Circular accelerator and particle beam treatment system

Abstract

There is provide a circular accelerator and a particle beam therapy system that can improve the beam extraction efficiency. A circular accelerator that accelerates and extracts charged particle beams circulating in a magnetic field includes a first magnetic field region in which closed trajectories of the beams with different energies are eccentric and which has a magnetic field gradient decreasing in the magnetic field toward an outer peripheral side and a second magnetic field region having a magnetic field gradient increasing in the magnetic field toward the outer peripheral side. A border between the first magnetic field region and the second magnetic field region is located on a downstream side in a traveling direction of the beam with respect to a predetermined region in which an interval between the closed trajectories of the beams with the different energies is narrowest.

Dependencies are inferred from the claim text.