Manufacturing Tolerances of Non-Planar Coils for an Optimized Tabletop Stellarator

TL;DR

This paper investigates manufacturing deviations of non-planar stellarator coils using 3D scans, revealing that CNC-machined coils have significantly lower deviations than 3D-printed ones, which impacts magnetic field accuracy and assembly quality.

Contribution

It provides a detailed analysis of manufacturing tolerances for different coil fabrication methods and models deviations using Gaussian processes to inform stellarator design.

Findings

CNC-machined coils exhibit nearly ten times lower deviations than 3D-printed coils.

Manufacturing deviations significantly affect magnetic field precision.

High fabrication accuracy enables improved stellarator performance.

Abstract

Stellarator coils are known for their complexity and departure from planarity, along with tight manufacturing tolerances in order to achieve the target magnetic field accuracy. These requirements can lead to increased costs and delays in assembly; failure to meet them can compromise the stellarator's performance. Small-scale experiments offer opportunities to develop and benchmark stellarator coil design and evaluation methods more quickly and at lower budget. In this work, we analyze precise 3D scans of the manufacturing deviations of two 3D-printed coil frames (steel, Ti alloy) and one CNC-machined coil frame (Al alloy), as part of assessing these approaches to fabricating high-temperature superconducting (HTS) coils for a tabletop stellarator. The deviations are measured along the coil length, then modeled using Gaussian processes to extract characteristic length scales. Finally a statistical study of field accuracy is performed using relevant experimental parameters. We conclude that the manufacturing perturbations along the winding path from CNC-machining are almost an order of magnitude lower than those from Additive Manufacturing. Together with high overall fabrication accuracy, this allows for higher magnetic field precision and an improved assembly process.