Patent ID: 6504462
Filing Date: 2003-01-07
Classification: G01R,H01F,Y10T

Abstract:
An apparatus for changing homogeneity of a magnetic field produced by a magnet having a pole face, comprising:a shim, in the form of one of a ring and an arcuate element, having a mass; and a plate, having a substantially flat face and including at least one fastener opening for accommodating a fastener by which the plate can be removably attached to the magnet pole face, and a groove in the substantially flat face that holds the shim in place such that the shim is disposed in a selectable location with respect to the plate and the magnet pole face, when the plate is attached to the magnet pole face, wherein the groove has a depth that is shallower than a thickness of the plate at a location of the plate where the groove is disposed; and wherein the shim mass and the selectable location together correspond to a magnitude change of a term selected from among any harmonic terms of a polynomial expansion describing the magnetic field in order to change the homogeneity of the magnetic field, when the plate is attached to the magnet pole face.