dynamic aperture after insert a wiggler

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Samira.kasaei
Posts: 23
Joined: 15 Jun 2021, 13:38

dynamic aperture after insert a wiggler

Post by Samira.kasaei » 16 Sep 2021, 05:14

Dear Michael,

I inserted a wiggler in my ring and after optimization the beam optics, I checked dynamic aperture.
Dynamic aperture before insertion a wiggler was 0.2 horizontally and 0.04 vertically while it was decreased to 0.04 horizontally and 0.008 vertically.
Do you think if I had a mistake to find dynamic aperture?

Many thanks and best regards,
Samira
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Samira.kasaei
Posts: 23
Joined: 15 Jun 2021, 13:38

Re: dynamic aperture after insert a wiggler

Post by Samira.kasaei » 28 Sep 2021, 04:41

Dear Michael,

Concerning my previous post, first I wanted to be sure that I didn't have a mistake.
Then If my run was correct , what can I do to increase dynamic aperture?

Many thanks and best regards,
Samira

michael_borland
Posts: 1811
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: dynamic aperture after insert a wiggler

Post by michael_borland » 15 Oct 2021, 10:49

Samira,

If I turn off the wiggler by setting FIELD_FACTOR=1e-10 on the UKICKMAP element, I don't see much difference in the DA. Perhaps there is some other change between your two results.

I noticed a few things about your simulations that might warrant attention:
  • The chromaticities are both negative (about -4.6).
  • You are dividing the elements, but using few slices for the CSBEND elements. This will make the simulation slower. I recommend against dividing elements unless you need the resolution for loss recording.
  • You are using the default fourth-order integrator. You can save time with the sixth-order integrator and fewer slices. See attached.
--Michael
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Samira.kasaei
Posts: 23
Joined: 15 Jun 2021, 13:38

Re: dynamic aperture after insert a wiggler

Post by Samira.kasaei » 22 Nov 2021, 07:59

Dear Michael,

I checked with accelerator toolbox and chromaticity must be +6 and+7. but as you mentioned chromaticity values given by elegant is -4.6.
Do you know the reason?

Many thanks for your answer,
Samira

Samira.kasaei
Posts: 23
Joined: 15 Jun 2021, 13:38

Re: dynamic aperture after insert a wiggler

Post by Samira.kasaei » 25 Nov 2021, 07:21

Dear Michael,

Here is my lattice with the affect of fringe field.
I do appreciate if you can take a look to my files.

Best regards,
Samira
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STORAGE.lte
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michael_borland
Posts: 1811
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: dynamic aperture after insert a wiggler

Post by michael_borland » 08 Dec 2021, 16:55

Samira,

I don't have an explanation for why the chromaticity is not what you expect. The lattice definition seems fine. (I would recommend EDGE1_EFFECTS=EDGE2_EFFECTS=4 and FSE_CORRECTION=1 on the CSBEND elements, to get the best dipole fringe model.)

I tried computing the chromaticity using tracking and it agrees very well with the values reported by &twiss_output.

Elegant and AT agree quite well on the chromatic of the APS-U lattice, which has many strong gradient dipoles. However, the bending radius is about 5x larger than yours.

I did notice that if I double the strength of both sextupole families, the chromaticities are both positive, with x=6.4 and y=5.8. Is it possible the strengths were translated incorrectly?

--Michael

Samira.kasaei
Posts: 23
Joined: 15 Jun 2021, 13:38

Re: dynamic aperture after insert a wiggler

Post by Samira.kasaei » 21 Dec 2021, 04:41

Dear Michael,

I tried with twice values with Elegant and I got the same chromaticity as yours. but our storage ring is operating at the chromaticity of 6 and 7 with sextupole gradients of 10.98 and -16.57.

I do appreciate all of your answers in this issue,
samira

simona.bettoni
Posts: 42
Joined: 06 Jul 2011, 03:14

Re: dynamic aperture after insert a wiggler

Post by simona.bettoni » 24 May 2022, 08:20

Dear Samira,
I am not really an expert in the topic, but when I tried to do the same with a collegue using another code (only now I am trying with Elegant), we noticed that the quadrupole induced by the wiggler modified the optics, and the DA was strongly reduced. We rematched using the quadrupoles around the section where we inserted the wiggler (using only the quadrupoles), and we recovered the dynamic aperture.
Maybe this is not your problem, and the high orders mode of the wiggler are really impacting your DA, but I wanted to share with you what we observed.
If you fixed already your issue, and it does not have anything to do with what I wrote, feel free to ignore my post,
Simona.

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