Permanent magnet spheres: Design, construction, and application (invited)

Abstract

A summary of the salutary properties of the strong permanent magnet field sources known as magic spheres is given. Topics of discussion include: obtainable field strengths, field uniformity, field insensitivity to structural modifications, methods of avoidance of field distortions due to access holes, tapering of field strength with progression along the field axis, field augmentation in different working space geometries, simplified manufacture of the magic spheres, and potential employment for various purposes. Field measurements made on a recently completed prototypical augmented magic sphere for a microwave radiation source are reported and compared with theory.