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