Towards a unified linear kinetic transport model with the trace ion module for EIRENE

TL;DR

This paper introduces a unified kinetic transport model for fusion plasma simulations that integrates neutral and ion particle transport into a single Monte Carlo code, simplifying interfaces and ensuring consistency.

Contribution

It proposes a novel scheme to combine neutral and ion transport modules into one code despite their different mathematical forms, improving simplicity and consistency.

Findings

Unified code can handle typical fusion edge plasma conditions.

Approximations are acceptable within certain plasma regimes.

Simplifies the integration of atomic and surface processes.

Abstract

Linear kinetic Monte Carlo particle transport models are frequently employed in fusion plasma simulations to quantify atomic and surface effects on the main plasma flow dynamics. Separate codes are used for transport of neutral particles (incl. radiation) and charged particles (trace impurity ions). Integration of both modules into main plasma fluid solvers provides then self consistent solutions, in principle. The required interfaces are far from trivial, because rapid atomic processes in particular in the edge region of fusion plasmas require either smoothing and resampling, or frequent transfer of particles from one into the other Monte Carlo code. We propose a different scheme here, in which despite the inherently different mathematical form of kinetic equations for ions and neutrals (e.g. Fokker-Planck vs. Boltzmann collision integrals) both types of particle orbits can be integrated into one single code. We show that the approximations and shortcomings of this "single sourcing" concept (e.g., restriction to explicit ion drift orbit integration) can be fully tolerable in a wide range of typical fusion edge plasma conditions, and be overcompensated by the code-system simplicity, as well as by inherently ensured consistency in geometry (one single numerical grid only) and (the common) atomic and surface process modules