Patent Number: 
Section: claims

1. A device for producing a 11C beam from a primary 12C beam, said device comprises a decelerator comprising hydrogen, H2, and configured to output said 11C beam suitable for external radiation therapy from said primary 12C beam incident on said decelerator, wherein said decelerator is a multi-medium decelerator comprising a hydrogen section followed by a decelerating section comprising a hydrogen rich material. 2. The device according to claim 1, wherein said decelerator comprises liquid H2. 3. The device according to claim 1, wherein said decelerator comprises a hydrogen section comprising said hydrogen H2 and having a thickness in an interval of from 20cm up to 70 cm. 4. The device according to claim 3, wherein said decelerator comprises said hydrogen section comprising said hydrogen H2 and having said thickness in an interval of from 20 cm up to 35 cm. 5. The device according to claim 1, wherein said decelerating section comprises a hydrogen rich plastic material. 6. The device according to claim 5, wherein said decelerating section comprises a hydrogen rich plastic material selected from the group of polyethylene and polypropylene. 7. The device according to claim 1, wherein said decelerating section comprises a hydrogen rich material selected from the group of liquid methane, liquid propane and liquid ammonia. 8. The device according to claim 1, wherein said decelerating section has a thickness selected to modulate a range of said 11C beam to reach a target depth in a subject to be irradiated by said 11C beam. 9. The device according to claim 1, wherein said decelerating section is in the form of a binary system of multiple slices of said hydrogen rich material. 10. The device according to claim 9, further comprising a slice adjuster configured to adjust a number of slices of said hydrogen rich material that are present in a beam path through said binary system to achieve a modulation of a range of said 11C beam. 11. The device according to claim 10, wherein said slice adjuster is configured to adjust said number N of slices of said hydrogen rich material to reduce said range of said 11C beam with an amount of      ∑          i      =      0              N      -      1        ⁢          ⁢            2      i        ⁢                  ⁢          mm      .       12. The device according to claim 1, wherein said decelerator is configured to output said 11C beam suitable for simultaneous external radiation therapy and dose delivery verification using positron emission tomography or positron emission tomography-computed tomography imaging. 13. A radiation system comprising:a device according to claim 1 to produce a 11C beam from a primary 12C beam;a set of quadropoles downstream of said device and configured to focus said 11C beam;a beam size collimator downstream of said set of quadropoles and configured to impose an angular limitation to said 11C beam; anda particle species and energy selection system downstream of said beam size collimator and configured to output a therapeutic 11C beam having a beam quality useful for external radiation therapy. 14. The radiation system according to claim 13, wherein said particle species and energy selection system comprises a set of bending magnets and a beam particle species and energy collimator. 15. The radiation system according to claim 14, wherein said particle species and energy selection system further comprises a variable wedge filter configured to reduce an energy spread of said 11C beam. 16. The radiation system according to claim 15, wherein said variable wedge filter is in the form of a variable liquid medium wedge filter with solid walls. 17. The radiation system according to claim 16, wherein said variable wedge filter is in the form of a variable liquid hydrogen, H2, wedge filter. 18. The radiation system according to claim 15, wherein said variable wedge filter comprises two axially rotatable wedges. 19. The radiation system according to claim 15, wherein said variable wedge filter is a multi-layer wedge. 20. The radiation system according to claim 13, further comprising a 12C beam provider configured to provide said primary 12C beam. 21. The radiation system according to claim 20, wherein said 12C beam provider comprises an ion source configured to produce 12C ions and a cyclotron configured to accelerate said 12C ions to form said primary 12C beam. 22. A method of producing a 11C beam from a primary 12C beam, said method comprising directing said primary 12C beam onto a device as defined in claim 1, said 11C beam suitable for external radiation therapy exiting said decelerator. 23. A radiation system comprising:a device for producing a 11C beam from a primary 12C beam, said device comprises a decelerator comprising hydrogen, H2, and configured to output said 11C beam suitable for external radiation therapy from said primary 12C beam incident on said decelerator;a set of quadropoles downstream of said device and configured to focus said 11C beam;a beam size collimator downstream of said set of quadropoles and configured to impose an angular limitation to said 11C beam; anda particle species and energy selection system downstream of said beam size collimator and configured to output a therapeutic 11C beam having a beam quality useful for external radiation therapy, wherein said particle species and energy selection system comprises:a set of bending magnets,a beam particle species,an energy collimator, anda variable wedge filter in the form of a variable liquid hydrogen, H2, wedge filter with solid walls and configured to reduce an energy spread of said 11C beam.