An interesting problem in a tune footprint of FMA

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gwei
Posts: 33
Joined: 17 Jul 2015, 07:16

An interesting problem in a tune footprint of FMA

Post by gwei » 22 Nov 2017, 11:41

Hi michael,

A result of the tune footprint of FMA is shown in fma2216.png. The tune of the lattice is (.22, .16), But the top in the tune footprint plot is not.
the top in the tune footprint is like (.204, .163).
fma2216.png
Another result plot is made by LEGO. 
LEGO result.png
I changed several number parameters in the ele file, but there is not change of the strange top value of (.204, .163) in the tune footprint.
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da_fma.ele
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gwei
Posts: 33
Joined: 17 Jul 2015, 07:16

Re: An interesting problem in a tune footprint of FMA

Post by gwei » 22 Nov 2017, 11:58

And I checked the .twi file also.
the nux and nuy are .22 and .16.
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elegant.twi
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michael_borland
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Location: Argonne National Laboratory
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Re: An interesting problem in a tune footprint of FMA

Post by michael_borland » 22 Nov 2017, 12:43

Can you provide your .lte and .ele files? Otherwise, it is impossible to suggest a solution.

--Michael

gwei
Posts: 33
Joined: 17 Jul 2015, 07:16

Re: An interesting problem in a tune footprint of FMA

Post by gwei » 22 Nov 2017, 13:16

HI Michael

ele file was attached already as the first attached file. 'da_fma.ele'
I modified my question topics
Last edited by gwei on 22 Nov 2017, 13:43, edited 1 time in total.

michael_borland
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Location: Argonne National Laboratory
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Re: An interesting problem in a tune footprint of FMA

Post by michael_borland » 22 Nov 2017, 13:26

The problem is more likely to be in the .lte file. You can email it to me (borland at aps.anl.gov) if you don't want to post it.

Things to check are a sufficient number of kicks (N_KICKS parameter) on KQUAD and CSBEND elements.

--michael

gwei
Posts: 33
Joined: 17 Jul 2015, 07:16

Re: An interesting problem in a tune footprint of FMA

Post by gwei » 22 Nov 2017, 13:44

michael_borland wrote:The problem is more likely to be in the .lte file. You can email it to me (borland at aps.anl.gov) if you don't want to post it.

Things to check are a sufficient number of kicks (N_KICKS parameter) on KQUAD and CSBEND elements.

--michael
Thank you. I already email to you.

michael_borland
Posts: 1811
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: An interesting problem in a tune footprint of FMA

Post by michael_borland » 22 Nov 2017, 14:21

Guohui,

Thanks for sending the lattice. One problem is too few kicks for the quadrupoles. Some of your quadrupoles are quite long and not weak, so the lattice functions can change considerably inside them. This means you need more kicks to get a good model.

I got tunes of 0.219 and 0.160 by increasing the number of kicks by a factor of 2 on all quadrupoles. You may also try increasing this only for quads with larger K1*L.

You should also vary the value of N_KICKS on the CSBEND elements to ensure things have converged sufficiently.

--Michael

gwei
Posts: 33
Joined: 17 Jul 2015, 07:16

Re: An interesting problem in a tune footprint of FMA

Post by gwei » 22 Nov 2017, 14:24

michael_borland wrote:Guohui,

Thanks for sending the lattice. One problem is too few kicks for the quadrupoles. Some of your quadrupoles are quite long and not weak, so the lattice functions can change considerably inside them. This means you need more kicks to get a good model.

I got tunes of 0.219 and 0.160 by increasing the number of kicks by a factor of 2 on all quadrupoles. You may also try increasing this only for quads with larger K1*L.

You should also vary the value of N_KICKS on the CSBEND elements to ensure things have converged sufficiently.

--Michael

Thank you very much.

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