A new tool for two-dimensional field-reversed configuration equilibrium study

TL;DR

This paper introduces GSEQ-FRC, a new computational tool for analyzing two-dimensional equilibrium states of field-reversed configurations, incorporating external coils and flexible boundary conditions for rapid equilibrium reconstruction.

Contribution

The paper presents GSEQ-FRC, a novel tool that combines a modified rigid rotor model with advanced numerical methods to efficiently study FRC equilibrium properties.

Findings

GSEQ-FRC accurately models FRC equilibrium with fixed and free boundary conditions.

The tool reveals how FRC shape transitions from racetrack-like to ellipse-like.

Quantitative analysis of factors influencing FRC separatrix shape.

Abstract

A new tool (GSEQ-FRC) for solving two-dimensional (2D) equilibrium of field-reversed configuration (FRC) based on fixed boundary and free boundary conditions with external coils included is developed. Benefiting from the two-parameter modified rigid rotor (MRR) radial equilibrium model and the numerical approaches presented by [Ma et al, Nucl. Fusion, 61, 036046, 2021], GSEQ-FRC are used to study the equilibrium properties of FRC quantitatively and will be used for fast FRC equilibrium reconstruction. In GSEQ-FRC, the FRC equilibrium can be conveniently determined by two parameters, i.e., the ratio between thermal pressure and magnetic pressure at the seperatrix $\beta_s$, and the normalized scrape of layer (SOL) width $\delta_s$. Examples with fixed and free boundary conditions are given to demonstrate the capability of GSEQ-FRC in the equilibrium calculations. This new tool is used to quantitatively study the factors affecting the shape of the FRC separatrix, revealing how the FRC changes from racetrack-like to ellipse-like.