Electron root optimisation for stellarator reactor designs

TL;DR

This paper presents an optimization method for stellarator reactors to promote electron root solutions of the radial electric field, enhancing confinement and impurity control in fusion devices.

Contribution

It introduces a novel optimization approach targeting electron root solutions in quasi-isodynamic stellarators, applicable to both vacuum and finite pressure conditions.

Findings

Electron root optimization is feasible in quasi-isodynamic stellarators.

Optimized configurations improve impurity control and confinement.

Potential reduction in turbulence through targeted electric field solutions.

Abstract

In this work, we propose a method of optimising stellarator devices to favour the presence of an electron root solution of the radial electric field. Such a solution can help avoid heavy impurity accumulation, improve neoclassical thermal ion confinement and helium ash exhaust and possibly reduce turbulence. This study shows that an optimisation for such a root is possible in quasi-isodynamic stellarators. Examples are shown for both vacuum and finite plasma pressure configurations.