Number density for neutral particles in PICMI

[Aratopn]

Greetings!

I'm looking for a way to get the number density for neutral particles in each cell (to get density distribution). I am using PICMI with 2D geometry.

As far as I understand, I need to use ParticleContainerWrapper in some way. However, I don't understand if its output is connected with cells or just with an array of particles and their parameters. If the second option is used, then all that remains is to use their positions to determine which cells they belong to.

Maybe there are some simpler ways?

Thank you for your time.

[roelof-groenewald]

Hi @Aratopn.

If you need the neutral number density during a simulation there is support coming in #6143 that would allow you to do:

        pc = particle_containers.ParticleContainerWrapper("species_name")
        n_mf = pc.particle_container.get_number_density(lev=0)

the n_mf object is a MultiFab which you can access like a numpy array.

If you are content to get the number density as a diagnostic output, you can use the particle_fields_to_plot functionality of the Field Diagnostics (see https://warpx.readthedocs.io/en/latest/usage/parameters.html#full-diagnostics). For the number density you would set the parser function to 1/cell_volume. Let me know if you have any questions on that.

[roelof-groenewald]

Btw there was some discussion a while back about adding support for outputting the number density - see #3654.