[FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, April 4

Fri Apr 4 13:05:51 EDT 2025

Yes, though there’s no reason to use SVD. The right way is to use a transposed QR decomposition, which I’ll refer to as a PLQ decomposition. The P is a permutation matrix which we’ll ignore for these purposes, it’s just to help with numerics. The idea is that you have

[L 0][Q1 Q2]^T x =  b

The columns of Q2 define the space that locally leaves the match in place. QR is direct whereas SVD is iterative, and thus is generally preferable, and SVD intrinsically assumes that orthogonality (i.e., symmetry under rotations) somehow makes sense in both spaces, which it really doesn’t in the beta function match space.

-Scott

From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> On Behalf Of Nick Sereno via FFA_CEBAF_Collab
Sent: Friday, April 4, 2025 12:24 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>; Ryan Bodenstein <ryanmb at jlab.org>; Brooks, Stephen <sbrooks at bnl.gov>
Subject: Re: [FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, April 4

Hi Scott,

You said something interesting during the meeting I did not quite hear as the audio was going in and out at my end.

I think you said to Donish that to understand how to keep the twiss/dispersion parameters constant while trying to
set the R56 to what  one wants.  You described to consider the matrix equation:

Dx = b

where x is the vector of quad strengths, b is the vector of beta functions/dispersion and you want to find the linear combinations
of quad strengths that don't change the vector b.  I think you are searching for the null space of D (the matrix of derivatives) which
can be found using SVD of the matrix D assumed to not be of full rank.   Anyway, that was my interpretation of what I partially heard
you say but I think you used a different algorithm to obtain the null space.

Is this the correct interpretation of what you said?

Thanks,
Nick
________________________________
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org<mailto:ffa_cebaf_collab-bounces at jlab.org>> on behalf of Brooks, Stephen via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Sent: Friday, April 4, 2025 12:09 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>; Ryan Bodenstein <ryanmb at jlab.org<mailto:ryanmb at jlab.org>>
Subject: [FFA_CEBAF_Collab] [EXTERNAL] Re: FFA at CEBAF WG mtg. this Friday, April 4

Sorry I was in a project review for a different FFA(!)

     -Stephen

________________________________________
From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org<mailto:ffa_cebaf_collab-bounces at jlab.org>> on behalf of Ryan Bodenstein via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Sent: 04 April 2025 12:08
To: Alex Bogacz via FFA_CEBAF_Collab
Subject: Re: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, April 4

Dear Colleagues,

Thanks for the good discussion!

Attached are the minutes.

Cheers!
Ryan

From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org<mailto:ffa_cebaf_collab-bounces at jlab.org>> on behalf of Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Date: Monday, March 31, 2025 at 5:54 PM
To: Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Subject: [FFA_CEBAF_Collab] FFA at CEBAF WG mtg. this Friday, April 4

Dear Colleagues,
We will continue our design efforts this Friday, April 4, 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=te-lLg-vSoDwMBjseLUaw3xcu5jYz_Ny2M_wPF-XRVjsU8ew333N0xZUJYc3Tyxf&s=YoiFqr2WlLAR-C_sjdSO0tKTuWhfq-X7S3CyO19BDuc&e= <https://urldefense.com/v3/__https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!Gg4oWbBxGQSSg8iwfieUq9U3j7MLZUDVF3-z6-GshsiVO1GzyT-yu_oHm98C03qrmvDK_S9hywyxdaOgEjjrXV0hnro$  <https://urldefense.com/v3/__https:/jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!Gg4oWbBxGQSSg8iwfieUq9U3j7MLZUDVF3-z6-GshsiVO1GzyT-yu_oHm98C03qrmvDK_S9hywyxdaOgEjjrXV0hnro$%20 > >

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

_______________________________________________
FFA_CEBAF_Collab mailing list
FFA_CEBAF_Collab at jlab.org<mailto:FFA_CEBAF_Collab at jlab.org>
https://mailman.jlab.org/mailman/listinfo/ffa_cebaf_collab 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/ffa_cebaf_collab/attachments/20250404/b0bc21c1/attachment-0001.html>