CHARGED PARTICLE BEAM RADIATION SYSTEM, SYNCHROTRON, AND BEAM EJECTION METHOD THEREFOR

摘要

When controlling the ejection of a charged particle beam from a synchrotron, a radiofrequency voltage is applied, which serves as the radio-frequency voltage to be applied to an ejection radio-frequency electrode equipping the synchrotron, and which is constituted by a first radio-frequency voltage for increasing an oscillation amplitude in such a way as to exceed a stable limit in order to eject to the exterior of the synchrotron a beam that circles inside the synchrotron, and a second radio-frequency voltage for preferentially ejecting a charged particle beam that circles in the vicinity of the stable limit, with the amplitude value of the second radio-frequency voltage being controlled in such a way that the amplitude value is 0 prior to the beam ejection start, the amplitude value increases gradually from the beam ejection start, and, once a predetermined amplitude value has been reached, this value is maintained.

主权项

1. A charged particle beam irradiation system comprising:
a synchrotron that accelerates and extracts a charged particle beam; an irradiation system that performs irradiation with the charged particle beam extracted from the synchrotron; and an extraction control apparatus that extracts a beam orbiting inside the synchrotron to the outside of the synchrotron, wherein the extraction control apparatus includes a first RF voltage output circuit that outputs a first RF voltage for increasing an oscillation amplitude of the beam so that the beam orbiting inside the synchrotron exceeds a stability limit; a second RF voltage output circuit that outputs a second RF voltage for preferentially extracting a charged particle beam orbiting around the stability limit; a combiner that combines the first RF voltage output from the first RF voltage output circuit with the second RF voltage output from the second RF voltage output circuit, and outputs a combined voltage; a RF amplifier circuit that amplifies a RF voltage output from the combiner; and a RF electrode to which the RF voltage amplified by the RF amplifier circuit is fed, wherein an amplitude of the first RF voltage is controlled depending on a current of the charged particle beam output from the synchrotron, and wherein an amplitude of the second RF voltage is set to 0 before starting of beam extraction, and the amplitude of the second RF voltage is gradually increased at the same time as starting of beam extraction, and is maintained after reaching a predetermined amplitude.