| 摘要 |
PURPOSE:To obtain a uniform distribution of a magnetic field in a prescribed region, by forming central and peripheral parts of each main pole piece more thickly than its intermediate part and besides by forming this intermediate part in such thickness that the essentially uniform distribution of the magnetic field is obtained perpendicularly to an axis in the prescribed region. CONSTITUTION:Yokes 4 are disposed on the periphery of a pair of permanent magnets 2, and pole braces 8 are used to magnetically couple both yokes 4, 4, and a main pole piece 5 is fitted to an inner periphery of each permanent magnet so as to form a magnetic circuit. Thereupon, a magnetic field is generated axially in the permanent magnet 2 in a measurement part 3a which exists in the central part of a space 3. A central part 5a of each main pole piece 5 is formed thickly, and its peripheral part 5c is formed in a step projecting shape so that a magnetic flux generated from the permanent magnet can be effectively concentrated at the part 3a of the space 3 where a specimen is measured. An intermediate part 5b between the central part 5a and the peripheral part 5c is formed essentially uniform in thickness (t) over the whole. When the thickness (t) of this intermediate part is made appropriate, uniformity in intensity and distribution of magnetic field can be obtained in a prescribed region of a space.
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