Ion Cyclotron Parametric Instability and Associated Ion Heating in a Two-Ion Species Plasma

Abstract

Theoretical and experimental studies are presented on a parametric decay instability into two electrostatic ion cyclotron waves in a two-ion species plasma. Theoretically, by using a hot-electron plasma model, we generalize such a decay instability in the limits of long- and short-wavelength regions. The instability thresholds as well as the growth rates are predicted for these limiting cases. Experimentally, we modulate an electron beam near the sum of the ion cyclotron frequencies in an electron-beam-plasma system to produce an electric field in the radial direction. At high levels of beam modulation above a certain threshold, the beam pumps this instability. Associated ion heating takes place as the instability develops strongly. The instability threshold has been determined in a parameter space. The instability threshold predicted theoretically is compared with that obtained experimentally, and a quantitative agreement is obtained between them.