Patent Number: 
Section: claims

1. A particle beam therapy system comprising:a beam energy changing unit that changes the energy of an incident particle beam;a beam energy change control unit that outputs a command for controlling the beam energy changing unit;an irradiation unit that irradiates a particle beam exiting from the beam energy changing unit onto an irradiation subject; andan irradiation control unit that outputs a command for controlling the energy and position of a particle beam to be irradiated onto the irradiation subject,wherein the beam energy changing unit includes deflection electromagnets that sequentially deflect the incident particle beam into a plurality of intra-apparatus beam orbits, a plurality of separate variable energy attenuation units disposed in the respective intra-apparatus beam orbits, and a deflection electromagnet that performs deflection in such a way that particle beams that pass through the respective variable energy attenuation units fall into a single and the same orbit; and while a particle beam passes through one of the variable energy attenuation units, the beam energy change control unit performs control in such a way as to change the energy attenuation amount of at least one of the other variable energy attenuation units, based on the command from the irradiation control unit, each variable energy attenuation unit configured to change the energy attenuation amount without changing energy attenuation amounts of other variable energy attenuation units or a path of the particle beam passing through the variable energy attenuation unit. 2. The particle beam therapy system according to claim 1, wherein the intra-apparatus beam orbits have portions that are in parallel with one another, and the variable energy attenuation units are provided in the respective parallel portions. 3. The particle beam therapy system according to claim 1, wherein the number of the intra-apparatus beam orbits is two. 4. The particle beam therapy system according to claim 1, wherein the number of the intra-apparatus beam orbits is three. 5. The particle beam therapy system according to claim 1, wherein the variable energy attenuation unit is configured in such a way as to be provided with a water introducing tube for introducing water into a shape-variable container whose side faces are formed of a shape-variable material, in such a manner that the pressure of water can be controlled, and in such a way that the thickness of a portion, of the shape-variable container, through which a particle beam passes can be changed by changing the pressure of water. 6. The particle beam therapy system according to claim 1, wherein the variable energy attenuation unit is configured in such a way as to be provided with a particle beam energy attenuator whose thickness changes in a single direction and as to be provided in such a manner that the single direction in which the thickness of the particle beam energy attenuator changes is slanted at a predetermined angle from a plane including a plurality of intra-apparatus beam orbits, and in such a way that an energy attenuation amount is changed by moving the particle beam energy attenuator in the single direction in which the thickness thereof changes. 7. The particle beam therapy system according to claim 6, wherein the predetermined angle is 90°. 8. The particle beam therapy system according to claim 1, wherein a collimator member having an opening of a predetermined size is provided at a position, between the variable energy attenuation unit and the irradiation unit, through which a particle beam passes.