A programmable stellarator-tokamak hybrid for million-scale magnetic-configuration discovery

TL;DR

This paper introduces a programmable hybrid device combining tokamak and stellarator features, using simple coils to rapidly explore over 1.66 million magnetic configurations for fusion research.

Contribution

It presents a novel hybrid design with a fixed coil set that can generate a vast space of magnetic configurations without hardware changes.

Findings

Configurations exhibit nested magnetic surfaces and low neoclassical transport.

Device can generate over 1.66 million configurations spanning various symmetries.

Configurations show favorable energetic-particle confinement.

Abstract

Tokamaks and stellarators are the leading magnetic-confinement concepts for fusion, but they rely on complementary design principles. Tokamaks use simple axisymmetric coils and plasma current, whereas stellarators use externally generated three-dimensional fields for steady-state operation. Here, we propose a programmable stellarator--tokamak hybrid that uses a fixed set of simple planar coils to access a broad magnetic-configuration space. The device adds 288 dipole-field coils to a tokamak-like coil set, with only six independent coil geometries required by symmetry. By programming coil currents, the same hardware generates more than 1.66 million optimized stellarator configurations spanning quasi-axisymmetry, quasi-helical symmetry, and quasi-isodynamicity, as well as tokamak-relevant three-dimensional perturbations. Representative configurations exhibit nested magnetic surfaces, low neoclassical transport, and favorable energetic-particle confinement. This approach enables rapid magnetic-configuration discovery without hardware redesign.