Theory of rf current generation in a plasma

A theory is derived for the generation of a current in a plasma by an rf oscillator which excites waves in the plasma, which in turn interact with electrons through a Cerenkov resonance. General expressions are derived for the resulting current, the rf power pumped into the plasma, and the momentum. These expressions are used to study the maintenance of a current by waves with narrow and broad spectra. A distortion of the longitudinal-velocity distribution of the electrons which occurs away from the resonance region strongly affects the current. The interval of phase velocities which is best from the energy standpoint is determined for the case in which the excited waves have a narrow spectrum