[FFA_CEBAF_Collab] [EXTERNAL] Fw: Alternative FFA Arc - A tech note describing a brainstorm

[Brooks, Stephen]

________________________________________
From: Brooks, Stephen <sbrooks at bnl.gov>
Sent: 07 December 2023 11:45
To: Ryan Bodenstein
Subject: Re: [FFA_CEBAF_Collab] Alternative FFA Arc - A tech note describing a  brainstorm

The thing about that idea is that you actually need an FFA cell for each region of the arc where the average dispersion is slowly varying (and going through zero and changing sign!)

The average dispersion through the cell for simple F-D- lattices is roughly proportional to (cell length)^2 times curvature.  This presents some problems if you want it to go to zero.

"Inside out" FFA cells where the dispersion is negative: high-energy orbits on the inside, exist but I think they're usually sub-optimal from a magnetic field point of view.  The main bend wants to send the high energy orbits to the outside, so if you want them on the inside, you have to add a lot of quadrupole that isn't contributing directly to the bending, thus poorer efficiency.

    -Stephen

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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 December 2023 11:34
To: ffa_cebaf_collab at jlab.org
Subject: [FFA_CEBAF_Collab] Alternative FFA Arc - A tech note describing a      brainstorm

Dear FFA Colleagues,

Since we’ve been entertaining a lot of alternative options lately, I thought I’d add to the pile.

I’ve spoken to a few of you about this, but I thought I’d write it down informally and share it with the group. Please note: this is no more than brainstorming put to paper (or digital paper, if you will). But it describes a few alternative ways to design the FFA arcs. These ideas may or may not be feasible, and may or may not help things. They will likely cost more, but may be worth it.

Attached, you’ll find a copy of the tech note. If you are on JLab’s network, you can also find it here:  https://jlabdoc.jlab.org/docushare/dsweb/View/Collection-55373

Cheers!
Ryan

Dr. Ryan Bodenstein (he/him)
Staff Scientist II – Center for Advanced Study of Accelerators (CASA)
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