How to use the Kinetic-fluid Hybrid Model

[cuphyalex]

Hi,

How do I use this model for the injection of electrons? Do I inject them the same as without "algo.maxwell_solver = hybrid"? How does WarpX recognize my injected electrons as electrons and treat them as a fluid?

[cuphyalex]

For now, I only inject ions, but no electrons. However, I couldn't get it running because I received this:

ERROR : Non-finite value detected in E-field; this indicates more substeps

should be used in the field solver.

!!!
SIGABRT
See Backtrace.0.0 file for details

This is my input file:
3d_magnetic_nozzle.txt

[n01r]

Hi @cuphyalex,

In the hybrid Ohm solver model, electrons are not represented explicitly as a species. Rather, Ohm's law is solved under the assumption that $n_e \approx n_i$ (quasi-neutrality) and terms of order $m_e / m_i$ are neglected, making electrons a neutralizing fluid without inertia.

Initializing electrons as a kinetic species would cause you to have to resolve the electron dynamics, and therefore get rid of the benefit that the hybrid model offers, which is stepping at ion timescales.

https://warpx.readthedocs.io/en/latest/theory/models_algorithms/kinetic_fluid_hybrid_model.html

[n01r]

I quickly adapted the input a bit. This will run, and then the beam will blow up. It's certainly a fickle solver and one needs to be aware of resolution limits with respect to ion cyclotron frequency, ion plasma frequency, and resolving the whistler criterion with the const_dt/substeps.
inputs_test_3d_hybrid_magnetic_nozzle.txt