[FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, May 30

Mon Jun 2 14:18:18 EDT 2025

The factor doesn't need to be exactly 1/sqrt(2)=0.7071... either, you can adjust it slightly so that the available energies that (12GeV) CEBAF can produce in that location have a similar range of tunes to the full-energy FFA arc cell.

In particular, a larger-than-expected beta function probably means one of the tunes has got closer to zero than intended.  Might be a higher order effect.

The graph of the field on orbit shows that the six offset segments of the first magnet are working correctly.  Notice how the peak of the largest field magnitude is kept flat by the segments.  There's probably an orbit on the other extreme where the other magnet reaches its max field and that will hopefully have the segments flattening the peak similarly.  Without the segmentation, the fields on orbit would be ~parabolic longitudinally through the magnet, meaning some parts of the orbit requiring stronger field than others (or equivalently, the orbit is going to different transverse locations in the aperture).  The magnet design prefers that MAX field is reduced, even when average field stays the same.  So essentially the segmentation follows the "hardest" (max field) orbit in any given magnet.

     -Stephen

________________________________________
From: Salim Ogur <ogur at jlab.org>
Sent: 02 June 2025 13:54
To: Brooks, Stephen; Alex Bogacz via FFA_CEBAF_Collab; Berg, J Scott
Subject: RE: [FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, May 30

Dear Stephen,

I have just implemented the sqrt length and sqrt of the bending angles of the old "baseline" FFA FODO lattice on Bmad model. The results are promising as Stephen foresees, see attached. The beta function for 11 GeV looks like scaled up rather than down, but the lower energies return ~10 m or lower beta funcs.

I think as Kristen has taken the initiative, many thanks again, for correcting the baseline lattice in the orbit positions; on the other hand those new scaled FFA lattice would suffice the LDRD full proposal onto the beam transport testbed that we would submit if we are given green light.

Thanks and regards,
Salim.

-----Original Message-----
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> On Behalf Of Brooks, Stephen via FFA_CEBAF_Collab
Sent: Friday, May 30, 2025 1:20 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>; Berg, J Scott <jsberg at bnl.gov>
Subject: Re: [FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, May 30

Yes, I thought maybe we could overall shorten the cell and that would naturally decrease the energy range, even the overall radius of curvature and magnet cross-sections and fields could be the same.  The betas would scale down with lengths.  Tunes would be the same.

I think it's basically to get 1/2 energy you multiply all lengths (and bend angles) by 1/sqrt(2).  11-22GeV would become 5.5-11GeV.

Scott, I can go through what the "baseline" FODO lattice I provided way back in Dec 2022 is, the following file shows one arc element-by-element.

https://urldefense.proofpoint.com/v2/url?u=https-3A__jeffersonlab-2Dmy.sharepoint.com_-3At-3A_r_personal_tristan-5Fjlab-5Forg_Documents_Grad-2520Student-25202019_Graduate-2520Student-2520Steering_CEBAF-2520FFA-2520Working-2520Group_Optics_FFA-2520Arcs_Brooks-5F20221216_Muon1_listcomponents-5FCEBAF-5FDec-252722-5Feast-5FMatchBentTrue.txt-3Fcsf-3D1-26web-3D1-26e-3DaxqOuR&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=Ogg4WFNBwvADBq3fkmCLiJ7SaRDPYtawHzJElJMB0jE&m=PopKNslxSMCtM51-QDazXpIquCL-gDw1DUDZucbo6gUuKWInMm7nJOYM25nmzd7i&s=nNKP_OKUMkAWZcQFVzq5iYBa1SeReueIA_sfmz03HPM&e=

     -Stephen

________________________________________
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Berg, J Scott via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Sent: 30 May 2025 12:36
To: Alex Bogacz via FFA_CEBAF_Collab
Subject: [FFA_CEBAF_Collab] [EXTERNAL] Re:  FFA at CEBAF WG mtg. this Friday, May 30

A couple more thoughts on the discussion we had:

  *
What about putting the cell on a mover that lets us change x-z, to help with setting up different initial conditions?
  *
I'm mildly concerned with a design where we can only probe one side of the aperture, and close to the limit. There seems to be a lot of risk there (beam is not in the mood to reach the energy, magnets come in with a lower Br than expected, etc.). How about a design where we don't quite imitate our cell, but maybe use the same magnet cross sections, but remove one or two slices from each magnet? We could even see if we could have two options, one where we remove the end slices, and one where we have all the slices. I'm being sloppy on details here, so maybe it's not as straightforward as I'm imagining, but it seems something like this could be made to work.

-Scott

________________________________
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Donish Khan via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Sent: Friday, May 30, 2025 12:17
To: Alex Bogacz <bogacz at jlab.org>
Cc: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>; Sadiq Saitiniyazi <saitiniy at jlab.org>
Subject: Re: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, May 30

Hi All,

Great discussion today. Attached are the meeting notes (FFA_at_CEBAF_Minutes_20250530.pdf<https://urldefense.com/v3/__https://jeffersonlab-my.sharepoint.com/:b:/r/personal/tristan_jlab_org/Documents/Grad*20Student*202019/Graduate*20Student*20Steering/CEBAF*20FFA*20Working*20Group/Minutes/FFA_at_CEBAF_Minutes_20250530.pdf?csf=1&web=1&e=5tBLcc__;JSUlJSUlJQ!!P4SdNyxKAPE!Hth8QVRfyn3UHMdYpmsUIuQaHu7wl7enJtqrepyyyPNres8ltwkhDBquAHIBTrSS8cL07zX9yEwDBFKmHyDGs-zE5g$  >).

Have a great weekend,
Donish

On May 27, 2025, at 3:08 PM, Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org> wrote:

Dear Colleagues,

We will continue our design efforts this Friday, May 30, at 11:00 am.

  *   Gearing up for FFA beam transport test - Salim
  *   Splitter design, magnet error tolerances  - Donish
  *   AOB - ALL

Please, follow a ZOOM invitation below.

Cheers,

Alex

 ___________________________________

S. Alex Bogacz,

Accelerator Physics Group Leader

Center for Advanced Studies of Accelerators

Jefferson Lab

ZOOM connection:

The link is here: https://urldefense.proofpoint.com/v2/url?u=https-3A__jlab-2Dorg.zoomgov.com_j_1614898082-3Fpwd-3DTnUzMS81M2sxbDZIbERJU01tYkJCQT09&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=Ogg4WFNBwvADBq3fkmCLiJ7SaRDPYtawHzJElJMB0jE&m=PopKNslxSMCtM51-QDazXpIquCL-gDw1DUDZucbo6gUuKWInMm7nJOYM25nmzd7i&s=Tf_NdqNNR5CyIz3pJDW6plxtGG31LmavXr7YNfaAX38&e=  <https://urldefense.com/v3/__https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!Hth8QVRfyn3UHMdYpmsUIuQaHu7wl7enJtqrepyyyPNres8ltwkhDBquAHIBTrSS8cL07zX9yEwDBFKmHyB_wsNsYg$  >

In case of problems, the zoom room is below:

Meeting ID: 161 489 8082

Passcode: 123456

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