Patent ID: 7772577

Claim:
A particle beam therapy system comprising: a synchrotron for accelerating a charged particle beam by means of a radio frequency acceleration voltage applied to an acceleration cavity such that the charged particle beam has a predetermined energy level, causing the charged particle beam to exceed a stability limit by means of a radio frequency electromagnetic field applied to an extraction device, and then extracting the thus-prepared charged particle beam; a beam transport system for introducing the charged particle beam extracted from said synchrotron to a treatment room; an irradiation system for irradiating an affected area of a patient with the charged particle beam in conformity with the shape of the affected area in the treatment room; and a controller for turning on the radio frequency electromagnetic field to be applied to the extraction device when the charged particle beam is to be supplied to said irradiation system, turning off the radio frequency electromagnetic field to be applied to the extraction device when the supply of the charged particle beam to said irradiation system is to be blocked by means of an electromagnet provided in said beam transport system or in said synchrotron, and turning off the radio frequency acceleration voltage to be applied to the acceleration cavity in synchronization with the turning-off of the radio frequency electromagnetic field to be applied to the extraction device.