Patent Number: 
Section: claims

1. A fission power generator, comprising:a sub-critical core, anda plurality of proton beam generators, each of the proton beam generators configured to concurrently provide a proton beam into a different area of the sub-critical core;wherein each proton beam scatters neutrons within the sub-critical core, and the plurality of proton beam generators provide aggregate power to the sub-critical core, via the proton beams, to scatter neutrons sufficient to initiate fission in the sub-critical core;wherein the proton beam generators are isochronous cyclotrons, each of the cyclotrons comprising folded radio frequency cavities each cavity comprising a horizontal lobe disposed above a proton beam aperture and a horizontal lobe disposed below the proton beam aperture, wherein each lobe extends lengthwise along an orbital plane of the cyclotron. 2. The fission power generator of claim 1, wherein the cyclotrons are configured to share a flux return in a sector magnet flux-coupled stack. 3. The fission power generator of claim 2, wherein a beam aperture of the sector magnet flux-coupled stack comprises pole faces having ridges aligned in curvature of beam travel, the ridges producing at least a quadrupole gradient that focuses a proton beam passing through the aperture. 4. The fission power generator of claim 3, wherein each ridge comprises faces and each face comprises superconducting windings that produce at least a quadrupole gradient that focuses the proton beam passing through the aperture. 5. The fission power generator of claim 2, wherein a beam aperture of the sector magnet flux-coupled stack comprises pole faces having windings that produce at least a quadrupole gradient that focuses a proton beam passing through the aperture. 6. The fission power generator of claim 2, wherein the longitudinal sides of the sector magnet flux coupled stack are flat. 7. The fission power generator of claim 1, wherein the sub-critical core comprises a molten mixture of fuel salt and heavy carrier salt. 8. The fission power generator of claim 7, further comprising:a core vessel; anda containment vessel;wherein the core vessel comprises:an inner vessel that contains the molten mixture;a lead outer vessel disposed about the inner vessel; anda multi-layer heat shield disposed between the inner vessel and the outer vessel. 9. The fission power generator of claim 8, wherein a space between the inner vessel and the outer vessel comprises helium while configured to conduct heat from the inner vessel to the outer vessel, and comprises vacuum while configured to inhibit heat conduction from the inner vessel to the outer vessel. 10. The fission power generator of claim 8, further comprising a lanthanide distillation system disposed within the containment vessel, wherein, during power generator operation, the lanthanide distillation system extracts lanthanides from the molten mixture, and stores the lanthanides in a lanthanide storage vessel. 11. The fission power generator of claim 8, further comprising heat pipes coupled to the outer vessel, the heat pipes configured to conduct heat away from the outer vessel. 12. The fission power generator of claim 8, further comprising a cryotrap disposed within the containment vessel, wherein the cryotrap configured to extract volatiles the sub-critical core. 13. The fission power generator of claim 1, further comprising a plurality of spallation targets disposed within the sub-critical core, wherein at least one spallation target receives protons from each of the proton beam generators, and ejects neutrons based on the received protons. 14. The fission power generator of claim 1, wherein each proton beam comprises at least 700 megaelectronvolts of energy and the plurality of proton beams comprises at least 10 megawatts of power.