Modelling of plasma momentum transference to side-walls by neutral particles

Monte Carlo modelling of plasma extinction by neutral particles requires energy and momentum sinks to be determined with sufficient statistical significance. We focus on this aspect using calculations of an idealized 1-D plasma-gas interface with the EIRENE code. A novel non-linear version including self-collisions amongst neutral particles is also applied to admit gas viscosity. It emerges that statistically significant momentum losses often cannot practicably be determined, even at modest plasma temperatures (∼ 10 eV), using conventional collision-estimator techniques. Gas viscosity effects also tend to inhibit extraction of plasma momentum and hinder extinction. Certain possibilities to improve numerical methods are mentioned. (UK)