Speaker
Description
In plasma boundary modelling, fluid neutrals offer several practical disadvantages compared to their more accurate kinetic Monte Carlo counterparts. They are typically much faster, and their deterministic nature is a major benefit when doing optimization or when coupling to plasma turbulence codes.
Besides missing kinetic effects, fluid neutral models are typically also lagging behind with regard to the physics processes they include. The vast majority of present-day fluid neutral models consider only atoms.
The first commonly referenced fluid molecular models in the context of plasma edge models were developed in UEDGE. The UEDGE work focused primarily on the details of the molecular physics (Collisional Radiative Models) and their impact on detachment in DIII-D, while the benchmark with EIRENE was more restricted. In this contribution, we aim for a complementary approach, considering only the default molecular physics model from EIRENE, but performing for the first time a thorough benchmark between the fluid model and EIRENE for all macroscopic parameters (density, velocity and temperature) and all exchange terms with the plasma and atom populations (ion/atom particle sources, ion/atom parallel momentum sources, electron energy sources and ion/atom energy sources), on a plasma background representative of the detached regime.
We show that the particle velocity distribution of the kinetic molecules approaches a Maxwellian in a large part of the relevant domain, due to the elastic collisions with the detached plasma background. We also show that the bulk of the molecular physics can be captured reasonably well with the presented fluid molecular model, showcasing it to be an excellent starting point for further research in this direction.