Linear chirp in X-P phase space

[Jafarinia]

Hi all,

I am trying to get a linear chirp in X-P phase space. Which parameters should I optimize to get that?

Thanks,
Farzad

[michael_borland]

Farzad,

I'm not sure if you are referring to an initial beam distribution or the distribution at the end of a beamline. Assuming that by 'P' you mean the total momentum of the particles, you want to maximize the dispersion function. If you give more detail about what you are trying to do, I might be able to give more helpful advice.

--Michael

[Jafarinia]

Hi Michael,

I want to give dispersion to the beam by a dipole and also optimize the twiss parameters at the end of the beam line. Due to initial energy spread and quadrupoles in the beam line the chirp in X-P phase space is not linear (curved shape like banana) and so I need to use sextupole to minimize non-linearity. I was wondering which parameter should I minimize/maximize to get linear chirp in X-P phase space?
I realized that by minimizing the Sxp the chirp (X-P) would be linear but not in all cases.

Thanks,
Farzad

[michael_borland]

Farzad,

Attached is an example of one way to do this. In summary, the method is

1. Insert a SCRIPT element at the end of the beamline, with the script command designed to remove the linear correlations (x,p) and (xp, p)
2. Minimize the horizontal emittance of the resulting beam by adjusting sextupoles.

I hope something along these lines will work for your problem. Another approach is to minimize the higher-order terms in the transport matrix. However, that is less direct and requires knowing which terms actually matter.

--Michael

[michael_borland]

Farzad,

Actually, I realized that there is a better way to do this. The REMCOR element already provides the function that I implemented using a SCRIPT. See attached.

--Michael

[Jafarinia]

Hi Michael,

Thanks a lot....brilliant way.
I used REMCOR at the end of the beam line and then tried to minimize horizontal emittance of the resulting beam by sextupole.

Thanks,
Farzad