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Re: [Opal] OPAL Dispersion Issues

Chronological Thread 
  • From: "Nesteruk Konrad Pawel (PSI)" <konrad.nesteruk AT>
  • To: Ryan Roussel <roussel AT>
  • Cc: "opal AT" <opal AT>
  • Subject: Re: [Opal] OPAL Dispersion Issues
  • Date: Mon, 16 Apr 2018 09:51:30 +0000
  • Accept-language: en-US, de-CH
  • Authentication-results: localhost; dmarc=skipped

Dear Ryan,

I also had problems with correct dispersion evaluation. I use OPAL-CYC and in my case the problem was due to the fact that OPAL gives you particle coordinates in time steps and you cannot easily measure the distance between the on-momentum track and the dispersive one (although my “probe” track for the dispersion calculation was only 1% off). I do not know how you evaluate dispersion but make sure you consider the geometrical distance between simulated particles, independent of time. To do this properly, I wrote an algorithm for post-processing. If you think that your problems can be due to the same reason you can contact me privately.

Best regards,
Paul Scherrer Institut
Dr. Konrad Pawel Nesteruk
WBGA / C32
CH-5232 Villigen PSI

Telefon: +41 56 310 33 85
E-Mail: konrad.nesteruk AT

On 10 Apr 2018, at 23:43, Ryan Roussel <roussel AT> wrote:

Hello all,
I am having difficulty obtaining correct physical results with OPAL-T involving dipole magnets. I have attached the relevant files.

The beamline is a single dogleg with two equal strength bend magnets. The issue I am seeing is in the calculation of the dispersion function and the final particle distribution. The dispersion contribution from the first dipole magnet is orders of magnitude lower than what it should be, while the second dipole contributes something reasonable. On the other hand the particle phase space distribution between the dipoles looks correct for a dispersion section but the final particle distribution after the second dipole looks incorrect as it is not symmetrical. 

Note: My graph x-axes have been cut off for some reason both labels are z(m).

Any help on this issue would be greatly appreciated.
Ryan Roussel

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