Patent ID: 8476602

Claim:
A magnet used in an ion beam irradiation apparatus, the magnet comprising: a pair of magnetic poles arranged facing each other on an inner side of the magnet across an ion beam; a plurality of magnetic field concentrating members, each of the plurality of magnetic field concentrating members comprising magnets, that are arranged on each of the opposing surfaces of the magnetic poles and that perform a function of reflecting electrons between the magnetic poles; and a protective member that covers opposing surfaces of the magnetic field concentrating members, wherein the protective member comprises a single protective member that is integrally formed over all of the magnetic field concentrating members, and further wherein a direction of a magnetic field generated by the pair of the magnetic poles is substantially the same as a direction of a magnetic field generated by the magnetic field concentrating members, between the magnetic poles, and the poles of the each of the magnetic field concentrating members are commonly oriented in the direction of the magnetic field generated by the pair of the magnetic poles.