Experimental and simulation studies of collisionless plasma flow

Summary form only given, as follows. In modeling the steady-state flow of a collisionless plasma or an ion beam from a source region into a source-free area by means of the Poisson-Vlasov equations, a nonphysical buildup of positive charge occurs a short distance away from the discharge point and soon acts to impede further flow out of the source. Such an occurrence is seldom seen in the laboratory, and an appropriate electron model is needed to mitigate this effect. The authors have had some success with a two-population electron model composed of a primary species that streams from the source (Vlasov) and a secondary species that is scattered from the primary. The contribution of the secondary population is negligible, except in instances in which electron trapping can occur. The electrons are then modeled as having a truncated equilibrium energy distribution. The obtained simulation results correlate quite well with the values measured in the laboratory.<>