[Sbs_gems] Suggestion: run LH2 at 10-12 uA instead of 15 uA

[Andrew Puckett]

Hello all,

In light of our new reality of the apparent hardware failure of 2/3 of J0 modules, we are back to basically having only 4 good tracking layers in BigBite. Moreover, in light of the fact that we see a significantly more severe gain/efficiency drop in all the GEMs (except, perhaps, the back tracker) on LH2 at 15 uA than on LD2 at 8 uA, and in light of the fact that the LH2 running is mainly for calibration purposes, I would like to suggest that we back off in beam current for the LH2 running unless and until we can get a fifth good layer into BigBite again. Moreover, in light of this failure of J0 I would advocate that we stick to being a little bit more conservative in terms of trying to push higher luminosities until the cause and scope of the J0 failure are better understood. I am cc’ing Bogdan and Brian on this message as spokespeople. We can have a discussion of the idea at the RC meeting this afternoon.

Andrew

Andrew Puckett
Associate Professor, Physics Department
University of Connecticut
196 Auditorium Road, Unit 3046
Storrs, CT 06269-3046
Office phone: (860) 486-7137
https://puckett.physics.uconn.edu<https://puckett.physics.uconn.edu/>
puckett at jlab.org<mailto:puckett at jlab.org>
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