Enhancing Stellarator Accessibility through Port Size Optimization

TL;DR

This paper presents a new optimization method for stellarator design that improves access port size without compromising magnetic field quality, using Pareto front analysis and coil shaping techniques.

Contribution

It introduces a novel optimization approach explicitly targeting access port size in stellarators, incorporating coil shaping and Pareto analysis.

Findings

Optimized port locations enhance access without degrading magnetic field quality.

Additional shaping coils can surpass previous design limitations.

Pareto front analysis reveals trade-offs between port size and magnetic performance.

Abstract

Access to the plasma chamber in a stellarator reactor is essential for maintenance and diagnostics. However, the complex geometry of stellarator coils, often characterized by their strong twisting, can severely limit the space available for access ports. This study introduces a novel optimization approach in which access ports are represented as closed curves on the plasma boundary. By carefully selecting a set of objectives and penalties related to the access port, we demonstrate the first stellarator coil optimization explicitly targeting improved access port size. The trade-off between magnetic field quality and port size is analyzed through the Pareto front of their respective objectives. The optimal location of a port is explained using a current potential approach. Finally, we show that additional shaping coils, such as windowpane coils, can enable the crossing of the Pareto front to achieve superior configurations.