Fluid descriptions of plasmas, which are usually applied to a collisional plasma, can
only be justified for very small Coulomb Knudsen numbers. However, the scrape-off
layer (SOL) plasmas of experimental magnetic confinement fusion devices tend to
have operational regimes characterized by a Coulomb Knudsen number around 0.1.
In interesting detached regimes of an SOL plasma in a tokamak, when the plasma
detaches from the limiters or divertors, this number may increase along with the
local plasma gradients. Plasma gradients are also known to increase (and thus
drive non-local effects) in inertial confinement fusion. Neutrals, which are being
produced owing to plasma recombination at the plasma–divertor interface, may
be in a mixed collisional regime as well. Thus simultaneous kinetic treatments of
plasma and neutral particles with self-consistent evaluation of boundary conditions
at the material walls are required. We present a physical model and a numerical
scheme, and discuss results of purely kinetic simulations of plasmas and neutrals
for actual conditions in the Alcator C-Mod and Tokamak-de-Varennes experimental
tokamaks. Results for both steady-state and transient regimes of SOL plasma flow
are presented. Our approach, unlike particle-in-cell and Monte Carlo methods, is
free from statistical noise.
A comparison of non-local electron transport models for laser-plasmas relevant to inertial confinement fusion