The OPAL Discussion Forum

[Christopher Pierce <cmpierce AT uchicago.edu>]

Huh, interesting. I am using version 2022.1.0 (git rev. a4e0e14466557289b4f7a843fb9eb72700ff1992). Is that the development version that doesn't show the error?

Cheers,

Chris

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From: Adelmann Andreas <andreas.adelmann AT psi.ch>
Sent: Tuesday, April 4, 2023 5:44 AM
To: Christopher Pierce <cmpierce AT uchicago.edu>
Cc: opal AT lists.psi.ch <opal AT lists.psi.ch>
Subject: Re: [Opal] quaternion isn't unit quaternion. Norm: -nan

 

Hi Chris great that OPAL is of help to your research! 

And yes your original field map is special :), indeed. 

I can reproduce and confirm that with a small Ez component OPAL is 

running well. I do not see however, the error you encountering. What version of OPAL 

are you using? 

Cheers A
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On 4 Apr 2023, at 05:53, Christopher Pierce <cmpierce AT uchicago.edu> wrote:

Hey folks,

First, I have recently started using opal and wanted to thank you for it. It looks like it will be very useful for my research.

I am emailing because I am running into a problem with the attached input file. It is supposed to represent a beam in a artificial electrostatic focusing channel. I do this by loading a fieldmap into the simulation with a constant negative radially pointing E-field and no Ez component.

The problem I encounter is that after loading the input file, the program returns the error "quaternion isn't unit quaternion. Norm: -nan". 

I found out that I can make the error go away by setting a single element of the fieldmap to have finite Ez (also attaching the file as "e-lens-fixed.T7". This fieldmap seems to give me the results I expect. Is there something that I am doing wrong here?

Cheers,

Chris Pierce

<20230403-opal-focusing-channel.txt><e-lens.T7><e-lens-fixed.T7>