Spheromak Reactor: Physics Opportunities and Issues

The spheromak is a magnetic confinement device with a more attractive fusion reactor potential than the leading geometry, the tokamak. This results in large part from the absence of a toroidal field coil and other structures linking the plasma along the geometric axis. However, because of the lack of a strong external magnetic field, the physics is more complex so that considerable research is required to learn how to achieve the reactor potential. Several critical physics issues are considered here, including stability to low mode number magnetohydrodynamic (MHD) modes, energy confinement, helicity injection and current drive, the magnetic turbulence associated with this dynamo, and the beta (ratio of plasma and magnetic pressures) which can be supported in the geometry.