[Prex] [New Logentry] RC status update 8/29

[jonesdc at jlab.org]

Logentry Text:
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Following the linac restoration after the CHL crash yesterday, ops tried to reestablish beam to Hall A. Rates in the Compton background region were excessive with only a few microamperes with a few kHz persisting from Hall C bleedthrough even with current off to Hall A. Around 3AM the shift crew called me to ask about pulling out of the chicane and at that time I provided them the guidance not to pull out not wanting at that time to relax efforts to find a solution and fearing that pulling out would be the permanent solution for the weekend. As it turned out, that is, in fact, the solution we will go with. 

After a rather lengthy consultation on the phone between Hall RCs, optics, operations and the PD a long and invasive plan was developed in real time by Yves et. al. (see attached screen shot from Bluejeans) to try to address the issues. It turns out Hall B's backgrounds are so bad likely from halo being transported along with the beam that their data quality is questionable. Hall A's background in the Compton region cannot be addressed without changing the gang phase by 2 degrees which causes troubles for Hall C and limits them to 15 muA, half their desired 30 muA. Javier interjected after about 30 minutes that he believes a long invasive diagnostic program on the weekend is non-optimal and that we should concentrate on beam delivery to C and B with A getting what they can until the pass change. The PD concurred and decided to do only the minimally invasive tests or those that directly impact B. A more permanent solution will be sought after the pass change back on Thursday.!
  Rather than get no beam, we have decided the pull out of the chicane and run straight through for the weekend. 

PD will be meeting with the RCs and optics tomorrow morning at 9AM to reassess the program.

We will not have an RC meeting this afternoon.

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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/3836949
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