Emittance Decrease After Bunch Compressor With CSR?

[Zamank]

Hi,

I am looking at various chicane configurations and their effects on CSR emittance growth, and I ran into a configuration that shows a decrease in x-plane emittance which I am having a hard time to explain physically.

I have attached the chicane and input beam. I was wondering if you had any thoughts?

Thanks in advance!

[michael_borland]

I see a very small decrease in the emittance when I run your simulation. My explanation is that there are some correlations in your input beam that just happen to be cancelled by CSR effects. This could happen, for example, when the phase ellipse rotates in just the right way along the bunch.

One way to see that this might be the case is by reversing time and momentum offsets of the particles

Code: Select all

sddsprocess input.out input.rev -redefine=col,t,"t -1 *",units=s -process=p,ave,pAve -redefine=col,p,"pAve p pAve - -"

then running again. The bunch is still compressed, but now the emittance increases slightly.

--Michael