The question of maintaining plasma equilibrium in a three-turn stellarator by means of an external transverse field H⊥ is investigated in an ideal magnetohydrodynamic model as a first approximation with respect to β, where β is the ratio of the gas-kinetic pressure of the plasma to the magnetic pressure. An “island” structure of the paraxial magnetic surfaces is observed under conditions of precise compensation and slight undercompensation of the homogeneous component of the plasma magnetic field by the field H⊥. The optimum conditions are found for controlling the position of the magnetic axis with an external transverse field. Relations are obtained for estimating the maximum equilibrium pressure of the plasma in a three turn stellarator in the presence of an external transverse magnetic field.

as compared with that in single-antenna operation, for the same net power. On the other hand, the radiation in in-phase operation is enhanced as compared with that in single-antenna operation. As a result of the reduction of the radiation loss by ICRF heating with phase control, the maximum attainable density without disruption is increased compared to that in the Ohmic heating phase. The remarkable differences in metal impurity emission and radiation loss are closely related to the amount of radiated power with parallel wavenumber near k tt = 0. The metal impurities are released by a mechanism closely related to the radiated power near k,, = 0; on the other hand, the light impurities are released by a different mechanism.

On the basis of differential and integral methods of solving the boundary value problem and with the help of poloidal-magnetic-field or flux measurements by means of probes located outside the vacuum chamber, methods which are insensitive to measurement errors are developed for determining the position and shape of the boundary magnetic surface in a tokamak.

Plasma transport across the magnetic field is studied in the presence of resonant helical magnetic perturbations giving rise to isolated magnetic islands.

The authors describe hybrid magnetic trap of the stellarator type (Unitron) employing a helical winding with four poles arranged in a certain way with respect to the minor azimuth. Combination of the helical conductors and current provides qualitatively different magnetic traps with spatial and plane magnetic axes. Analytical expression are derived for the various characteristics of the main types of Unitron trap. A study of the parameters of the Unitron shows that the system with the second and third harmonics of the helical field has better confinement properties.