Hitachi, Ltd.

Shigemitsu Hara

Masumi Umezawa

Hideaki Nishiuchi

Takayoshi Seki

Takamichi Aoki

Fuutarou Ebina

Kensuke Amemiya

Kazuo Hiramoto

Futaro Ebina

Masanobu Tanaka

Ion beams are efficiently extracted with an accelerator that includes a circular vacuum container including a pair of circular return yokes facing each other. Six magnetic poles are radially disposed from the injection electrode at the periphery thereof in the return yoke. Six recessions are disposed alternately with the respective magnetic poles in the circumferential direction of the return yoke. In the vacuum container, a concentric trajectory region, in which multiple beam turning trajectories centered around the injection electrode are present, is formed, and an eccentric trajectory region, in which multiple beam turning trajectories eccentric from the injection electrode are present, is formed around the region. In the eccentric trajectory region, the beam turning trajectories are dense between the injection electrode and the inlet of the beam extraction path. Gaps between the beam turning trajectories are wide in a direction 180&#xb0; opposite to the inlet of the beam extraction path.

Accelerator and particle beam irradiation system

An acceleratorincludes a circular vacuum container including circular return yokesA,B. An injection electrodeis disposed closer to an inlet of a beam extraction pathin the return yokeB than a central axis C of the vacuum container. Magnetic polesA toF are radially disposed from the injection electrodeat the periphery of the injection electrodein the return yokeB. RecessionsA toF are disposed alternately with the magnetic polesA toF in the circumferential direction of the return yokeB. In the vacuum container, a concentric trajectory region, in which multiple beam turning trajectories centered around the injection electrodeare present, is formed, and an eccentric trajectory region, in which multiple beam turning trajectories eccentric from the injection electrodeare present, is formed around the region.

The accelerator includes a circular vacuum container which contains a circular return yoke. With respect to the central axis of the vacuum container, an incidence electrode is arranged towards the entrance of a beam emission path inside of the return yoke. Inside of the return yoke, electrodes are arranged radially from the incidence electrode in the periphery of the incidence electrode. Recesses are arranged alternately with the electrodes in the circumferential direction of the return yoke. In the vacuum container, an orbit-concentric region is formed in which multiple beam orbits centered on the incidence electrode are present, and, in the periphery of said region, an orbit-eccentric area is formed in which multiple beam orbits eccentric to the incidence electrode are present. In the orbit-eccentric region, the beam orbits between the incidence electrode and the entrance to the beam emission path are denser.

Accelerator system and medical accelerator facility

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Tokyo, Japan

Shigemitsu Hara