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

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  • From: Dragos Constantin <Dragos.Constantin AT>
  • To: Simon Friederich <sifriede AT>, "Adelmann Andreas (PSI)" <andreas.adelmann AT>
  • Cc: "opal AT" <opal AT>
  • Subject: RE: [Opal] DC gun simulation: Unexpected longitudinal phase spaces
  • Date: Fri, 11 Sep 2020 16:00:08 +0000
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Hi Simon,

I supposed you have checked that the points inside the field maps are correctly ordered, e.g. for 3D field maps the z coordinate is the fastest and, y is next , and x is the slowest.


Did you try to normalize the field map?






Dragos Constantin, PhD
Sr. Research Scientist


Varian Medical Systems
3120 Hansen Way, MS G201, Palo Alto, CA 94304 United States

dragos.constantin AT
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From: opal-request AT <opal-request AT> On Behalf Of Simon Friederich
Sent: Friday, September 11, 2020 1:36 AM
To: Adelmann Andreas (PSI) <andreas.adelmann AT>
Cc: opal AT
Subject: Re: [Opal] DC gun simulation: Unexpected longitudinal phase spaces


Good morning Andreas,

Please follow this link to the fieldmaps (named cst2opal_100keV_xyz_3DDynamic.t7 and cst2opal_100keV_xz_2DDynamic.t7)

Best regards,


Am 11.09.2020 um 10:24 schrieb Adelmann Andreas (PSI):

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



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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