[BTeam] Thoughts on the energy locks

[Yves Roblin]

The BEM determination for Hall A  is actually more accurate that ARC1/ARC2. The Hall A arc dipole string is cross-calibrated for energy measurement with the reference dipole and there is no correctors in the Hall A arc. So, yes, this would work. It would have to be such that when we do this, ARC2 elock is disabled of course. This lock would use the SL (the same zone that ARC2 elock uses) to regulate the energy.

Of course, with that, you can also dial in whatever energy offset is desired. The one thing we will want to do is make sure the Hall A dipole string is commensurate with the ARC2 string so that when we switch from one to the other we dont move the energy for the other halls.

________________________________
From: BTeam <bteam-bounces at jlab.org> on behalf of Dennis Turner <dturner at jlab.org>
Sent: Monday, August 24, 2020 10:12 AM
To: bteam at jlab.org <bteam at jlab.org>
Cc: Christopher Slominski <cjs at jlab.org>
Subject: [BTeam] Fw: Thoughts on the energy locks

Here's a discussion between me and Chris Slominski about using the existing energy locks to lock beam energy in Hall A rather than FFB or the Arc2 energy lock.  It's yet another option we can explore for energy stability.

Dennis

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From: Chris Slominski <cjs at jlab.org>
Sent: Monday, August 24, 2020 6:33 AM
To: Dennis Turner <dturner at jlab.org>
Subject: Re: Thoughts on the energy locks


Any BEM measured section could be the source of energy error. The three sets of controls, LINACs, would only be able to be used once per measurement section. Are we confident the Hall A energy error estimated by BEM is accurate? This could be done before the end of this run.


On 8/21/2020 10:16 PM, Dennis Turner wrote:
Hi Chris,

  There was some discussion earlier today about the recent energy drifts in Hall A.  They would normally use either the 2A energy lock or Fast Feedback to lock the beam energy in the hall, but FFB has been exhibiting other undesirable effects, and Arc 2 only has nA beam until Hall C comes back on line.  Would it be possible to use the existing arc energy locks to lock the energy in a hall?  The existing arc energy locks look at the BEM signals for the arcs, like ARC1:p and ARC2:p.   It seems to me that it wouldn't be terribly difficult to have additional energy locks for the halls that look at the hall BEM readbacks, like HALLA:p for example.  I could imagine some logic that would, for example, exclude using the 2A and a hall to lock energy at the same time.  What are your thoughts on this?

Dennis
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