[FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, Jan. 26

Fri Jan 26 16:19:25 EST 2024

Excellent!

From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Meot, Francois via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Date: Friday, January 26, 2024 at 4:09 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>, Ryan Bodenstein <ryanmb at jlab.org>
Cc: Planche Thomas <tplanche at triumf.ca>
Subject: [FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, Jan. 26

Alex, and All,

Regarding the highlighted comment in the minutes:
[cid:9f0a7d51-30e2-4a13-a414-9bbb6220192a]
and, following that:

"Oliver was making the point about transmission. Not aware if the explanation has been written down and presented. He’d like to know if it’s written down."

A possible explanation has been written down, yes:

A possible cause for the bad beam transmission is explained in my speech at  May 25, 26, 2022's CBETA advisory committee. My slides are attached here.

Namely: A 180deg y-rotation of a combiner dipole is enough to  jeopardize the optics (this is  shown in slide 4) and thus beam transmission. The on-line model was using matrix transport but the problem cannot be seen with matrix transport, it requires using field maps (that's my comment in slide 2).  If one is using field maps,  showing the problem is easy:  just a matter of flipping the field map, in an equivalent way to y-rotating the dipole magnet by pi.  The  strong change in the optics this causes comes from the fact that the end chamfers in the dipole have been designed  (for some reason) not symmetric with respect to the vertical plane (s,y). At the time, I asked to take a look at the dipole in cause in the recombiner, but I was told it was not possible to see the chamfers from outside, too much packed, no room left to sneak an eye.

Beyond that issue in that "conventional" style of beam line, in a general manner, we do know since KEK FFAG developments started in the 1990s that it is indispensable to model FFAG lattices using magnet field maps.  Well... if we don't, then it is still time to learn 🙂   Our MURA colleagues 70 years ago were already using field maps and Runge-Kutta integration of Lorentz force to design their machines, and they succeeded making those three electron rings work  -  ~10,000 passes acceleration, and they might as well have subsequently decelerated to injection energy as succesfully ... may be they did!  Same at KEK and KURRI with the proton rings, design and operation based on OPERA field maps. Same with RACCAM prototype spiral FFAG dipole and the fine lattice optics which  its OPERA as well as its measured field maps resulted in.  This  was just deemed useless for CBETA operation ...

In passing, we also know that a radial dependence of dipole gap height causes a radial dependence of the flutter (a substantial dependence, as Thomas used just that property to make the cyclotron isochronous - 85 years ago). An additional reason to work with field maps when dealing with FFAG lattices based on offset quadrupoles, just what we did in EMMA 20 years ago.

Anyway,  back to the JLAAC's point above, the question is still pending and might contribute answering Oliver:  is  (any) CBETA recombiner dipole y-rotated by pi? and, an ancillary question,  was for that reason its (their) actual optics missed  in CBETA  on-line model?

François

François Méot
Brookhaven National Laboratory
Collider-Accelerator Department
--
Adjunct Professor
Dpt of Physics & Astronomy
Stony Brook University - SUNY
________________________________
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: Friday, January 26, 2024 12:11 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Cc: Planche Thomas <tplanche at triumf.ca>
Subject: Re: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, Jan. 26

Dear Colleagues,

That was quite an active meeting! Attached (and uploaded) you’ll find our minutes.

Everyone have a great weekend.

Cheers!

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, January 22, 2024 at 7:25 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Cc: Planche Thomas <tplanche at triumf.ca>
Subject: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, Jan. 26

Dear Colleagues,

We will continue our design efforts this Friday, Jan. 26, at 11:00 am.

* Recent JLAAC  recommendations and upcoming FOA opportunities - Alex Bogacz

* Extending FFA energy acceptance with sextuple component - Stephen, Dejan

* 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

12000 Jefferson Avenue,

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=RknuJfeoWO7gRVvXGFZfehrqFTCxAQ2zsxYPw5Su7BGyqlHq41xUMrNHmAWrIqcM&s=z0yavlWaO4M-tvwBAWkm6LThYA16wVMNeiRYy-64_jM&e= <https://urldefense.com/v3/__https:/jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!CRRrPkMxAZEEUkRVyQcc8dIt0sqnCHVPdrMIgnV2UXprPjplBPjAI3FycgJvfVgMfVwKgdB2ggm7uZFZUzgub5uboA$>

In case of problems, the zoom room is below:

Meeting ID: 161 489 8082

Passcode: 123456

________________________
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