[Sbs_gems] [EXTERNAL] BB GEM Efficiency Results

[Sean Jeffas]

Hello All,

We have completed the BB HV efficiency scans. See full results here,
https://logbooks.jlab.org/entry/4055432. As listed our HV settings will be:

UV Layer 0 - 3650 V
UV Layer 1 - 3600 V
UV Layer 2 - 3600 V
UV Layer 3 - 3600 V
XY Mod 4 - 3600 V
XY Mod 5 - 3650 V
XY Mod 6 - 3650 V
XY Mod 7 - 3600 V

These numbers have been chosen as the beginning of the efficiency plateau.
They all produce above 86% efficiency Please feel free to respond if you
look at the graphs and think they should be different. Generally we are
comfortable with all the GEMs operating up to 3650 V, so we can reasonably
increase some of them.

Efficiency plateaued a bit earlier than I expected. For example UV layer 2
was used in GMn and we found it was 84% efficient at 3600 V, meanwhile for
this run we found it is 92% efficient at the same voltage. I wonder if the
new CM calculations are causing this improvement. Regardless we will run
like this for now, and increase the voltage if there are any issues when we
start taking production data.

Best,
Sean
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