EFIT tokamak equilibria with toroidal flow and anisotropic pressure using the two-temperature guiding-centre plasma

TL;DR

This paper introduces an advanced force balance model for tokamak equilibria that incorporates toroidal flow and pressure anisotropy, extending the EFIT equilibrium reconstruction to more realistic plasma conditions.

Contribution

The paper presents a novel EFIT-based model including full toroidal flow and anisotropic pressures, with an analytical solution and benchmark results demonstrating its effectiveness.

Findings

Model converges similarly to standard EFIT

Analytical solution for non-zero flow and anisotropy

Benchmark results show comparable speed and accuracy

Abstract

A new force balance model for the EFIT magnetohydrodynamic equilibrium technique for tokamaks is presented which includes the full toroidal flow and anisotropy changes to the Grad-Shafranov equation. The free functions are poloidal flux functions and all non-linear contributions to the toroidal current density are treated iteratively. The parallel heat flow approximation chosen for the model is that parallel temperature is a flux function and that both parallel and perpendicular pressures may be described using parallel and perpendicular temperatures. This choice for the fluid thermodynamics has been shown elsewhere to be the same as a guiding centre kinetic solution of the same problem under the same assumptions. The model reduces identically to the static and isotropic Grad-Shafranov equation in the appropriate limit as different flux functions are set to zero. An analytical solution based on a modified Soloviev solution for non-zero toroidal flow and anisotropy is also presented. The force balance model has been demonstrated in the code EFIT TENSOR, a branch of the existing code EFIT++. Benchmark results for EFIT TENSOR are presented and the more complicated force balance model is found to converge to force balance similarly to the usual EFIT model and with comparable speed.