on LD2: Sadly no screenshots were taken, so I will quote the EPICS values</div>
<div>UV Layer 0: 812 uA INFN J0 bot: 116 </div>
<div>UV Layer 2: 804 uA INFN J0 mid: 118</div>
<div>UVa XY 0: 743 uA INFN J0 top: 112</div>
<div>UVa XY 1: 768 uA INFN J2 bot: 113</div>
<div>UVa XY 2: 769 INFN J2 mid: 113</div>
<div>UVa XY 3: 771 INFN J2 top: 0 (off)</div>
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<div>So if we go up to 20 uA on LH2 I assume we double the excess currents found here we would certainly pass the trip limits on all modules on the front tracker. This For example UV layer 0 will go up to probably 870 uA. Would this be safe? Are you guys ok
with this test?</div>
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<div>Best,</div>
<div>Sean</div>
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