Patent Number: 
Section: claims

1. A charged particle therapy system including a charged particle beam generator for generating a charged particle beam and a charged particle beam irradiation apparatus comprising a range modulation wheel device through which the charged particle beam emitted from said charged particle beam generator passes,wherein said range modulation wheel device comprises a housing and a range modulation wheel disposed in said housing and rotatably mounted thereto so as to allow the charged particle beam to pass through the range modulation wheel. 2. A charged particle therapy system according to claim 1, wherein said charged particle beam irradiation apparatus further comprises a holding member for holding said range modulation wheel device in such a manner that the range modulation wheel device can be inserted into and removed from said holding member. 3. A charged particle therapy system according to claim 1 or 2, wherein said charged particle beam irradiation apparatus further comprises a range modulation wheel driver having a second rotary shaft in contact with a first rotary shaft of said range modulation wheel. 4. A charged particle therapy system according to claim 2, wherein said charged particle beam irradiation apparatus further comprises a pushing device for pushing said range modulation wheel device against said holding member in a releasable way. 5. A charged particle therapy system according to claim 1, wherein an identifier is attached to said housing and given with identification information for identifying said range modulation wheel device, and said charged particle therapy system further includes an erroneous installation determining unit for receiving the identification information and determining erroneous installation of said range modulation wheel device. 6. A charged particle therapy system according to claim 2, wherein an identifier is attached to said housing and given with identification information for identifying said range modulation wheel device, and said charged particle therapy system further includes an erroneous installation determining unit for receiving the identification information and determining erroneous installation of said range modulation wheel device. 7. A charged particle therapy system according to claim 3, wherein an identifier is attached to said housing and given with identification information for identifying said range modulation wheel device, and said charged particle therapy system further includes an erroneous installation determining unit for receiving the identification information and determining erroneous installation of said range modulation wheel device. 8. A charged particle therapy system according to claim 4, wherein an identifier is attached to said housing and given with identification information for identifying said range modulation wheel device, and said charged particle therapy system further includes an erroneous installation determining unit for receiving the identification information and determining erroneous installation of said range modulation wheel device. 9. A charged particle therapy system according to claim 1, wherein said range modulation wheel has a blade having a thickness different stepwise in the direction of passing of the charged particle beam. 10. A charged particle beam generator according to claim 9, wherein said range modulation wheel has a plurality of blades and an opening between two blades adjacent in the circumferential direction. 11. A range modulation wheel device comprising a housing and a range modulation wheel disposed in said housing and rotatably mounted thereto so as to allow a charged particle beam to pass through said range modulation wheel,said range modulation wheel having at least one blade having a thickness different stepwise in the direction of passing of the charged particle beam. 12. A range modulation wheel device according to claim 11, wherein said housing includes an identifier attached thereto. 13. A method of installing a range modulation wheel device, the method comprising the steps of:preparing a range modulation wheel device comprising a housing and a range modulation wheel disposed in said housing and rotatably mounted thereto;inserting said range modulation wheel device into a holding member provided in a charged particle beam irradiation apparatus; andpushing said housing against said holding member by a pushing member. 14. A method of installing a range modulation wheel device according to claim 13, further comprising the step of determining erroneous installation of said range modulation wheel device based on identification information attached to said housing by using an erroneous installation determining unit.