Compact toroid experiments: Spheromaks and field-reversed configurations

Compact toroids (CT) containing both poloidal and toroidal magnetic field, spheromaks, are generated in the CTX experiment using a magnetized coaxial plasma gun, and are trapped and stably confined in an oblate flux conserver. Total configuration lifetimes are observed up to approx.=0.8 ms, consistent with classical resistive decay. The field reversed configuration (FRC) is a high beta, axisymmetric, highly prolate compact toroid, containing only poloidal magnetic field, formed in a field-reversed theta pinch. A quiescent confinement period of 30 to 90 μs with Tsub(i)approx.=200-500 eV and n-5x1015 cm-3 is terminated by an n=2 rotational instability. The FRC is stable to MHD modes including the tilting instability. (orig.)