Patent ID: 8231767

Claim:
A magnetic field generating apparatus which generates a cusped magnetic field on an electrode, the apparatus comprising: a magnet mechanism which is attached to the electrode and includes a plurality of magnets held on a holding plate; and a rotation mechanism which rotates the holding plate, wherein the plurality of magnets are arranged at grid points of a regular polygonal grid, and arrayed to be point-symmetrical about a center of a unit grid of the regular polygonal grid, a center of rotation of the holding plate by said rotation mechanism falls within the unit grid, and is at a position shifted from the center of the unit grid, the regular polygonal grid comprises a square grid, and the center of rotation is at a barycenter of one of eight right-angled isosceles triangles having, as a hypotenuse, a side that connects the center of a unit grid of the square grid and one grid point of the unit grid.