[Bteam] no joy again: delivering high current, parity quality beam to Hall C

[Todd Satogata]

The Hall C Qweak beam problem continues even after spending 12h today on
injector configuration checks, 5s polling removal, and retuning with the
PREx configuration from August. After work by Reza, Alicia, and Mike
Spata, we were able to transport 165 uA to the injector dump, but were
only able to transport 80-90 uA to Hall C. About an hour later these
numbers were down to about 50-60 uA to the injector dump and 20-30 uA
to Hall C, with trips in both the injector chicane and hall transport.

This means that the "changing the configuration" card did not help, and we
should be prepared tomorrow to take the next step, moving forward (or
rather reverting) to the 130 kV gun voltage. It's important that we do
whatever we can to put ourselves in the position of beam delivery to
both halls over the upcoming weekend. We'll have another meeting tomorrow
morning after the 8 AM to review further alternatives and review
comparisons of injector viewers taken several times during the day on
Wednesday.

Some items of note:
   - 5-pass pathlength looks reasonable
   - Fopt out of the injector looks to have some vertical steps later
     into the arcs, but injector match into NL looks okay
   - Viewer profiles in Hall C have basically the same aspect ratios
     as design, but harp scans show beam sizes 150% larger than "good"
     values seen before.
   - Prebuncher voltage/phase were reliable enough that Joe got good
     prebuncher voltage calibration data earlier in the day, so
     the prebuncher is likely stable.

                                                 -Todd

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Todd Satogata | CASA Group, Jefferson Lab | (757) 269-6281 | satogata at jlab.org
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