Patent ID: 6909348

Claim:
A magnet device comprising two magnetostatic field-generating sources opposed across a finite region for generating a magnetic field in a first direction in said finite region, at least one of said generating sources including at least two shield current carrying means in almost concentric relation, said magnet device defining: a first axis being parallel to said first direction and passing through the almost center of said shield current carrying means; a second axis intersecting at right angles with said first axis and being spaced at an almost equal distance from said two magnetostatic field-generating sources; a first point where said first axis and second axis intersect, a first plane including said first axis, second axis, and first point; and an angle θn for the n-th shield current carrying means, said angle θn being in said first plane between said first axis and a half line extending from said first point to the cross section geometric center of said n-th shield current carrying means, wherein, said shield current carrying means in one or two of said magnetostatic field-generating sources have alternately positive and negative current carrying directions with increasing value of said θn.