### TWPL increasing integration steps creates bizare behaviour

Posted:

**29 Jul 2022, 12:53**Hello all,

Has anyone else got much experience with setting the integration step number for TWPL? At first I went for adapbtable step sizes, but elegant threw a warning. After that I went to a fixed step size and it went away.

However I wanted to know how many would be suitable. For one thing, beyond a certain number of turns the beam size grows considerably in an unphysical manner, so there is an operational ceiling. I wondered if perhaps it could be extended by increasing the integration step count.

I decided to do a convergence test for my run, and got the following graph:

The files to replicate it are also included in the Zip folder, if you want to check the details for yourself.

To be clear, for the number of turns I have run here, using 25 and 250 integration steps the behaviour seems qualitiatively similar to the EVKICK element I have used in the past. To be honest, I'm open to advice if you think it is worth the bother of trying to 'accurately' model a stripline kicker? Though the underlying physics is different, the results seem kinda similar - and EVKICK at least is a well tested and symplectic method.

Has anyone else got much experience with setting the integration step number for TWPL? At first I went for adapbtable step sizes, but elegant threw a warning. After that I went to a fixed step size and it went away.

However I wanted to know how many would be suitable. For one thing, beyond a certain number of turns the beam size grows considerably in an unphysical manner, so there is an operational ceiling. I wondered if perhaps it could be extended by increasing the integration step count.

I decided to do a convergence test for my run, and got the following graph:

The files to replicate it are also included in the Zip folder, if you want to check the details for yourself.

To be clear, for the number of turns I have run here, using 25 and 250 integration steps the behaviour seems qualitiatively similar to the EVKICK element I have used in the past. To be honest, I'm open to advice if you think it is worth the bother of trying to 'accurately' model a stripline kicker? Though the underlying physics is different, the results seem kinda similar - and EVKICK at least is a well tested and symplectic method.