A compact fusion reactor based on the staged compression of a field reversed configuration

A new methodology for achieving the formation and compressional heating of a field reversed configuration (FRC) plasmoid has been investigated both theoretically and experimentally at the University of Washington and MSNW. This approach, based on previous FRC empirical scaling, is expected to achieve fusion gain as large as 10. For the FRC, the fusion gain, G ∼ ϕp⋅Be2 where ϕp is the FRC poloidal flux and Be the confining axial magnetic field. G is essentially independent of the FRC radial scale making feasible a small, compact reactor. The necessary ϕp (>60 mWb) is achieved by employing a large formation chamber (∼0.8 m radius) combined with the requisite axial magnetic field reversal time (Eθ ∼ 20 kV m−1) for generating a high initial temperature (Ti > 1 keV) FRC. By employing the dynamic formation procedure, the FRC is accelerated to ∼100–150 km s−1. This subsonic velocity is maintained as the FRC is translated through a series of cylindrical coils of decreasing radius but of sufficient length (>LFRC) and number (∼10) to produce essentially an isentropic and adiabatic radial wall-compression of the equilibrium FRC. The final stage is a 12 cm diameter, 3–6 m long confinement and burn chamber with a vacuum field of 7–9 T produced by external solenoidal coils inside the flux conserving cylinder. The vacuum field is compressed by the FRC on insertion to 35 T resulting in fusion gain conditions for the 2–5 ms transit. The large ratio of FRC to inner wall radius (0.85) substantially lowers the FRC edge pressure thereby greatly reducing both particle and thermal losses. The resulting D–T fusion yield for the 3.5 MJ FRC is 20–40 MJ/pulse. The final ejection and expansion of the FRC into a large, low field mirror chamber provides a mechanism for FRC energy recovery. The experimental justification and the physics basis for the entire process from formation through burn of the Compact FRC Fusion Reactor concept is presented.