LOW-LEAKAGE MAGNETIC-FIELD MAGNET AND SHIELD COIL ASSEMBLY

摘要

A magnet device provided with a shield current carrying means in which two sets of magneto-static field generating source for generating magnetic fields directed towards a first direction are disposed facing each other across a finite region and at least one set of the magneto-static field generating sources are disclosed on at least two almost concentric circles, wherein, on a first plane including a first axis , a second axis and a first point, the first point being a point of insertion between the first axis parallel to the first direction and passing the almost center of the shield current carrying means and the second axis crossing at right angles the first axis and spaced almost equal distance from the two sets of the generating sources, positive and negative current carrying directions of one set out of two sets of magneto-static field generating sources or those in respective sets are arranged alternately, when an angle formed by a half line at the n-th point position from the first point to extend toward the geometric center of a section of the shield current carrying means and the first axis is &thetas;n, and the current carrying directions of the shield current carrying means are set in the order of increasing &thetas;n.