[Sbs] [Revised Logentry] RC Daily Summary - 10/01/23

[ojevons at jlab.org]

Logentry Text:
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And beam is back in Hall A!

Technically, beam was first delivered onto the polarized cell at 12:50 during yesterday's Day shift, but it only lasted for 30 minutes before the machine tripped. This was the end of beam-on-target until 11pm, when MCC were finally able to bring back 35uA onto the He3 cell. I asked the Owl crew to call me if the beam was stable for 2 1-hour runs in a row, but because this was judged not to have happened, the beam was kept at 35 uA. Day shift today kept taking data at 35uA until 1:30 pm, when we were able to increase the current to 40uA. Since then, the beam has been a bit choppy, but we will keep our eye on things and see if the situation improves.

On the detector side of things, hodoscope channel 48R has joined its neighbour with an issue in the crate - it's setpoint voltage has been put at 0V, and we await an opportunity to get into the hall to investigate (https://logbooks.jlab.org/entry/4190078). In addition, there were connection issues with DAQ crates ROC 22 and ROC 23 - these seem not to have become a problem since changing the CODA configuration from 3-stream to NoSBSGEMs.

And onto the big thing from earlier today. Overnight, data had been taken with, as it turns out, the wrong BBCAL high voltage settings. These were last set during Swing shift on the 28th, to the relevant settings for when both the BB and SBS magnets are off. Since then, and with the push to get beam back into the hall, I had completely forgotten that these needed to be changed back. That means that all runs between 5437 and 5460 inclusive are using the incorrect settings - they might still be able to be used, but will need extra work to calibrate. This issue was fixed with assistance from Kate, and now we are running as we should be.

These runs with bad HV settings contain 0.696C of raw charge (0.569C of polarization-corrected charge). Since then, 0.435C of uncorrected charge (0.346C corrected) has been collected.

The latest NMR has the target polarization at 39.9% (https://logbooks.jlab.org/entry/4190555).

The current plan is to run at 40uA for a few hours, then investigate the possibility of increasing to 45uA. Should 45uA prove to be too unstable for efficient running, then shift crews can return to 40uA as needed.

We will resume the RC meeting on Monday at 3:30 pm.


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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/4190591
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