The "shim-a-ring" magnet: Configurable static magnetic fields using a ring magnet with a concentric ferromagnetic shim

Abstract

We introduce a permanent magnet assembly that can be configured to obtain uniform, gradient, or tunable field distribution. The design is composed of a single ring shaped permanent magnet and a concentric ferromagnetic shim. Magnetic field is configured by changing the shape of the air gap inside the ring magnet. Circular cross-section produces up to 0.54 T uniform field, whereas rectangular or triangular cross-sections result in gradient magnetic field distributions. Tunable field from a given ring magnet is obtained by changing the thickness of the ferromagnetic shim or the spacing between the shim and the permanent magnet. © 2013 AIP Publishing LLC.