Piecewise omnigenous stellarators

TL;DR

This paper introduces a new family of optimized stellarator magnetic fields that combine tokamak-like energy confinement with the ability for particles to transition between different magnetic wells, expanding design possibilities.

Contribution

It presents a novel class of omnigenous stellarator configurations that allow particle transitions, overcoming previous topological constraints and broadening the design space for fusion reactors.

Findings

New family of magnetic fields with tokamak-like transport

Configurations permit particle transitions between magnetic wells

Broadened design space for stellarator optimization

Abstract

In omnigeneous magnetic fields, charged particles are perfectly confined in the absence of collisions and turbulence. For this reason, the magnetic configuration is optimized to be close to omnigenity in any candidate for a stellarator fusion reactor. However, approaching omnigenity imposes severe constraints on the spatial variation of the magnetic field. In particular, the topology of the contours of constant magnetic-field-strength on each magnetic surface must be such that there are no particles transitioning between different types of wells. This, in turn, usually leads to complicated plasma shapes and coils. This Letter presents a new family of optimized fields that display tokamak-like collisional energy transport while having transitioning particles. This result radically broadens the space of accessible reactor-relevant configurations.