Elegant vs AT MA and Touschek lifetime

[ranamonikaa]

Hi,
I calculated the Touschek lifetime for an example lattice using both Elegant and AT, and plotted the results for different RF voltages. I observe that the lifetimes obtained from the two codes show noticeable differences. From further analysis, I found that the momentum aperture computed in Elegant is lower compared to AT, which seems to explain why the Touschek lifetime predicted by Elegant is correspondingly smaller. I used element-by-element synchrotron radiation calculations in Elegant by enabling radiation locally using SYNCH_RAD = 1, ISR = 0 for the CSBEND, KQUAD, and KSEXT elements. I also placed rf cavities in the right location in the lattice, that too didn't resolve the discrepancy.

I have attached the plot showing the variation of Touschek lifetime with RF voltage.

I would appreciate insights on the following:

1. What could cause the difference in momentum aperture between Elegant and AT?

2. Are there known differences in tracking, radiation treatment, or aperture evaluation that could lead to this?

Thank you.

-Monika

[michael_borland]

Monika,

We did a comparison of AT and elegant several years ago and found good agreement in the LMA.
https://journals.aps.org/prab/pdf/10.11 ... .22.114601

However, we didn't compute the Touschek lifetime for each case and unfortunately, I don't have those files any longer. The Touschek lifetime can be quite sensitive to small changes in LMA, especially when the LMA is not large. Can you compare the LMA for a case with large rf voltage (so the rf bucket doesn't enter into the result)?

Also, how similar are the LMA search parameters in the two codes? How about integration parameters and integrator order on the individual elements?

--Michael