[FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, March 7

[Brooks, Stephen]

If you want to investigate having "more gradient", try filling the whole line, at least the FFA end, with alternating quad cells with perhaps 10T/m of field.  (How to do this might be my problem i.e. magnets).
This should keep the betas and the dispersions down.
Bulk path length can be done with overall line geometry as you can add dipole to those quads.
Beta matching should be easier as it will require just a tweak to magnet lengths, generating beta phase advance is easier with shorter cells.
The difficult one will be R56, as we now have smaller dispersion.  You want dispersion in dipoles for R56 adjustment, but dispersion in dipoles is exactly what you don't want for I_5 emittance growth!  I suggest trying to solve this by reducing R56 in the FFA cell.  I've already got cells with sextupole like option "C" in the attached spreadsheet that can make R56 about 3x smaller than the baseline.  Dejan has one that does similarly.  Maybe we can flatten the TOF entirely with higher order fields, I'll need to try that later.

As for HOW we make those gradients in crowded spaces, have a look at Figure 5 in my IPAC'21 paper:
https://urldefense.proofpoint.com/v2/url?u=https-3A__accelconf.web.cern.ch_ipac2021_papers_tuxc07.pdf&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=Ogg4WFNBwvADBq3fkmCLiJ7SaRDPYtawHzJElJMB0jE&m=cH7WU-M_-M030-k_S17mRkr75wnVCT0EW6v_YxWQ87S8SVaj7pRPPxmlw4KCKDJv&s=fGqlkxTts30s-Qa_wVTcxPAJqnArLrUiNBFMJfHc4-w&e= 

It's too tiny for our beam pipes, so consider doubling the size:
gradient 50T/m -> 25T/m
bore diameters 20mm -> 40mm
beam separation 30mm -> 60mm
midplane slot full height 12mm -> 24mm

That would fit around some crowded splitter pipes I think?

In the end, I'll prepare a tool to do the 3D optimisation for Halbach cuboids (no iron).  You may want electromagnets for energy tunability, which will also be complicated, but possible in principle.

     -Stephen

________________________________________
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Ryan Bodenstein via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Sent: 07 March 2025 12:39
To: Ryan Bodenstein via FFA_CEBAF_Collab
Subject: Re: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, March 7

Dear Colleagues,

Attached (and uploaded), you’ll find our minutes from today’s meeting.

Have a great weekend!
Ryan

From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Date: Monday, March 3, 2025 at 6:35 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Subject: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, March 7


Dear Colleagues,
We will continue our design efforts this Friday, March  7, at 11:00 am.

  *   Splitter design update - 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=cH7WU-M_-M030-k_S17mRkr75wnVCT0EW6v_YxWQ87S8SVaj7pRPPxmlw4KCKDJv&s=ijdBv8crAldFAkjSX-4kepOd1GAw5Be7qFewetnsKPI&e= <https://urldefense.com/v3/__https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!F5zCpFGgJS3KO_S1sHB3NQfeCP1upRTf7FX7VbSgd2ijtDp9gn3MM_23mVZ6yj0kD07KWnprWuDrbn_qigKUvGGb1d4$>

In case of problems, the zoom room is below:
Meeting ID: 161 489 8082
Passcode: 123456
________________________
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