Compact tori

The design of conventional toroidal fusion reactors is constrained by the need to link the plasma torus (and its surrounding blanket) with a set of toroidal-field-generating coils. Compact-torus research is aimed at the objective of creating stable toroidal plasma entities in the absence of an external toroidal field, so that the conventional constraint on reactor design can be removed. Two basic types of grossly stable compact tori have been demonstrated experimentally and theoretically: (1) A low-aspect-ratio toroid of oblate spheroidal outer contour, with finite internal toroidal field (commonly called 'spheromak') can be formed by a 'magnetized' coaxial plasma gun, or by a reverse-poloidal-field pinch, or by the transformer action of a 'magnetic flux core'. (2) A plasma toroid with a prolate (racetrack-shaped) confining poloidal field and strictly null toroidal field can be formed by dynamic reverse-poloidal-field pinch techniques. (orig.)