| 摘要 |
PURPOSE: To enable accurate elimination of leaked magnetic field by setting a main coil and a connection coil on a shield coil to eliminate a magnetic field formed outside an external cylinder. CONSTITUTION: A main coil 11 which has a finger-print shaped current distribution having a static magnetic field generation current as a main part is attached on an inner cylinder of a double cylinder and a shield coil 12 having a current distribution attached on an outer cylinder of the double cylinder. A connection coil 13 is connected between a cut point of a part from which a current return wire of the main coil 11 is removed and the shield coil 12. The shield coil 12 is set for such a current distribution that allows a magnetic field making a current distribution of the main coil 11 and the connection coil 13 to be reduced almost to zero outside. This enables lowering of a leaked magnetic field significantly thereby minimizing a torque.
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