The OPAL Discussion Forum

[Adelmann Andreas <andreas.adelmann AT psi.ch>]

Hi Seongyeol

As far as I understand according to your explanation, we can mimic the quadrupole magnet using multipole, but it is not for generating some sort of nonlinear component of the quadrupole magnet (e.g., field nonlinearity at the edge of quad, which is far away from the core).

Well you can add higher order multipole coefficients and get nonlinearities. In case you have measurements you could fit these coefficients. 

I am wondering if my understanding is correct. If so, then I think generating 3D fieldmap might be reasonable for the case I mentioned.

Certainly 3D field maps are a possibility, to my knowledge a Quadrupole can not yet handle  3D field maps.

In addition, I understood about the fringe field of the quadrupole magnet. Either that, or, I think I can use the number of quadrupole component with different strength to mimic the fringe field. 

Yes! 

Cheers Andy 

Thank you very much!

Best regards, Seongyeol

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From: Adelmann Andreas <andreas.adelmann AT psi.ch>
Sent: Saturday, July 8, 2023 03:33
To: Kim, Seongyeol <seongyeol.kim AT anl.gov>
Cc: Piot, Philippe R. G. <ppiot AT anl.gov>; opal AT lists.psi.ch <Opal AT lists.psi.ch>
Subject: Re: Question regarding multipole element and fringe-field of quadrupole magnet

 

Hi Seongyeol good to hear from you!

There is an example in the manual (http://amas.web.psi.ch/opal/Documentation/master/#sec.elements.multipole) that guides you how to mimic a quadrupole with a multiple, check below.

M27: MULTIPOLE, L=1, ELEMEDGE=3.8, KN={0.0,0.11};

QP1: QUADRUPOLE, L=1.20, ELEMEDGE=-0.5265, K1=0.11;

Unfortunately we do not yet have a regression test for this but looking at the implementation I am quite confident that it works :). 

In OPAL-t there are no fringe fields implemented for the multipole element. Maybe you could try to overlap a dipole with zero bending

but the multipole field. In 11.9 there is a general multipole description however to my knowledge this is not yet implemented in OPAL-t.

Cheers A

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Dr. sc. math. Andreas (Andy) Adelmann
Paul Scherrer Institut OHSA/D17 CH-5232 Villigen PSI
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On 7 Jul 2023, at 04:20, Kim, Seongyeol <seongyeol.kim AT anl.gov> wrote:

Hi Andreas,

Hello, this is Seongyeol Kim with the AWA. 

These days, I am performing the OPAL simulations to understand what the emittance growth during the beam propagation along drift-quadrupole beamline, and I would like to ask you some questions about implementing geometric aberration and fringe field of the quadrupole magnet.

• I would like to know how to use the multipole to add nonlinear filed of the quadrupole magnet (to have geometric aberration and to see the phase space distortion). 

• I am wondering if you could let me know some example of how to apply the multipole element on the quadrupole magnet to see that aberration. 
• For instance, do you have some nonlinear field of the quadrupole magnet, and the example of multipole with specific strength?

I am wondering if there is a way to add the fringe field on the quadrupole magnet. If there is, could you please let me know?

Thank you very much, and I am looking forward to hearing from you!

Best regards,

Seongyeol