[Sbs_gems] [EXTERNAL] BB XY Layer Module 5 Low Efficiency

[Sean Jeffas]

Hi All,

As I have been showing at the meetings, one module on the BB XY layer has
suddenly decreased in efficiency since GMn ended without anyone physically
touching it. See my most recent update at the link below.

https://sbs.jlab.org/DocDB/0002/000293/003/BB_XY_Layer_Issue_8_31_22.pdf

Right now our best guess is that something inside the GEM may be blocking
the flow. We tried turning up the flow but saw negligible improvements and
it is risky to keep increasing the flow. We also may want to turn up the
flow high for several days with no HV on to try to flush things out. With
the HV increased to 3742 V the efficiency is only ~8% lower than the other
GEM modules. I believe this will be sufficient to run with during GEn and
it is not critical to replace this module, given how difficult and risky
that would be.

Best,
Sean
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