Multi-temperature Generalized Zhdanov Closure for Scrape-Off Layer/Edge Applications

TL;DR

This paper derives a multi-temperature generalized Zhdanov closure for plasma modeling, explicitly outlining the assumptions, and compares its effectiveness with previous single-temperature schemes for fusion applications.

Contribution

It introduces a comprehensive multi-temperature closure scheme with explicit derivation and validation against single-temperature models in fusion-relevant plasma conditions.

Findings

21N-moment multi-temperature coefficients are sufficient for most fusion cases.

The multi-temperature scheme outperforms single-temperature models in accuracy.

The closure scheme's validity is confirmed within the trace approximation for fusion plasmas.

Abstract

The derivation of the multi-temperature generalized Zhdanov closure is provided starting from the most general form of the left hand side of the moment averaged kinetic equation with the Sonine-Hermite polynomial ansatz for an arbitrary number of moments. The process of arriving at the reduced higher-order moment equations, with its assumptions and approximations, is explicitly outlined. The generalized multi-species, multi-temperature coefficients from the authors' previous article are used to compute values of higher order moments such as heat flux in terms of the lower order moments. Transport coefficients and the friction and thermal forces for magnetic confinement fusion relevant cases with the generalized coefficients are compared to the scheme with the single-temperature coefficients previously provided by Zhdanov et al. It is found that the 21N-moment multi-temperature coefficients are adequate for most cases relevant to fusion. Furthermore, the 21N-moment scheme is also tested against the trace approximation to determine the range of validity of the trace approximation with respect to fusion relevant plasmas. Possible refinements to the closure scheme are illustrated as well, in order to account for quantities which might be significant in certain schemes such as the drift approximation.