Combination of quasi-isodynamic and piecewise omnigenous magnetic fields

TL;DR

This paper introduces QI-pwO magnetic fields that combine quasi-isodynamic and piecewise omnigenous properties, optimizing neoclassical transport while reducing flux surface shaping complexity for stellarator design.

Contribution

It proposes a novel magnetic field configuration that merges quasi-isodynamicity with piecewise omnigenity, easing the integration of transport optimization and engineering constraints.

Findings

QI-pwO fields maintain neoclassical transport properties.

They reduce flux surface shaping complexity.

Potential for easier stellarator reactor design.

Abstract

Due to their simultaneous optimization for radial and parallel neoclassical transport, quasi-isodynamic fields have been the main choice of stellarator magnetic configuration for most fusion reactor candidates in recent years. However, achieving a high degree of quasi-isodynamicity often comes at the cost of a strong shaping of the flux surfaces of the stellarator and complex coil geometries. In this work, the concepts of quasi-isodynamicity and piecewise omnigenity are combined to form QI-pwO fields. These fields are quasi-isodynamic in the low-field region of the magnetic surface, whereas they significantly depart from quasi-isodynamicity in the high-field region without sacrificing the neoclassical transport properties of quasi-isodynamic fields. This departure could make it easier to integrate the optimization of neoclassical transport with other physical and technological aspects of a stellarator reactor.