Patent Number: 
Section: claims

1. A neutron capture therapy system comprising:an accelerator, wherein the accelerator generates a charged particle beam;a neutron generator, wherein the neutron generator generates a neutron beam after being irradiated by the charged particle beam;a vacuum tube, wherein the vacuum tube transports the charged particles accelerated by the accelerator to the neutron generator;a beam shaping assembly, wherein the beam shaping assembly comprises a moderator and a reflector surrounding the moderator, the moderator moderates the neutrons generated by the neutron generator to a preset spectrum, and the reflector leads the deflected neutrons back to increase the neutron intensity within the preset spectrum; anda collimator, wherein the collimator concentrates the neutrons generated by the neutron generator,wherein the spectrum of the neutron beam is changed by changing the spectrum of the charged particle beam. 2. The neutron capture therapy system according to claim 1, wherein the neutron capture therapy system further comprises a microwave generator capable of injecting microwaves into the accelerator, the spectrum of the charged particle beam output by the accelerator changes according to the injected microwaves at different frequencies, when the spectrum of the charged particle beam is at a first value, the charged particle beam reacts with the neutron generator and generates a spectrum of neutron beam at a first value, and when the spectrum of the charged particle beam is at a second value, the charged particle beam reacts with the neutron generator and generates a spectrum of neutron beam at a second value, wherein the spectrum of the first value of the charged particle beam is lower than that of the second value, and the spectrum of the first value of the neutron beam is lower than that of the second value, and wherein the neutron capture therapy system indirectly changes the spectrum of the neutron beam by changing the beam energy spectrum of the charged particle beam, and then changes the neutron depth dose distribution. 3. The neutron capture therapy system according to claim 1, wherein the spectrum of the charged particle beam changes as the changing of electric field intensity of the accelerator, an electric field generating device is provided outside the vacuum tube and/or the neutron generator, the electric field generating device is capable of generating an electric field and so as to accelerate or decelerate the charged particle beam before the charged particle beam irradiates to the neutron generator. 4. The neutron capture therapy system according to claim 1, wherein the neutron capture therapy system further comprises a beam energy spectrum adjusting member capable of adjusting the spectrum of the charged particle beam, when the beam energy spectrum adjusting member is located in the vacuum tube and is in front of the neutron generator, the spectrum of the charged particle beam is adjusted after irradiating to the beam energy spectrum adjusting member, and then the charged particle beam irradiates to the neutron generator to generate the neutron beam. 5. The neutron capture therapy system according to claim 4, wherein the vacuum tube is provided with an accommodating portion, the beam energy spectrum adjusting member is accommodated in the accommodating portion and is connected with a driving mechanism capable of moving the beam energy spectrum adjusting member, when the driving mechanism controls the beam energy spectrum adjusting member to move to the front of the neutron generator, the spectrum of the charged particle beam changes after irradiating to the beam energy spectrum adjusting member and then irradiates to the neutron generator; when the driving mechanism controls the beam energy spectrum adjusting member to be accommodated in the accommodating portion but not in front of the neutron generator, the charged particle beam directly irradiates to the neutron generator. 6. The neutron capture therapy system according to claim 5, wherein the neutron capture therapy system comprises a plurality of beam energy spectrum adjusting members, and the driving mechanism drives each beam energy spectrum adjusting member to move separately to adjust the spectrum of the charged particle beam. 7. The neutron capture therapy system according to claim 5, wherein the beam energy spectrum adjusting members are made of different materials. 8. The neutron capture therapy system according to claim 1, wherein the neutron generator is connected to a power supply device and energized by the power supply device, and the beam spectrum of the charged particle beam changes after the charged particle beam irradiates to the energized neutron generator. 9. A neutron capture therapy system comprising:an accelerator, wherein the accelerator generates a charged particle beam;a neutron generator, wherein the neutron generator generates a neutron beam after being irradiated by the charged particle beam;a vacuum tube, wherein the vacuum tube transports the charged particles accelerated by the accelerator to the neutron generator;a beam shaping assembly, wherein the beam shaping assembly comprises a moderator and a reflector surrounding the moderator, the moderator moderates the neutrons generated by the neutron generator to a preset spectrum, and the reflector leads the deflected neutrons back to increase the neutron intensity within the preset spectrum;a collimator, wherein the collimator concentrates the neutrons generated by the neutron generator; andat least a beam energy spectrum adjusting member, wherein before the charged particle beam irradiates to the neutron generator, the charged particle beam irradiates to the beam energy spectrum adjusting member and achieves adjustment of the charged particle beam spectrum. 10. The neutron capture therapy system according to claim 9, wherein the beam energy spectrum adjusting member is located in the vacuum tube and is able to move from a first location to a second location, when the beam energy spectrum adjusting member is in the first location, the charged particle beam irradiates to the beam energy spectrum adjusting member before irradiating to the neutron generator; when the beam energy spectrum adjusting member is in the second location, the charged particle beam directly irradiates to the neutron generator. 11. The neutron capture therapy system according to claim 10, wherein a plurality of beam energy spectrum adjusting members are located in the vacuum tube and move from a first location to a second location separately. 12. The neutron capture therapy system according to claim 11, wherein the vacuum tube is provided with an accommodating portion located below the neutron generator, the beam energy spectrum adjusting members are accommodated in the accommodating portion, and each beam energy spectrum adjusting member is able to move upward to the first location or downward to the second location separately. 13. The neutron capture therapy system according to claim 11, wherein the beam energy spectrum adjusting members are in the same structure but with different thicknesses. 14. The neutron capture therapy system according to claim 11, wherein the beam energy spectrum adjusting members are made of different materials. 15. The neutron capture therapy system according to claim 14, wherein at least one of the beam energy spectrum adjusting members is made of materials capable of generating a neutron beam. 16. The neutron capture therapy system according to claim 9, wherein the cross sections of the beam energy spectrum adjusting member and the neutron generator perpendicular to the irradiation direction of the charged particle beam are circular. 17. A neutron capture therapy system comprising:an accelerator for generating a charged particle beam;a neutron generator for generating a neutron beam after being irradiated by the charged particle beam;a vacuum tube for transporting the charged particles accelerated by the accelerator to the neutron generator;a beam shaping assembly including a moderator for moderating the neutrons generated by the neutron generator to a preset spectrum and a reflector surrounding the moderator for leading the deflected neutrons back to increase the neutron intensity within the preset spectrum;a collimator for concentrating the neutrons generated by the neutron generator; andmeans for changing the spectrum of the charged particle beam whereby the spectrum of the neutron beam changes. 18. The neutron capture therapy system according to claim 17, wherein a plurality of beam energy spectrum adjusting members are located in the vacuum tube, and move from the first location to the second location separately.