| 摘要 |
Apparatus and method for the adjustment of a magnetic field produced by permanent magnet arrangements (68, 70) facing each other across an air gap (72) include a series of ferromagnetic shim blocks individually adjustably positioned within the magnet arrangements to adjust the strength and uniformity of the magnetic field. A backing plate (76, 90) to which the permanent magnets are attached has channels within which adjusting elements are used to move the shim blocks with relation to the permanent magnets, preferably toward or away from the air gap. Shim blocks are arranged in selected geometric arrays and shapes responsive to the geometry of the magnet arrangements and may be formed as a toroidal shapes or as individual blocks of varying sizes.
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