[BTeam] B-Team meeting, Tuesday @ 1:30pm in MCC Conference Room

[Brian Freeman]

All,


I think it is important to note the events of the weekend and keep them in perspective.  This was not just another 6 shifts dedicated to Hall B tuning.


Wien flip was Thursday Day, Injector recovery followed on Swing. We did the harp scans to characterize the differences throughout the machine.  We recovered to Hall B and Hall A on Friday Owl. Hall A and B beam sizes were different and adjusted accordingly. The Beam was sent to the Hall B Faraday Cup Day Shift Saturday. The beam popped up right away on the Faraday Cup Viewer, no trouble.  Hall B reported only slight adjustments to the beam profile as seen by the 2H02 harp.


This is when the Injector Group was called in to adjust the Position Asymmetry and Compton rates for the Hall A Beam. Changes were put in reducing the size of the chopper circle. During this no beam to Hall B.


Upon sending back through the machine, the timing (visible in an offset to PL though the machine) was way off. This makes sense because of the TOF change through the chopper. When we sent beam back to Hall B a large tail was observed. Likely because of less than optimal bunch length. We then spent a few shifts coming up with a solution that optimized the transport of the tail and Tagger spot size on the 2C24 harp and viewer.  The hall finally accepted to retry the FCup transport even though the beam is smaller than what the hall been requesting the day before. The tail certainly transports down the line to the FCup as seen by the 2H02 Harp, but is in the horizontal plan that they are not as concerned with.


Also, it came to my attention yesterday that every time a Wien angle change has happened the 0L region quads have changed. How were these values determined? If they are changed every time, then we should do the INJ-> NL match each time.


So things up for discussion:

  1.  Do we need to change the 0L quads? It would be interesting to put them back to values saved before the flip on Thursday, then simply take harp scans so see the difference that just the wien angle change made, independent of the 0L quad changes. Perhaps the Inj Group already has a handle on this?
  2.  If we find then answer to the previous question is Yes, then what is the best course of action. Every time we have been able to eventually find a solution in the Hall lines. I think we should do the INJ->NL match measurement  at the very least. We should go through the same process of characterization through the machine (take harp swipes before an after maybe some key viewer shots, like at 0L, 0R, and 1L02)
  3.  Is reducing the chopper circle best practice? Are we going to return it to nominal settings at next wien flip? If we do keep these settings, we should optimize the bunch length. I could do another quick measurement at the Arc 1 SLM???
  4.  As far as Hall B tuning, there is a little bit of a human factor in that not everyone sitting in the Hall B counting house is willing to "try" a certain beam size as measured by the 2C24 harp, to the FCup. We in the MCC and the Counting House should have some guidance on the minimum beam size that we should try, if this guidance is clear we should have our Crew Chiefs push the issue, or call the Hall B Run Coordinator.
  5.  We also need to ensure that the beam is at the correct place at the 2C21 and 2C24 bpms before Degaussing the Tagger. Once the Tagger is degaussed, Hall B will not allow us to raise Halo Counter FSD set points far enough to get beam to the end of the line w/o tripping the counters.  We have lost hours to this, and some have been able to simply steer the bleed though from the Hall A beam and using the Halo counters for guidance on left, right, up, or down. Many times though we end up Ramping the Tagger to find the beam again.


Sorry, for the Tiefenbook (No offense Mr. Tiefenback) on this.... Daniel can you think of anything else?

Cheers and see you at 1:30,

-Brian





________________________________
From: BTeam <bteam-bounces at jlab.org> on behalf of Paul Vasilauskis <vasilaus at jlab.org>
Sent: Monday, August 26, 2019 12:31 PM
To: Joe Grames <grames at jlab.org>; bteam at jlab.org <bteam at jlab.org>
Cc: Camille Ginsburg <ginsburg at jlab.org>
Subject: Re: [BTeam] B-Team meeting, Tuesday @ 1:30pm in MCC Conference Room


Yes, we need to review the past issues we've had after a wein change and develop a plan to be followed.

Brian and Daniel were discussing this this morning and should be invited to attend (I know Brian is going to attend, Daniel is Crew Chief but if it is quiet he should be able to attend)

There was mention that Injector match data was taken in the past but a match hasn't been applied since July. After the next wein change do we want to match the Injector to the NL?

________________________________
From: BTeam <bteam-bounces at jlab.org> on behalf of Joe Grames <grames at jlab.org>
Sent: Monday, August 26, 2019 9:56:51 AM
To: bteam at jlab.org <bteam at jlab.org>
Cc: Camille Ginsburg <ginsburg at jlab.org>
Subject: [BTeam] B-Team meeting, Tuesday @ 1:30pm in MCC Conference Room


Dear B-Team,


Yves is on travel, I'll stand in for him at tomorrow's meeting.


So far, the agenda includes:

  1.  Brief contextual remarks on injector spin reversal: past, present and future
  2.  Diagnosis and understanding of the recent tuning events to restore Hall B beam (i.e. our summer experiences)
  3.  Does manipulating the Hall B ramp become a standard procedure for tuning now?
  4.  What else...?

Please send me your contributions to the meeting and come prepared with any beam studies that may be critical to do schedule before the SAD begins Sep 9.

Best,
Joe

PS - Can someone show me how to edit the BTeam twiki, otherwise I'll plan for old-school w/ paper and projector?


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/bteam/attachments/20190827/eb5c98b0/attachment-0002.html>