| 摘要 |
Provided is an accelerator allowing ion beams having different energies to be emitted efficiently. The accelerator has a circular vacuum container comprising a pair of circular return yokes facing one another. An injection electrode 18 is disposed more toward the entrance side of a beam ejection path within the return yokes than the central axis of the vacuum container. Inside the return yokes, six magnetic poles are disposed radially from the injection electrode 18 in the surroundings of the injection electrode 18. Six concave portions are disposed so as to alternate with each of the magnetic poles in the circumferential direction of the return yokes. Formed inside the vacuum container are a trajectory concentric region, where a plurality of beam revolution trajectories 78 centered around the injection electrode 18 exist, and in the periphery of this region, a trajectory off-centered region, where a plurality of beam revolution trajectories off-centered from the injection electrode 18 exist. In the trajectory off-centered region, the beam revolution trajectories 78 become dense between the injection electrode 18 and the entrance of the beam ejection path, and, with the injection electrode 18 serving as the base point, on the side that is 180° opposite to the entrance of the beam ejection path, the intervals between the beam revolution trajectories 78 become wider. |
