[Sbs_gems] [New Logentry] Plan to increase Argon in SBS GEM gas mix

[hszumila at jlab.org]

Logentry Text:
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After studying the gas system yesterday, we have seen that the read back on the premix cylinder for the SBS GEM gas system is about 77-78% when the cylinder is 75%. This is consistent with how we had set the SBS GEM gas mix for the past year. We are currently sitting at a read back value of 73% assuming that we are at approximately 70/30 gas mix. 

Here is our plan for this morning:
1. We are turning off the SBS GEMs now. 
2. We will increase the SBS GEM gas mix by 2% to get something still less than the 75/25 premix (or 77% readback). This should put us around 73/27 gas mix with a readback of 75% (still less than previously). 
3. We are reducing the GEM HV to 3600V in the SBS GEMs. 

After watching the gas mix ratio change for a bit (toward stability), we will turn on the GEM HV at a reduced beam current to study the ADC distributions and occupancy. We will also compare the read back currents from the previous runs at 3600V at the 70/30 mixture. 

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/4294418
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