Steady state toroidal pinches

Several conceptual schemes have been suggested for running toroidal pinches in a steady state. A pinch is taken to mean any containment system in which a poloidal field (B-theta) produced by a plasma current is an essential feature of the containing magnetic field. Both tokamaks and diffuse pinches come into this category. In all existing experiments the current is pulsed, produced by the transformer action of a changing magnetic flux through the central region of the torus. Schemes for maintaining the toroidal current (I-phi) in steady state are reviewed. The main results are re-derived and critically assessed. (U.K.)