Patent Number: 
Section: claims

1. A radiation therapy system for irradiating an irradiation object with particle beams of a predetermined energy, said radiation therapy system comprising:a particle accelerator configured to provide a particle beam for a single treatment station;a beam line assembly coupled to said particle accelerator and operable to direct said particle beam along a first direction;an energy degrader operable to attenuate an energy of said particle beam; anda gantry assembly coupled to said beam line assembly and comprising dipole magnets configured to generate variable magnetic fields,wherein said variable magnetic fields are operable to select a portion of said particle beam with said predetermined energy for irradiating said irradiation object and redirect said portion of said particle beam to a predetermined direction. 2. The radiation therapy system of claim 1, wherein said variable magnetic fields are externally controlled by electrical current in coils surrounding said dipole magnets. 3. The radiation therapy system of claim 1, wherein said variable magnetic fields are controlled by a software program based on a prescribed treatment plan. 4. The radiation therapy system of claim 1, wherein said energy degrader is disposed in said gantry assembly, and wherein said gantry assembly comprises a swiveling gantry configured to rotate up to an angel that is greater than 180° and less than 270° . 5. The radiation therapy system of claim 4, wherein said energy degrader comprises an exit opening configured to narrow a spatial crosssection of said particle beam exiting said exit opening. 6. The radiation therapy system of claim 4, wherein said energy degrader comprises an exit opening configured to narrow an energy spectrum of said particle beam exiting said exit opening. 7. The radiation therapy system of claim 4, wherein said gantry assembly comprises no collimator. 8. The radiation therapy system of claim 1, wherein said predetermined direction deviates from said first direction by 135°. 9. The radiation therapy system of claim 1, wherein said particle accelerator comprises a superconducting synchrocyclotron. 10. The radiation therapy system of claim 1, wherein said particle beam comprises particles selected from a group consisting of protons, neutrons, He ions and C ions. 11. The radiation therapy system of claim 1, wherein said predetermined direction directs to an isocenter. 12. A proton radiation therapy system configured to provide proton beam radiation to a single treatment station, said proton radiation therapy system comprises:a cyclotron coupled to a proton source;a beam line assembly coupled to said cyclotron and operable to direct a proton beam to a gantry assembly;an energy degrader operable to attenuate an energy of said proton beam;said gantry assembly coupled to said beam line assembly and comprising: a plurality of dipole magnet configured to generate variable magnetic fields,wherein said variable magnetic fields are operable to select a portion of said proton beam with a predetermined energy for irradiating said irradiation object and to redirect said portion of said proton beam to a predetermined direction. 13. The proton radiation therapy system of claim 12, wherein said variable magnetic fields are externally controlled by electrical current in coils surrounding said plurality of dipole magnets, and wherein said electrical current is controlled by a software program based on a prescribed treatment plan. 14. The proton radiation therapy system of claim 12, wherein said energy degrader is disposed in said gantry assembly, and wherein said gantry assembly comprises a swiveling gantry configured to rotate in a range of 0˜270°. 15. The proton radiation therapy system of claim 12, wherein said energy degrader comprises an exit opening configured to narrow a spatial crosssection of said proton beam exiting said exit opening. 16. The proton radiation therapy system of claim 12, wherein said energy degrader comprises an exit opening configured to narrow an energy spectrum of said proton beam exiting said exit opening. 17. The proton radiation therapy system of claim 12, wherein said gantry assembly comprises no collimator, and wherein said cyclotron is a super conducting cyclotron. 18. The proton radiation therapy system of claim 12, wherein variable magnetic fields are configured to bend said proton beam by 90°. 19. The proton radiation therapy system of claim 12, wherein said energy degrader is exposed to atmosphere. 20. The proton radiation therapy system of claim 12, wherein said predetermined direction directs to an isocenter.