The OPAL Discussion Forum

[Chris Hall <chall AT radiasoft.net>]

Hi Bettina,

Sorry, I should have mentioned that I been seeing this emittance growth in the absence of space charge (fieldsolver turned off). 

Originally, I was trying to simulate an asymmetric chicane with quads used to restore achromaticity. However, I was seeing unexplained emittance growth.

Trying to make sure I can correctly set up the lattice, I have now reduced all the way down to just a simple, symmetric chicane, running without space charge. That I see emittance growth still in this case led me to believe I am making a mistake somewhere in my setup.

Christof offered to take a look at my input file so hopefully he will be able to find where I am going astray.

Thanks,

 Chris

On Tue, Oct 31, 2017 at 3:23 AM, Kuske, Bettina <bettina.kuske AT helmholtz-berlin.de> wrote:

Hi Chris, 

Try to turn the space charge off.

If it is achromatic then, your have a problem with what we call space charge dispersion. Due to the nonlinear, defocussing effect of space charge the chicane is not closed anymore. You can only try to minimize it, and you will find emittance growth. 

What do you need the chicane for? 

Bettina

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-------- Ursprüngliche Nachricht --------

Von: Chris Hall

Datum:31.10.2017 00:00 (GMT+01:00)

An: opal AT lists.psi.ch

Betreff: [Opal] Example of a chicane?

Hello,

I was wondering if anyone has an example of standard 4 dipole bunch compression chicane implemented in OPAL 1.6?

There is a chicane in regression-tests but it is currently listed as broken. I have tried several implementations of my own but the result never appears to be achromatic and I see emittance growth if my bunch has any energy spread.

Thank you,

  Chris

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