Development of a Simple Stellarator using Tilted Circular Toroidal Field Coils

TL;DR

This paper presents a simplified stellarator design using tilted circular coils to generate rotational transform, with magnetic surface confirmation, partial coil optimization, and favorable confinement properties demonstrated through various analyses.

Contribution

The study introduces a novel simplified stellarator configuration with tilted coils and demonstrates its magnetic surface integrity and confinement performance.

Findings

Nested magnetic flux surfaces confirmed via field-line tracing.

Optimized coil parameters reduce neoclassical transport.

Favorable confinement shown for protons and alpha particles.

Abstract

This study investigates a simplified stellarator configuration employing circular coils, in which rotational transform is generated by tilting the toroidal field (TF) coils. A pair of axisymmetric poloidal field (PF) coils is introduced to compensate for the vertical magnetic field component produced by the tilted TF coils, together forming the three-dimensional magnetic configuration. The existence of clear, nested magnetic flux surfaces is confirmed through magnetic field-line tracing, and the corresponding vacuum free-boundary equilibrium is computed using the DESC solver. The coil set is partially optimized by varying the TF coil radius and tilt angle to reduce neoclassical transport and enhance alpha-particle confinement. The optimized configuration is compared with fully optimized stellarators such as W7-X and LHD in terms of alpha-particle confinement and the Gamma_C proxy. The neoclassical transport coefficient D11 is evaluated and found to be low. Collisionless guiding-center orbit calculations for 100 eV protons and 3.5 MeV alpha particles further demonstrate favorable confinement properties.