[Halla_running] [New Logentry] Status update

[sanghwa at jlab.org]

Logentry Text:
--
Beam was restored during the swing shift yesterday and we restarted production running around 8pm. 

We took controlled access when the machine was down during the day. Bogdan went down to the hall and check the LHRS VDC noise issue. No obvious clue related to a hardware problem was found, v2 plane still has the noise. Discussion among the experts continues, and Chandan and Devi have been monitoring it with the pulser trigger (many thanks!).

Beam quality during the owl was not great, high trip rates from BLMs and Moller ion chamber rate spikes. The trip rate from the ion chamber was reduced after MCC adjusted the orbit in the machine. 
The fast current ramping sometimes overshot the max juice limit (currently set to 155uA) and caused trips, so the operator had to manually bring us to ~130uA first and then to 150uA for some time after trips. MCC suggested to lower the ramp rate for now as we have high trip rate in general, and we agreed. If we go to more stable operation, we may consider to revert this change back. We also changed the initial attenuator setting for beam recovery after a trip from 2uA to 50uA. Silviu confirmed this doesn't cause any issue for our target. This means overall the recover time to 150uA will be similar after a trip.

Stabilizing the beam by engaging FFB (with RF) for a short time didn't go well as we wanted over night. Our crew diligently monitored the parameters and logged them. 
This morning MCC suggested to improve dpp by adjusting the energy using SL20 energy vernier, and that seems to work better given the struggle we had with FFB last night. 

Overall we have <40% good events from the online cuts for the runs taken during the owl. We are running in much stable condition now, we will continue monitor the data and taking production.

There will be no 3:30 meeting this weekend.

---

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/3832422
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halla_running/attachments/20200822/92f59701/attachment.html>