Axisymmetric Magnetic Mirror Fusion-Fission Hybrid

Early application of the simple axisymmetric mirror, requiring intermediate performance between a neutron source for materials testing Q=P_fusion/P_input ~0.05 and pure fusion Q>10, are the hybrid applications. The Axisymmetric Mirror has attractive features as a driver for a fusion-fission hybrid system: geometrical simplicity, as well as the typical mirror features of inherently steady-state operation, and natural divertors in the form of end tanks. This level of physics performance has the virtue of being low risk with only modest R&D needed; and its simplicity promises economy advantages. Operation at Q~1 allows for relatively low electron temperatures, in the range of 3 keV, for the DT injection energy ~ 80 keV from existing positive ion neutral beams designed for steady state. A simple mirror with the plasma diameter of 1 m and mirror-to-mirror length of 40 m is discussed. Simple circular steady state superconducting coils are based on 15 T technology development of the ITER central solenoid. Three groups of physics issues are presented: axial heat loss, MHD stability, and microstability of sloshing ions.

Burning fission reactor wastes by fissioning transuranics in the hybrid will multiply fusion's neutron energy by a factor of ~10 or more and diminish the Q needed to overcome the cost of recirculating power for good economics to less than 2 and for minor actinides with multiplication over 50 to Q~0.2. Hybrids that obtain revenues from sale of both electricity and production of fissile fuel with fissioning blankets might need Q<2 while suppressing fissioning might be the most economical application of fusion but will require Q>4.