A Drift-Kinetic Analytical Model for SOL Plasma Dynamics at Arbitrary Collisionality

TL;DR

This paper develops a comprehensive drift-kinetic model for SOL plasma dynamics in tokamaks that accurately captures behavior across all collisionality regimes using a gyroaveraged Lagrangian approach and a Hermite-Laguerre velocity space decomposition.

Contribution

It introduces a novel drift-kinetic model incorporating a full Coulomb collision operator and a Hermite-Laguerre decomposition, enabling analysis of plasma far from equilibrium at arbitrary collisionality.

Findings

Model accurately describes plasma dynamics across collisional regimes.

Explicit evaluation of Coulomb collision moments allows studying far-from-equilibrium distributions.

Fluid closure derived for high-collisionality limit, matching existing models.

Abstract

A drift-kinetic model to describe the plasma dynamics in the scrape-off layer region of tokamak devices at arbitrary collisionality is derived. Our formulation is based on a gyroaveraged Lagrangian description of the charged particle motion, and the corresponding drift-kinetic Boltzmann equation that includes a full Coulomb collision operator. Using a Hermite-Laguerre velocity space decomposition of the gyroaveraged distribution function, a set of equations to evolve the coefficients of the expansion is presented. By evaluating explicitly the moments of the Coulomb collision operator, distribution functions arbitrarily far from equilibrium can be studied at arbitrary collisionalities. A fluid closure in the high-collisionality limit is presented, and the corresponding fluid equations are compared with previously-derived fluid models.