Patent ID: 8446054

Claim:
A periodic magnetic field generation device comprising: a field pole of a Halbach array structure in which main pole permanent magnets magnetized in a direction of a generated field and sub pole permanent magnets magnetized in a direction orthogonal to the direction of magnetic poles of the main pole permanent magnets are alternately disposed linearly so as to be adjacent to each other, wherein a part of each of the main pole permanent magnets on a side on which the magnetic field is generated is replaced by a soft magnetic member, a relation A<B is established when a length of the soft magnetic member on the side of the generated field along a moving direction of the field is A, and a length of each main pole permanent magnet on a side of a back yoke along the moving direction of the field is B, both the soft magnetic member and the main pole permanent magnets have a trapezoidal shape, and the length A of the soft magnetic member on the side of the generated field along the moving direction is equal to a length of each sub pole permanent magnet on a side of the back yoke along the moving direction.