Experimental studies of plasma confinement in toroidal systems

Toroidal confinement schemes for controlled thermonuclear fusion are reviewed, with attention given to recent developments in tokamak, low-beta stellarator and high-beta research. Plasma energy loss processes caused by lack of plasma equilibrium, MHD or fluid instability, microinstabilities, collisional diffusion and thermal conduction across magnetic-field lines, and radiation losses are treated. Fluid instabilities, which become significant as energy density and plasma pressure are raised, receive particular consideration; methods of eliminating microinstabilities (associated with Bohm diffusion) are also mentioned. Ion number densities, temperatures and containment times are discussed for high-beta stellarators, toroidal pinches, and the internal-ring devices known as levitrons and multipoles.