Question: Gyrokinetic approximation for magnetized electrons in WarpX

[kolotinsky1998]

Hello WarpX developers,

I am studying the paper “Particle-in-cell simulation of a cylindrical plasma mass separator based on Penning discharge with thermionic cathodes” (Plasma Sources Sci. Technol. 32 (2023) 095007).

In that work, the authors use a 2D3V electrostatic PIC/MCC model with a gyrokinetic approximation for magnetized electrons in order to make the simulation feasible at strong magnetic fields. I would like to model a similar system with WarpX.

My questions are:

1. Is a gyrokinetic (or drift-kinetic) approximation for magnetized electrons already implemented in WarpX?
2. If not, is there ongoing work in this direction?
3. How difficult would it be to extend WarpX to include such an approach — e.g., evolving electron gyrocenters instead of full orbits, while retaining ions in full PIC?
4. Are there recommended starting points in the WarpX codebase or related examples that could help implement this feature?

The goal is to reduce computational cost when simulating systems like Penning discharges and plasma mass separators, where electrons are strongly magnetized but ions are not.

Thank you very much for any guidance!

Best regards,
Daniil Kolotinskii

[EZoni]

Hi @kolotinsky1998,

Thanks for the questions!

A gyrokinetic or drift-kinetic approximation is not currently implemented in WarpX.

There have been discussions in the past about implementing the algorithm described in Cohen, R. H., et al. "Large-timestep mover for particle simulations of arbitrarily magnetized species." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 577.1-2 (2007): 52-57, but it has not been done yet.

Do you think that this algorithm could work well in your case?

Also, out of curiosity, in your case what features would make WarpX preferable over existing gyrokinetic PIC codes that may as well serve your purpose (e.g., ORB5, GTC, GEMPICX, etc.)?

[kolotinsky1998]

Hi @EZoni ,

Thank you very much for your reply and for pointing me to the Cohen et al. algorithm — I will look at it more closely. From what I can see, this approach does look suitable for my problem, though I’ll need to study it in more detail to be sure.

Regarding your question: I am considering WarpX as my main option because it is very well documented, actively developed, flexible, and fully open-source. By contrast, many specialized gyrokinetic codes are either partially closed, less well documented, or tied to fixed geometries, which makes them less convenient for adapting to problems such as Penning discharges or plasma mass separators.

Thanks again for the guidance!

Best regards,
Daniil Kolotinskii

[EZoni]

Pinging a few developers who may be interested in following this thread: @jlvay, @dpgrote, @RemiLehe, @roelof-groenewald.