DSMC excitation collision error in BinaryCollision::doCollisionsWithinTile

[zhongerting]

I'm encountering an error when trying to set up a DSMC-type excitation collision. The simulation fails in BinaryCollision::doCollisionsWithinTile with the following TinyProfilers stack trace:

text
===== TinyProfilers ======
main()
REG::WarpX::Evolve()
WarpX::Evolve()
WarpX::Evolve::step
WarpX::OneStep()
MultiParticleContainer::doCollisions()
BinaryCollision::doCollisionsWithinTile

My DSMC excitation input is configured as:
collision2.type = dsmc
collision2.scattering_processes = excitation1
collision2.species = electrons cesium_atoms_6s1_2
collision2.product_species = electrons cesium_atoms_6p3_2
collision2.excitation1_energy = 1.2584000
collision2.excitation1_cross_section = [directory is correct]
Has anyone encountered a similar issue, or can spot any potential problems with this configuration? Any insights would be appreciated.

[roelof-groenewald]

Hi @zhongerting. Unfortunately excitation collisions are not yet supported in WarpX's DSMC module. There is some effort ongoing to generalize the product producing reactions, and with that it will be fairly easy to add excitation collisions.

[zhongerting]

Thank you for the explanation. I have another question: If I want to study excitation to multiple states and multi-step ionization, is that possible with the current modules in WarpX?

[roelof-groenewald]

Currently multi-step ionization is not supported in WarpX. To add it we need to extend the "product producing" reactions to include excitation and add some mechanism for atoms to de-excite.

[zhongerting]

Thank you for your response and contributions. I have a question regarding the code related to the excitation module of background_mcc. In background_mcc, how are the excited state atoms produced by excitation stored? Why is the excited state product not specified when defining the excitation for background_mcc type collisions (referencing the warpx/Examples/Tests/embedded_circle/inputs_test_2d_embedded_circle file)?

By the way, if the excited state atoms produced can be recorded, would it be possible to set up ionization for these excited atoms using the DSMC method to achieve multi-step ionization?

[Yin-YinjianZhao]

@roelof-groenewald BTW, I'm also trying to use the DSMC feature, and found it may have a bug affected by the MPI domain decomposition. For example, I got this ion density result (log10(ni)) when using 8 partitions in r and 16 in z.

[RemiLehe]

@Yin-YinjianZhao
Thanks for reporting this issue. This is definitely unexpected.
Would you be able to share an inputs script that we could run to reproduce and debug this issue?

[Yin-YinjianZhao]

@RemiLehe I tested this script and got the above result. You don't have to run such a big test or long time to get it I believe. Hope this is helpful :)
picmi.txt

[Yin-YinjianZhao]

BTW, can WarpX output the density field rather than the charge density field? Because neutral particles should have zero charge, so the rho_neutrals will give zero fields. In the script above, I set neutrals a small charge (e*1e-6) for making plots using rho_neutrals.