Reactor-scale stellarators with force and torque minimized dipole coils

TL;DR

This paper introduces a novel coil optimization method for stellarators that minimizes force and torque, enabling large-scale design of planar dipole coil arrays for reactor-scale magnetic confinement devices.

Contribution

It presents the first large-scale optimization of planar dipole coil arrays for stellarators using autodifferentiation with force and torque minimization objectives.

Findings

Minimizing coil orientation and location reduces forces and torques.

Optimized coil configurations achieve tolerable field errors.

Solutions for three reactor-scale quasi-symmetric stellarators are provided.

Abstract

In this work, we utilize new coil objectives for stellarator optimization with autodifferentiation, including pointwise and net coil-coil forces and torques. We use these methods to perform the first large-scale optimization of planar dipole coil arrays, since arrays of small and geometrically simple coils have been proposed to partially produce the 3D magnetic fields for stellarators, generate advantageous magnetic field perturbations in tokamaks, and provide active, real-time control capabilities. We perform an ablation study to show that minimizing the orientation and location of each coil may be essential to get coil forces, coil torques, and field errors to tolerable levels. We conclude with solutions for three reactor-scale quasi-symmetric stellarators by jointly optimizing nonplanar TF coils and planar coil arrays.