Opposed magnet-type magnetic circuit assembly with permanent magnets

摘要

The invention relates to a opposed-magnet magnetic circuit assembly with permanent magnets for generating a magnetic field of high uniformity for magnetic resonance, the assembly comprising a pair of permanent magnets (111,114) each having the form of a circular or elliptic plate, of which the aspect ratio is in the range from 0.5 to 2, the pair of permanent magnets oppositely facing up and down each to the other keeping a magnetic field gap space there between, a pair of field adjustment plates (112,113) each mounted on the surface of a respective one of the permanent magnets to face the magnetic field gap space, a pair of back yokes (110,115) each having the form of a generally polygonal plate having at least six corners and each mounted on the surface of the permanent magnet opposite to the magnetic field gap space, and two and only two connecting yokes oppositely facing each to the other and magnetically connecting the back yokes to form a closed magnetic circuit, the magnetic circuit assembly comprising: a) a pair; i.e. two, upper and lower back yokes, and two and only two columnar yokes, each of which being connected to the upper end and lower end, respectively, thereof, b) each of the columnar yokes being an integral body from the up to down direction, the cross section of each of the columnar yokes being square or rectangular, c) the cross section of each of the columnar yokes being smaller than the cross section in the upper and lower end portions thereof, d) the inward surface of each of the columnar yokes (108,109) facing the magnetic field gap (116) forming a surface having a straight generating line.