Simplified magnet design and manufacture based on patterning of wide conductors

TL;DR

This paper presents a novel simplified design and manufacturing method for high-temperature superconducting magnets using patterning of wide conductors, validated through prototypes for gyrotron and MRI applications with high precision.

Contribution

It introduces a new technique for magnet design using grooving patterns and inverse problem solving, streamlining fabrication and assembly of superconducting magnets.

Findings

Gyrotron magnet replicated with 10$^{-1}$ magnetic field accuracy.

MRI magnet achieved about 50 ppm field uniformity.

Validated the patterning approach for complex magnetic field configurations.

Abstract

The fabrication and assembly of High Temperature Superconducting (HTS) magnets can be significantly streamlined by (1) direct deposition of HTS onto modular components and (2) laser-ablated grooves to bound and guide the electric currents over the superconducting surfaces. "Coils" bounded by consecutive grooves can be individually powered, or connected in series, or in parallel. Applications include plasma-confinement devices such as stellarators and magnets for particle accelerators. On the way to HTS magnets generating more complicated three-dimensional fields, this paper validates the technique for two cylindrically symmetric magnets made of standard conductors. The optimized grooving pattern is considered as an inverse problem that is resolved using a least squares approach with Tikhonov regularization. This approach was first applied to design a magnet that replicates the magnetic field configuration of a microwave source of the gyrotron type. Gyrotrons require a particular profile of magnetic field, which our aluminium prototype successfully reproduced with 10$^{-1}$ precision. The second one, in copper, is a small-size, reduced-field magnet for Magnetic Resonance Imaging (MRI). This application requires highly uniform longitudinal fields. The achieved precision (about 50 ppm) is exceptional for an MRI magnet just getting out of the factory, and can easily meet hospital standards after minimal shimming or other error field correction. Future work and other potential applications of wide, patterned conductors or superconductors are also discussed.