Nonlinear Transport Processes in Tokamak Plasmas. Part I: The Collisional Regimes

TL;DR

This paper applies thermodynamic field theory to derive nonlinear corrections to collisional transport coefficients in tokamak plasmas, revealing significant enhancements in electron transport predictions compared to neoclassical theory.

Contribution

It introduces nonlinear corrections to transport coefficients in collisional regimes using TFT, highlighting asymmetries between ion and electron transport not captured by classical models.

Findings

Nonlinear electron P-S transport coefficients exceed neoclassical values by up to 100 times.

Nonlinear classical coefficients are about twice the neoclassical predictions.

Ion transport coefficients remain consistent with neoclassical theory.

Abstract

An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear (Onsager) transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for JET plasmas are also reported. We found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor, which may be of the order 100. The nonlinear classical coefficients exceed the neoclassical ones by a factor, which may be of order 2. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes i.e., the plateau and the banana regimes, are analyzed in the second part of this work.