Patent Number: 
Section: claims

1. An ion beam delivery method for delivering, through an beam delivery nozzle, an ion beam extracted from a synchrotron, the method comprising the steps of:rotating a wheel installed in said beam delivery nozzle and having a plurality of stepped portions arranged in the rotating direction and having different thicknesses in an axial direction of the wheel to change energy of said ion beam passing said wheel; andintroducing said ion beam to pass at least a part of said plurality of stepped portions of said wheel and controlling start and stop of extraction of said ion beam from said synchrotron in each of the stepped portions in said at least a part thereof which said ion beam passes, during rotation of said wheel. 2. The ion beam delivery method according to claim 1, wherein the control for the start of extraction of said ion beam from said synchrotron is performed in accordance with a rotational angle of said wheel. 3. The ion beam delivery method according to claim 1, wherein the start and stop of extraction of said ion beam from said synchrotron are performed by controlling start and stop of supply of an RF power to an RF-applying device associated with said synchrotron. 4. The ion beam delivery control method according to claim 1, wherein said start of extraction of said ion beam from said beam generator is controlled in accordance with a rotational angle of said wheel measured by a rotational angle sensor provided in said beam delivery nozzle. 5. The ion beam delivery method according to claim 1, wherein the extraction control is performed in accordance with the rotational angle of said wheel, and the extraction stop control is performed in accordance with a measured value of the dose of said ion beam passing said beam delivery nozzle. 6. The ion beam delivery method according to claim 1, wherein the extraction of said ion beam is stopped when an accumulated value of the measured dose of said ion beam passing said beam delivery nozzle has reached a target dose. 7. The ion beam delivery method according to claim 1, wherein control of performing the start and stop of extraction of said ion beam from said synchrotron includes control for start of the extraction of said ion beam in at least the part of said plurality of stepped portions and control for stop of the extraction of said ion beam, the latter control being performed in accordance with a measured dose value of said ion beam passing said beam delivery nozzle. 8. An ion beam delivery equipment for delivering a ion beam to an irradiation target, the equipment comprising:a synchrotron for accelerating said ion beam;an beam delivery nozzle including a wheel having a thickness varied in the rotating direction to change energy of said ion beam passing said wheel, and delivering said ion beam having passed said wheel to said irradiation target; anda controller for controlling start and stop of extraction of said ion beam from said synchrotron during rotation of said wheel,said wheel having a plurality of stepped portions arranged in the rotating direction and having different thicknesses in an axial direction of the wheel,said controller introduces said ion beam to pass at least a part of said plurality of stepped portions of said wheel and controls the start and stop of extraction of said ion beam from said synchrotron in each of the stepped portions in said at least a part thereof which said ion beam passes. 9. The ion beam delivery equipment according to claim 8, wherein said synchrotron includes an RF-applying device, and said controller controls the start and stop of extraction of said ion beam from said synchrotron and controls start and stop of supply of an RF power to said RF-applying device. 10. The ion beam delivery equipment according to claim 8, further comprising a dose monitor for detecting a dose of said ion beam passing said beam delivery nozzle,wherein said controller controls the extraction of said ion beam from said synchrotron in the part of said plurality of stepped portions in accordance with the rotational angle of said wheel, and stops the extraction of said ion beam from said synchrotron in one of the part of said plurality of stepped portions when a dose value detected by said dose monitor has reached a target dose for the one stepped portion. 11. The ion beam delivery equipment according to claim 8, further comprising a dose monitor for detecting a dose of said ion beam passing said beam delivery nozzle,wherein said controller stops the extraction of said ion beam from said synchrotron when an accumulated dose value detected by said dose monitor has reached a target dose. 12. The ion beam delivery equipment according to claim 8, wherein saidcontroller controls said start of extraction of said ion beam from said synchrotron in accordance with a rotational angle of said wheel. 13. The ion beam delivery equipment according to claim 12, wherein said synchrotron includes an RF-applying device, and said controller controls the start and stop of extraction of said ion beam from said synchrotron and controls start and stop of supply of an RF power to said RF-applying device. 14. The ion beam delivery equipment according to claim 12, wherein said beam delivery nozzle includes a rotational angle sensor for detecting the rotational angle of said wheel, and said controller controls the start of extraction of said ion beam in accordance with the rotational angle measured by said rotational angle sensor. 15. The ion beam delivery equipment according to claim 14, wherein said synchrotron includes an RF-applying device, and said controller controls the start and stop of extraction of said ion beam from said synchrotron and controls start and stop of supply of an RF power to said RF-applying device.