Particle beam accelerator and particle therapy system

A particle beam accelerator, comprising:

• a main magnetic field generation device including a pair of magnetic poles each having a circular outer periphery, the main magnetic field generation device generating a main magnetic field in an acceleration space between the pair of magnetic poles;
• an ion introduction device that introduces ions into the acceleration space;
• a radiofrequency acceleration system that feeds a radiofrequency electric field to the ions to accelerate the ions, forms an ion beam circulating in the acceleration space, and accelerates the ion beam to have desired energy;
• a dynamic magnetic field feed device that feeds a magnetic field at predetermined timing to a predetermined region through which the ion beam having the desired energy circulating in the acceleration space passes, and displaces a circular orbit of the ion beam having the desired energy;
• a regenerator gradient magnetic field region formed at a predetermined position in a peripheral edge portion of each of the magnetic poles;
• and
• an extraction channel arranged on an outer periphery of the magnetic pole, the extraction channel including an opening through which the ion beam having the desired energy is captured, the extraction channel guiding, from the acceleration space to an outside, the ion beam having been captured,
• wherein
• a position where the ion introduction device introduces ions into the acceleration space is a position close to the extraction channel relative to a center of the magnetic pole,
• a region to which the dynamic magnetic field feed device feeds a magnetic field is a region covering a position along a circumferential direction of the circular orbit of the ion beam having the desired energy, the position in a direction where the circular orbit is displaced,
• a gradient magnetic field that increases toward the outer periphery of the magnetic pole is formed in the regenerator gradient magnetic field region, and
• the position provided with the regenerator gradient magnetic field region is a position where the ion beam having the desired energy in the circular orbit does not pass before a magnetic field of the dynamic magnetic field feed device is fed, and an ion beam in the circular orbit displaced by feeding a magnetic field of the dynamic magnetic field feed device passes.