Help Simulating Bunch Compressor & Chirp

[Zamank]

Hi All,

Needed some help trying to simulate a gaussian bunch with

Ss_initial=1.485751e-004

Ss_final~8e-006

I have attached the lte and ele files that I have been using/editing. ANy help would be greatly appreciated, thank you.

[michael_borland]

You need to optimize both the chicane and the chirp to achieve this. Attached is an example of how to do this.

--MIchael

[Zamank]

Hi Michael,

I'm trying to simulate a beamline that I already have up to the compressor; I'd like to keep the BC parameters constant but still have the same amount of compression. I know how to do this with the RF cavities before the BC, but now that I have deleted them and I am generating a gaussian bunch right before the compressor I am having a little trouble understanding how to do that.

Maybe I am not understanding the code you attached correctly but the results do not give a final bunch length of ~8um.

So, in a nutshell I want to chirp the beam to cmpress it to ~8um with the same chicane. Any advice?

PS. Also, in my original files I tried to use the momentum_chirp parameter to compress the beam so instead of 60, I believe it should be 0. Would this change alpha_z to zero as well?

[michael_borland]

Unfortunately, when compressed to this degree the bunch exhibits second-order effects, so the linear analysis inherent in the &moments_output command doesn't suffice. Actually, optimization using tracking directly (see attached) indicates that you can't get such a short bunch, because of the higher-order effects.

--Michael

[Zamank]

HI Michael,

Yes, I was afraid that would be the result...because no matter what I tried I couldn't get it to compress to that bunch length.

My goal was to study the compression of the bunch without any upstream (before the compressor) effects (space charge, CSR, ISR, wakefields...etc). What I did to finally get some reasonable results was to approximate the accelerating cavities with a lot of effects shut off, This got me a reasonable compression and energy at the end of the chicane...

Let me know what you think!