[Hallc_running] [New Logentry] Status Update

[pooser at jlab.org]

Logentry Text:
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Yesterday began with the SHMS at -1.6 GeV and 39 degrees while the HMS was at -1.35 GeV and 59 degrees.  At ~3:40 we completed collecting data at the aforementioned HMS kinematics point and the momentum was reduced to -1.18 GeV (https://logbooks.jlab.org/entry/3540913).  There were numerous LN2 level alarms in the SHMS which encountered during the day and swing shifts  (https://logbooks.jlab.org/entry/3540880).

55 uA beam was delivered until ~9:30 pm as a result of instabilities in the machine. A further drop in current to 40 uA occurred at ~11 pm which is where we ran for the reminder of the owl shift (https://logbooks.jlab.org/entry/3541379).  At ~1 am the SHMS was rotated to 33 degrees and the momentum was increased to -3.2 GeV/c (https://logbooks.jlab.org/entry/3541190).  Production data was collected with 40 uA on target with ratty beam (~15 trips/hr) throughout owl shift.  The trips are related to RF issues with the C25 and C50 cavities.

At ~8 am this morning the arc 8 magnet tripped off and beam went away.  This morning’s trip was identical to the magnet over temperature alarm that caused a ~1 hr period of down time Wednesday evening (https://logbooks.jlab.org/entry/3540504).  At first it was hypothesized that the issue could be resolved in the absence of an access.  However, as more information became available from the DC power group, it was learned that the magnet had to be acid flushed in order to recover the magnet.  This procedure required an access which will take an estimated 4-6 hrs.

The hall was surveyed at 9:30 am and placed in controlled access at 10 am at which point multiple groups conducted work in the hall and is discussed below.  When beam comes back we will continue collecting production data according to the current F2 run plan.

Work completed in the hall this morning:
Andy Kenyon: replaced the relays on the cold return valve 13 on HMS Q1
Tony Delacruz: swapped out the CW dump viewer camera
Mark Jones:  took a photo of the super-harp girder
Steve Lassiter: inspected HMS Q2 power supply and everything is good to go
Kieth Cole et.al.: big BPM both upstairs and in the hall

Special notices in effect for shift crews:
Recovering the HMS DAQ: https://hallcweb.jlab.org/wiki/index.php/Hall-C_HMS_DAQ_Failure_Modes
Trouble shooting HMS Q2 power supply: https://logbooks.jlab.org/entry/3537306
TO Instructions for LH2 <--> LD2 switches : https://logbooks.jlab.org/entry/3534487

We will meet today in 200C at 1:30 pm (second floor of the counting house)
Link: https://bluejeans.com/543903672
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2) Enter Meeting ID: 543 903 672
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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/3541438
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