Optimization and improvement of Halbach cylinder design

TL;DR

This paper conducts a comprehensive parameter survey of a 16-segment Halbach cylinder, optimizing design parameters for magnetic performance and exploring enhancements for magnetic cooling applications.

Contribution

It introduces an optimized design methodology for Halbach cylinders, including the effects of added magnet blocks and application-specific parameters for magnetic cooling.

Findings

Optimal external radius and length minimize magnet volume for given flux density.

Adding magnet blocks on end faces increases flux density and homogeneity.

Longer cylinders with smaller external radius are best for magnetic cooling efficiency.

Abstract

In this paper we describe the results of a parameter survey of a 16 segmented Halbach cylinder in three dimensions in which the parameters internal radius, $r_{\mathrm{\scriptsize{in}}}$, external radius, $r_{\mathrm{\scriptsize{ex}}}$, and length, $L$, have been varied. Optimal values of $r_{\mathrm{\scriptsize{ex}}}$ and $L$ were found for a Halbach cylinder with the least possible volume of magnets with a given mean flux density in the cylinder bore. The volume of the cylinder bore could also be significantly increase by only slightly increasing the volume of the magnets, for a fixed mean flux density. Placing additional blocks of magnets on the end faces of the Halbach cylinder also improved the mean flux density in the cylinder bore, especially so for short Halbach cylinders with large $r_{\mathrm{\scriptsize{ex}}}$. Moreover magnetic cooling as an application for Halbach cylinders was considered. A magnetic cooling quality parameter, $\Lambda_{\mathrm{cool}}$, was introduced and results showed that this parameter was optimal for long Halbach cylinders with small $r_{\mathrm{\scriptsize{ex}}}$. Using the previously mentioned additional blocks of magnets can improve the parameter by as much as 15% as well as improve the homogeneity of the field in the cylinder bore.