Circular accelerator and operating method therefor

A circular accelerator that accelerates charged particles injected into the center thereof by a radio-frequency electric field while making the particles orbit along a spiral orbit by a bending magnetic field, the circular accelerator comprising:

• a bending electromagnet that is excited by an exciting coil and thereby generates the bending magnetic field, the bending electromagnet including an electromagnet hill for forming a narrow magnetic pole gap and an electromagnet valley for forming a wide magnetic pole gap alternately disposed in an orbiting directing of the charged particles;
• a radio-frequency power source that generates the radio-frequency electric field in accordance with an orbital frequency of the charged particles;
• a radio-frequency electromagnetic field coupling part connected to the radio-frequency power source;
• an acceleration electrode connected to the radio-frequency electromagnetic field coupling part;
• and
• an acceleration-electrode-opposing ground plate provided to form an acceleration gap between the plate itself and the acceleration electrode, for generating the radio-frequency electromagnetic field in the orbiting direction of the charged particles;
• wherein
• average magnetic flux density B(r) in the orbiting direction of the charged particles and total energy of the particles E(r) in a position with a radius r can be expressed using average magnetic flux density BO at a radius corresponding to an extraction position of the charged particles and energy EO of the particles in the extraction position as follows:
• B(r)=(BO/EOx)×E(r)x
• in which relationship, the bending electromagnet generates magnetic flux density distribution with x being a constant excluding 1.