Additively Manufactured NdFeB Polyphenylene Sulfide Halbach Magnets to Generate Variable Magnetic Fields for Neutron Reflectometry

Abstract

Halbach arrays are the most efficient closed structures for generating directed magnetic fields and gradients, and are widely used in various electric machines. We utilized fused deposition modeling-based Big Area Additive Manufacturing technology to print customized, compensated concentric Halbach array rings, using polyphenylene sulfide-bonded NdFeB permanent magnets for polarized neutron reflectometry. The Halbach rings could generate a 0 £ B £ 0.30 T field, while preserving 90% polarization of an axial neutron beam. Polarized neutron beams are used to study a wide range of structural and magnetic phenomena spanning physics, chemistry, and biology. In this study, we demonstrate the effectiveness of additive manufacturing for producing prototype Halbach arrays, characterize their magnetic properties, and generated magnetic fields, and discuss the conservation of neutron beam polarization as a function of magnetic field.

Additive Manufacturing of Hard Magnetic Passive Shims to Increase Field Homogeneity of a Halbach Magnet

“…At present, this is not possible in the printer used for this work, but it is an area of ongoing research. [ 15 ]…”

“…At present, this is not possible in the printer used for this work, but it is an area of ongoing research. [15] It should be considered that the shape optimization of the shims was only performed on an initial simple design idea by a parametric study of the scale factor. There certainly remains room for improvement through employing more advanced optimization approaches, including topology optimization or machine learning.…”

“…Halbach arrays can be exploited to focus or defocus spin‐bearing particles and splitting or merging their beams, and to generate variable magnetic fields for Neutron reflectometry. [ 15 ] Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), magnetometers, neutron interferometers, magnetic traps, and particle counters are a few of many examples where a uniform magnetic field is required. The resolution of magnetic analysis methods can be improved by generating a stronger and more homogeneous field over the region of interest (ROI).…”

“…From a materials standpoint, there has been an increased demand for hard magnets NdFeB type, in recent years. [ 15 ] Significant improvements in the properties of rare‐earth‐based high‐flux PMs have revolutionized the manufacturing of efficient and portable electrical devices; [ 37,38 ] however, current industrial scale production methods, such as injection molding, compression molding, and powder sintering, are very limited in terms of design and size flexibility of the resulting permanent magnets made from hard magnet materials. Additionally, a considerable amount of the magnetic material is wasted during the manufacturing processes.…”

3D Printing Technologies for Fabrication of Magnetic Materials Based on Metal–Polymer Composites: A Review

“…The Halbach magnetic assembly is a special configuration of permanent magnets, characterized by the fact that the magnetic field on one of its sides is almost completely absent due to the special arrangement of the assembly elements, and it is homogeneous inside. The Halbach assembly can be used to focus or defocus particles with a spin and to split or merge their beams, as well as to generate alternating magnetic fields for neutron reflectometry [59].…”