Elegant users forum

Dear Michael Borland and every one.

Hello. I have a one questions.
I want to simulate the dynamic aperture with multipole errors of magnet.
I already know to contain the multipole error in quad and sextupole magnet.
But, The dipole manget don't know. Could explain to me?
Have a nice days.

Sincerely yours.

Hwang, Ji-Gwang

Ji-Gwang,

For dipoles, you can use the CSBEND element and provide values to the K1, K2, ..., K8 parameters. Equivalently, you can provide values for B1, B2, ..., B8.

--Michael

Hello,
I have a question related to this. I want to add the multipoles calculated from a measured field map of dipoles in a chicane. I did the polynomial expansion around the reference trajectory for each z and I calculated some coefficients b_n defined from:
B = 1/n!*(d^nB/dx^n)*x^n
my coefficients are then
b_n = 1/n!*(d^nB/dx^n)
The ones defined in the manual are given by:
By = B0+(1+sum(b_n/n!*x^n))
If I am not mistakening:
B_n = n!*b_n/B0
are the B_n I have to put in Elegant.
The question is: "How are these B_n treated? Are they the integral along the field map length in z renormalized by the dipole length?"
Thanks for your answer,
Simona.

Simona,

Just to be clear, the Bn that you input to elegant are normalized with the field on the central orbit and are given by derivatives. I.e., bn = d^n/dx^n (By(x,y=0)/B(x=0,y=0)). I'm not sure the expressions you gave are quite right.

These fields are distributed through the body of the magnet, I.e., at each point along the arc, the field is assumed to be given by the the expression By(x,y=0) = B0*(1 + sum bn*x^n/n!). If you have integrals of the field along curved paths, then normalizing the coefficients of a polynomial vs x to the length is a good approach. You could also just to the fit to By(x) at the center of the magnet, which assumes that the harmonic content is the same throughout the magnet.

Hope this helps.

--Michael

Hello,

I want to calculate DA in the presence of harmonic field error, I understand that the dipole error can be considered by k1,k2,k3... and quad and sextupoles error will be considered by sdds file.
I have two question, Is it possible to calculate magnets error in ELEGANT?
why the sdds file of magnet's error can't be read in my file which is attached?
Thanks in advance
Sara

Sara,

Your input files had two errors:
1. The name of the multipole input file in the lattice file needs to be quoted. Otherwise, it is translated into all upper-case letters, which won't work on systems (e.g., Linux) where filenames are case-sensitive.
2. The quadSysMult.sdds file was not a valid SDDS file. The row-count parameter was 14, but only 10 rows were present. Plus, the value of order in the second row was 0, but should have been 1.

See attached.

I'm not sure what you mean by "Is it possible to calculate magnets error in ELEGANT?". Can you clarify your question?

--Michael

Thanks Micheal to answer my question.
Now I can calculate the Dynamic Aperture by considering quadrupoles and dipole error, But the beta-y become zero, when I remove the dipole error from my lattice the beta-y is not zero. I was thinking maybe it's because of considering dipole error as k1,k2,...? Do we have any other way to consider field harmonic error of dipole?
About my second question, I just enter the errors which is calculated by OPERA in my ELEGANT lattice, I want to know that Is it possible to calculate field harmonic error in ELEGANT or not? As I'm seeking in ELEGANT examples, I don' find any thing.

Cheers,
Sara

michael_borland wrote: ↑

22 May 2018, 17:13

Sara,

Your input files had two errors:
1. The name of the multipole input file in the lattice file needs to be quoted. Otherwise, it is translated into all upper-case letters, which won't work on systems (e.g., Linux) where filenames are case-sensitive.
2. The quadSysMult.sdds file was not a valid SDDS file. The row-count parameter was 14, but only 10 rows were present. Plus, the value of order in the second row was 0, but should have been 1.

See attached.

I'm not sure what you mean by "Is it possible to calculate magnets error in ELEGANT?". Can you clarify your question?

--Michael

Sara,

I'm very puzzled how beta-y could be zero. Can you provide set of files that show this?

In answer to your question, there is no way to compute field errors in elegant; using OPERA is a good approach.

--Michael

Dear Michael
I understand the problem. The problem was in the way that I put dipole error in the lattice.
Thanks a lot for your help.

cheers,
Sara

michael_borland wrote: ↑

25 May 2018, 07:58

Sara,

I'm very puzzled how beta-y could be zero. Can you provide set of files that show this?

In answer to your question, there is no way to compute field errors in elegant; using OPERA is a good approach.

--Michael