What is a spheromak?
Spheromaks are unique for several reasons. First, a spheromak is simply connected, meaning no coils link the plasma through the central axis. A simply connected geometry provides a number of design and economical advantages towards the development of a fusion reactor. Another unique feature of the spheromak is that toroidal flux (represented by the blue arrow in the figure) exists at the center, but not at the walls of the spheromak. The toroidal flux at the center of the spheromak, generated from the relaxation of the magnetic field lines, is important for equilibrium. Overall, the toroidal and poloidal field magnitudes are comparable for a spheromak. Spheromak magnetic fields are primarily generated by internal plasma currents; therefore equilibrium is achieved without the use of external coils linking the plasma. Below is a figure of a typical spheromak equilibrium.
Figure 1 from http://www.llnl.gov/str/September05/Hill.html