Magnet assemblies for producing highly homogeneous magnetic fields

Claim 1

A MAGNET ASSEMBLY COMPRISING TWO POLE PIECES OF MAGNETICALLY SOFT MATERIAL EACH HAVING A CONTINUOUS PLANE POLE FACE, SAID POLE PIECES BEING ARRANGED SUCH THAT SAID POLE FACES ARE DISPOSED IN DIRECT FACE-TO-FACE RELATIONSHIP IN SPACED SUBSTANTIALLY PARALLEL PLANES AND HAVING TWO AXES OF SYMMETRY EXTENDING AT RIGHT-ANGLES TO ONE ANOTHER PARALLEL TO SAID PLANES CONTAINING THE POLE FACES, AND MAGNETIC FLUX-PROVIDING MEANS ARRANGED BETWEEN SAID POLE FACES AND SYMMETRICALLY WITH RESPECT TO SAID AXES TO DEFINE WITH SAID POLE FACES THE BOUNDARIES OF AN AIR GAP BETWEEN SAID POLE PIECES, SAID FLUX-PROVIDING MEANS BEING DISCONTINUOUS AT TWO OPPOSITELY DISPOSED LOCATIONS THROUGH WHICH ONE OF THE SAID AXES EXTENDS AND BEING POLED SO AS TO RENDER THE OPPOSED POLE PIECES OF OPPOSITE POLARITY, AND SAID POLE PIECES BEING OF A THICKNESS IN A DIRECTION PERPENDICULAR TO SAID PLANES SUCH THAT THE RELUCTANCE OF THE POLE PIECES IS SMALL COMPARED WITH THE RELUCTANCE OF THE MAGNETIC PATH THROUGH SAID FLUX-PROVIDING MEANS, WHEREBY A MAGNETIC FIELD OF HIGH HOMOGENEITY IS PRODUCED WITHIN SAID AIR GAP IN THE DIRECTIONS OF BOTH SAID AXES.