Scanning electromagnet control system, scanning electromagnet control method, and particle beam therapy system

A scanning electromagnet control method performed by a scanning electromagnet control system for controlling a scanning electromagnet that causes magnetic fields generated by a plurality of systems of windings whose one ends are connected to each other to act on a charged particle beam to deflect the charged particle beam, the scanning electromagnet control method comprising:

• applying a constant voltage to each of the other ends of the windings of the scanning electromagnet when a direction of the charged particle beam is fixed, the constant voltage corresponding to the direction of the charged particle beam;
• and
• applying a varying voltage to each of the other ends of the windings when the direction of the charged particle beam is changed, the varying voltage causing a potential difference between the other ends of the windings to be larger than potential differences before and after the change of the direction.

A particle beam therapy system including an accelerator that extracts a charged particle beam, a transport device that transports the charged particle beam extracted from the accelerator, and an irradiation nozzle that irradiates a patient with the charged particle beam transported by the transport device, the particle beam therapy system comprising:

• a scanning electromagnet provided in at least one of the accelerator, the transport device, and the irradiation nozzle to cause magnetic fields generated by a plurality of systems of windings whose one ends are connected to each other to act on the charged particle beam to deflect the charged particle beam;
• and
• a scanning electromagnet control system that applies a constant voltage to each of the other ends of the windings of the scanning electromagnet when a direction of the charged particle beam is fixed, the constant voltage corresponding to the direction of the charged particle beam, and applies a varying voltage to each of the other ends of the windings when the direction of the charged particle beam is changed, the varying voltage causing a potential difference between the other ends of the windings to be larger than potential differences before and after the change of the direction.