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.
Highlights
The proof of concept for generating a unidirectional magnetic field using vector addition of magnets was first demonstrated by Mallinson.[1]
In the Introduction section, we describe the Halbach array and its application to unambiguously determine the phase information in a polarized neutron reflectometry experiment
The Brem and HC values at 300°C were used in the analysis of the magnetic fields of the additive manufacturing (AM)-fabricated rings
Summary
The proof of concept for generating a unidirectional magnetic field using vector addition of magnets was first demonstrated by Mallinson.[1]. A novel prototype Halbach ring magnet has been designed for the magnetism reflectometer[32,33,34] at the Spallation Neutron Source (SNS) located at Oak Ridge National Laboratory (ORNL), using the Big Area Additive Manufacturing (BAAM) printer located at ORNL’s Material Demonstration Facility. We successfully printed NdFeB-PPS magnets and fabricated a prototype Halbach array using two nested Halbach rings and demonstrated polarization conservation using a traverse polarized neutron beam. In the Experimental Details section, the Halbach disc printing, characterization of the magnetic properties of the printed material, and the fabrication of the Halbach arrays are discussed. The magnetic properties of the printed parts were measured with the physical property measurement system (PPMS) (Quantum Design, USA), and the magnetic field and its components were measured using a Hall probe (Metrolab Three-axis Hall-magnetometer)
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