Parametric Instabilities in Lower-Hybrid-Frequency Heating of a Tokamak

Abstract

Decay spectra during the rf heating were identified as the parametric decay into the cold lower-hybrid waves and the ion-cyclotron waves at the plasma surface. The decay instabilities absorbed some fraction of the rf power, hence they affected the plasma heating. However, they did not prevent the penetration of the lower hybrid wave to the plasma center. Drastic reduction of the decay spectra was obtained when the resonant parametric decay condition was destroyed.