A neutron source for medical therapy purposes comprising a cyclotron comprising an iron metal housing acting as a magnetic yoke, magnetic shield, radiation shield, and vacuum vessel, a pair of superconducting coils mounted in a cavity in the housing said coils being cooled to superconducting temperatures by passage of a refrigerant fluid therethrough and connected to an electrical energy source such that a high current flows in the coils producing an intense magnetic field inwardly between the coils, an ion orbiting region defined by pairs of sectoral-shaped RF electrode structures energized at an RF frequency and focussing flutter poles mounted in the intense magnetic field between coils, a source of ions positioned centrally of the ion orbiting region to provide a stream of ions that will be orbited in the orbit region; an ion target positioned internally of said iron housing at an outer position in the orbit region such that orbiting ions strike the target and produce neutrons; a channel formed in the iron housing from the target to the exterior for passage of the beam of neutrons formed at the target, said channel acting as a beam collimator; and a mounting structure for movably mounting the cyclotron and target such that the neutron beam produced can be employed at more than one position.