Modeling of neutral plasma in a divertor in the fluid-kinetic transition

The neutrals in a tokamak divertor in the so‐called “detached” mode of operation may be in a kinetic regime (long mean free path) in some regions and in a fluid regime (short mean free path) elsewhere. For example, a kinetic description is necessary in the thin ionization front, while the cold neutrals in front of the divertor plate are adequately described by fluid equations. The paper describes a way to model this by coupling existing Monte Carlo neutral transport and plasma fluid codes. This is explored with a simple analytical model.