Exploration of the parameter space of piecewise omnigenous stellarator magnetic fields

TL;DR

This paper systematically characterizes and parametrizes piecewise omnigenous stellarator magnetic fields, offering a new approach to optimize stellarator designs with potential benefits for reactor development.

Contribution

It introduces a systematic method to characterize and parametrize piecewise omnigenous fields, enabling their inclusion in stellarator optimization processes.

Findings

Piecewise omnigenous fields are distinct from traditional omnigenous fields.

A systematic parametrization of piecewise omnigenous fields is developed.

This work paves the way for their use in stellarator reactor design.

Abstract

Piecewise omnigenous fields are stellarator magnetic fields that are optimized with respect to radial neoclassical transport thanks to a second adiabatic invariant that is piecewisely constant on the flux-surface. They are qualitatively different from omnigenous fields (including quasi-isodynamic or quasisymmetric fields), for which the second adiabatic invariant is a flux-surface constant. Piecewise omnigenous fields thus open an alternative path towards stellarator reactors. In this work, piecewise omnigenous fields are characterized and parametrized in a systematic manner. This is a step towards including piecewise omnigenity as an explicit design criterion in stellarator optimization, and towards a systematic study of the properties of nearly piecewise omnigenous stellarator configurations.