ABSTRACT
A stellarator field can provide a steady-state magneto-hydrodynamic equilibrium configuration of plasma only by the external field produced by the coils outside the plasma. The rotational transform, which is necessary to confine the toroidal plasma, is formed by the external coils so that the stellarator has the merit of steady-state confinement. Although Stellarator C [6.1] was rebuilt as the ST tokamak in 1969 at the Princeton Plasma Physics Laboratory, confinement experiments by Wendelstein 7A, 7AS, Heliotoron-E, and ATF are being carried out, because there is a merit of steady-state confinement without current-driven instabilities. Large helical device LHD started experiments in 1998 and advanced stellarator WVII-X is under construction.
