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    User name puckett

    Log entry time 22:28:54 on January 21, 2009

    Entry number 257189

    This entry is a followup to: 257186

    keyword=Regarding MWDC HV trips...

    Please note that in HALOG 257186, when I wrote "the recommendation of the shift crew" I meant to write "the recommendation of the expert shift (in the back room)".

    The Run Coordinator and the experiment spokespeople may want to consider alternatives to using a low ramp rate to try to prevent trips. I'm not sure it is actually helping. It may just be a coincidence that it appears to help. I suggest trying a slightly lower beam current, e.g. 13.5 uA or 13 uA. Sacrificing 1/14 of the beam current, if it improves the efficiency by more than 1/14, will be worth it.

    Also, note that when I asked MCC to lower the ramp rate back to .25 uA/s, the operator mentioned that he was "bringing us up manually" because using the "lock" (current lock?) would have brought us up much faster. However, he mentioned that the last few trips (both of which had caused the BB WCs to trip) had both been caused by the FSD of the Hall A ion chambers. He also mentioned that bringing up our hall manually could be affecting the quality of our beam orbit.

    A copy of this log entry has been emailed to: xqian@jlab.org, rsubedi@jlab.org