Patent ID: 7759938

Claim:
An apparatus, comprising: a yoke comprising a base, a first flange attached orthogonally to the base and having a first free end, and a second flange attached orthogonally to the base and having a second free end, the second flange spaced apart from the first flange; a first magnet pole attached to the first free end and comprising a first permanent magnet; a second magnet pole attached to the second free end and comprising a second permanent magnet, the first magnet pole and the second magnet pole defining an air gap therebetween, and the first magnet pole and the second magnet pole configured to generate a static magnetic field having a uniform magnetic field distribution and a static magnetic field strength in the air gap; and a first magnetic field adjusting member comprising a first substrate and a first plurality of field control rods coupled to a face of the first substrate.