Four-dimensional drift-kinetic model for scrape-off layer plasmas

TL;DR

This paper derives a comprehensive four-dimensional drift-kinetic plasma model for the scrape-off layer in tokamaks, incorporating full Coulomb collisions and far-from-equilibrium effects, using a Laguerre polynomial expansion.

Contribution

It introduces a novel four-dimensional drift-kinetic model that includes the full Coulomb collision operator and arbitrary far-from-equilibrium distributions.

Findings

Explicit formulation of Coulomb collision operator in velocity moments

Derivation of four-dimensional moment equations for plasma distribution

Model applicable at arbitrary collisionality in tokamak scrape-off layer

Abstract

A four-dimensional plasma model able to describe the scrape-off layer region of tokamak devices at arbitrary collisionality is derived in the drift-reduced limit. The basis of the model is provided by a drift-kinetic equation that retains the full non-linear Coulomb collision operator and describes arbitrarily far from equilibrium distribution functions. By expanding the dependence of distribution function over the perpendicular velocity in a Laguerre polynomial basis and integrating over the perpendicular velocity, a set of four-dimensional moment equations for the expansion coefficients of the distribution function is obtained. The Coulomb collision operator, as well as Poisson's equation, are evaluated explicitly in terms of perpendicular velocity moments of the distribution function.