Modeling of the Excitation of Electron Bernstein Modes in Spherical Tokamaks

The possibility is studied of using electron cyclotron waves to heat plasmas and to drive currents in spherical tokamaks when the cutoff layer for the waves is located at the plasma edge. It is shown that, by optimizing the method for the excitation of electron cyclotron waves, it is possible to achieve conditions corresponding to the so-called “radio window” effect, i.e., conditions under which the efficient conversion of incident waves into Bernstein modes propagating toward the plasma center occurs already at the plasma edge. As an example, the parameters of multiwaveguide antennas capable of emitting directed penetrating radiation are calculated.