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Large discrepancy between ECNX & ENX

Posted: 02 Sep 2014, 16:42
by Zamank
Hi All,

Pretty curious over some odd data. I basically have some accelerating structures and a chicane (standard 4-dipole), despite the fact that the dispersion is cancelling at the end of the chicane the ENX>>ECNX.

Any ideas of what could be causing the discrepancy between the ecnx and enx?

Re: Large discrepancy between ECNX & ENX

Posted: 16 Sep 2014, 11:42
by michael_borland
Sorry for the delayed reply. I was on vacation.

The problem is that although the dispersion is nominally cancelled, CSR kicks inside the chicane introduce correlations between x and delta. This probably originates in the last two dipoles, where the bunch is short. See attached plots.
x-delta.png
s16.png
--Michael

Re: Large discrepancy between ECNX & ENX

Posted: 19 Nov 2014, 17:52
by Zamank
Hi Michael,

So, the ECNX over compensates and subtracts off these CSR-induced correlations? Am I correct in stating that in this case ENX would be a more accurate depiction of the transverse emittance?

Thanks

Re: Large discrepancy between ECNX & ENX

Posted: 05 Dec 2014, 05:05
by michael_borland
Yes, that's right. ECNX is just the ideal value you'd get if you somehow managed to remove all the correlations.

--Michael