[Sbs] [New Logentry] RC Update and plan for swing and owl

[Paul King]

RC Update and plan for swing and owl<https://logbooks.jlab.org/entry/3927026>

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Lognumber 3927026<https://logbooks.jlab.org/entry/3927026>. Submitted by pking<https://logbooks.jlab.org/user/pking> on Sun, 10/17/2021 - 20:21<https://logbooks.jlab.org/entries?start_date=1634512889&end_date=1634520089&book=HALOG>.

Logbooks:       HALOG<https://logbooks.jlab.org/book/halog>

Through the afternoon, we collected several hours of data with 5uA on LH2 with the SBS magnet set in negative polarity at 25% full current.

A little after 17:00, we performed a threshold scan for BBCal with 5uA of beam on LH2 (https://logbooks.jlab.org/entry/3926919).

We then changed the BigBite magnet from 750A to 375A (https://logbooks.jlab.org/entry/3926924), and took run 11284 for 15 minutes. We then restored BigBite to the nominal 750A current ().

We requested the SBS magnet and correctors to be turned off (https://logbooks.jlab.org/entry/3926931 and https://logbooks.jlab.org/entry/3926936), then checked centering on the 2mm hole target (https://logbooks.jlab.org/entry/3926957). We chose to put the lock positions at (-0.8, 0.5) on both BPMs.

We took 30 minutes of LH2 data at 5uA in run 11287.

We have now made a change in the GEM HV settings using the values specified in https://logbooks.jlab.org/entry/3926899, and are taking ~10 minute runs at 1uA beam current increments to monitor the GEM current stabilty and determine occupancies and efficiencies.

Plan for this evening and overnight
==========================
1. Complete the incremental beam current runs to check the GEM performance with the new voltages

2. Take a run with only the coincidence trigger (T3) active. About 20 minutes with 5uA on the LH2 target.

3. Restore prescales to have BBCal only (T1). Take ~1 hr long runs at 5uA on LH2. This would be with SBS off for the whole night (unless the plan changes).

4. We should stop the beam at 05:30 to allow radiation to decay before the survey for hall access.
After we stop the beam, we should ramp BigBite to zero and push "power off". Log that was done.
If we have turned SBS on during the night, you should ask OPS to ramp it down and turn off the power.
The survey is expected to be done to allow the hall to go to restricted access by about 08:00.

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