Present state of the theory of the MHD equilibrium and stability of stellarator plasmas

The MHD theory of the equilibrium and stability of the plasma in a stellarator is set forth. Various ways to develop magnetic configurations of the stellarator type are examined. The basic characteristics of the devices presently in operation are reported. The method of averaging over the rapidly varying spatial variable is described. This method is used to study the plasma equilibrium and also the stability with respect to current-driven kink modes and ballooning modes. The limiting plasma pressure, determined jointly by the conditions for plasma equilibrium and stability, is discussed. Methods for raising this limit are described. The present state of the theory of the MHD equilibrium and stability of plasmas in stellarators is summarized. The basic problems for further development of this theory are outlined.