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Re: [Opal] DC gun simulation: Unexpected longitudinal phase spaces

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  • From: "Adelmann Andreas (PSI)" <andreas.adelmann AT>
  • To: Simon Friederich <sifriede AT>
  • Cc: "opal AT" <opal AT>
  • Subject: Re: [Opal] DC gun simulation: Unexpected longitudinal phase spaces
  • Date: Fri, 11 Sep 2020 08:24:11 +0000
  • Accept-language: en-US, de-CH

Hello Simon, I can not see an obvious mistake. Please share the 
field maps then I can have  detailed look at the problem.

Thanks & 
Cheers A
Dr. sc. math. Andreas (Andy) Adelmann
Head a.i. Labor for Scientific Computing and Modelling 
Paul Scherrer Institut OHSA/ CH-5232 Villigen PSI
Phone Office: xx41 56 310 42 33 Fax: xx41 56 310 31 91
Zoom ID: 470-582-4086 Password: AdA
Friday: ETH HPK G 28   +41 44 633 3076
The more exotic, the more abstract the knowledge, 
the more profound will be its consequences.
Leon Lederman 

On 10 Sep 2020, at 15:40, Simon Friederich <sifriede AT> wrote:

Dear OPAL-Team,

I am trying to simulate a DC electron source. I implemented a 2DDynamics fieldmap into OPAL, that I've exported from CST. Furthermore I've set the frequency to 1 Hz as shown in the DC Gun example.

Unfortunately the longitudinal phase spaces look unexpected. Here I've plotted the h5-output for the gun simulation as well as a pure drift simulation of a 100keV electron beam (same bunch sizes and parameters but the energy is fixed) as comparison.


One can see a strange saw-tooth like pattern convoluted with another almost trident-like one.

This is my emitted gaussian distribution (nothing special, I'd say):

    SIGMAR = 0.5e-3, CUTOFFR = 3,

    SIGMAT = 10.0e-12,
    NBIN = 0,  // This I've varied
    EMISSIONSTEPS=10,  // this I've varied too

Maybe you see something obvious, that I did wrong? (I've also put my input file in the attachement, the fieldmaps are quite large, if you want them I'll add a seafile link)

I've compared the Ez-field of the reference particle. It looks exactly like the one I've exported from CST. (My next idea was to dumb all E-fields and plot this, but this could be a lot of work and might not bring up the source of the problem). And I've also imported a 3DDynamics field, but there is also no difference to be seen (the source has a cylindrical symmetry, so both should work).

Best regards and thank you very much as always in advance


Dr. Simon Friederich
Helmholtz-Institut Mainz
Kollaboration B/ACID
Johannes Gutenberg-Universit├Ąt Mainz
Staudingerweg 18
55128 Mainz, Deutschland

Tel.: +49 (0)6131 39-23160
E-Mail: sifriede AT

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