[Sbs_gems] [EXTERNAL] Chance for GEM study at 20 uA?

[Liyanage, Nilanga K (nl8n)]

Hi Sean

Thanks for letting us know.

Yes, it would be OK to get 20 uA on LH2. Please make sure to set the current limits accordingly.

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.

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

Best

Nilanga
________________________________
From: Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of Sean Jeffas <sj9ry at virginia.edu>
Sent: Monday, November 15, 2021 11:01 AM
To: sbs_gems at jlab.org <sbs_gems at jlab.org>
Subject: [Sbs_gems] [EXTERNAL] Chance for GEM study at 20 uA?

Hi Kondo, Nilanga, and Evaristo,

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:

No beam: https://logbooks.jlab.org/entry/3943588
8 uA on LH2: https://logbooks.jlab.org/entry/3943079
10 uA on LD2: Sadly no screenshots were taken, so I will quote the EPICS values
UV Layer 0: 812 uA        INFN J0 bot: 116
UV Layer 2: 804 uA        INFN J0 mid: 118
UVa XY 0: 743 uA           INFN J0 top: 112
UVa XY 1: 768 uA           INFN J2 bot: 113
UVa XY 2: 769                INFN J2 mid: 113
UVa XY 3: 771                INFN J2 top: 0 (off)


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?

Best,
Sean
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