Particle-in-cell simulations of parametric decay instability of radiofrequency wave in the ion cyclotron range of frequency in an inhomogeneous plasma

Abstract

Abstract Particle-in-cell simulations have been conducted to investigate the parametric decay processes of radiofrequency waves in the ion cyclotron range of frequency in inhomogeneous plasmas. By choosing the parameters close to those in the ion Bernstein wave heating experiments on the HT-7 tokamak (Li et al 2001 Plasma Phys. Control. Fusion 43 1227–38 ), decay channels similar to experimental observations have been found in simulations. It is shown that due to strong inhomogeneity of tokamak edge plasma, layers may exist where selection rules of the mode–mode coupling are satisfied, and resonant parametric decays can occur if the input wave power is sufficiently high. As a result, daughter waves at half-, second- and third-harmonic frequencies of the pump wave can be excited. The nonresonant parametric decay is also observed, and ions are heated via nonlinear Landau damping.