Stochastic single-stage stellarator optimization using fixed-boundary equilibria

TL;DR

This paper introduces a stochastic single-stage optimization method for stellarators that enhances robustness and configuration quality by integrating coil perturbations with fixed-boundary plasma equilibrium calculations.

Contribution

The paper presents a novel stochastic single-stage optimization approach combining coil and plasma boundary optimization, improving stellarator design robustness over traditional deterministic methods.

Findings

Improved squared flux and quasisymmetry in optimized configurations

Enhanced robustness against coil perturbations

Comparison shows superiority over standard stochastic and single-stage methods

Abstract

In this paper, single-stage stellarator optimization is combined with stochastic coil optimization to improve the robustness of the stellarator as compared to deterministic methods. The plasma boundary, solved with an MHD solver in fixed-boundary mode, is linked to a set of randomly perturbed coils via the squared flux. The optimizer avoids sharp local minima and can reach improved configurations. Two different configurations obtained with our method, one quasi-axisymmetric and one quasi-helically symmetric, are compared against both the standard stochastic stage II method and the single-stage method. The new configurations shown here yield improved squared flux, quasisymmetry, and particle loss following a posteriori perturbation of the coils.