Anatomy of a field-reversed configuration

Abstract

A reconstructor tool is developed for fast computation of fully two-dimensional equilibria of field-reversed configurations (FRCs) that are consistent with routine magnetic data from experiments. This tool fosters physical interpretation of multiple FRC properties. The physics model is a rotating fluid that also captures several realistic kinetic effects. The tool allows both FRC solutions and high-β mirror solutions (no closed magnetic flux) a bifurcation, dependent on the input data. A major conclusion is that FRCs can exist only within a limited shape domain, i.e., combinations of plasma radius and length. These limitations reflect the requirement of equilibrium force balance and tearing stability. Inspection of a considerable range of experiments shows that the shape domain reflects actual operational boundaries. Working from timeline data from an experiment the tool finds the evolving two-dimensional structure plus the time histories of critical properties such as trapped flux, plasma energy, and plasma current. These timelines offer clues about underlying stability and transport properties not contained within the equilibrium model itself. Properties of traditional FRCs as well as modern, neutral-beam driven FRCs are explored, and specific experimental shots are reconstructed.