Study of the Current-Driven Ion-Acoustic Instability Using CO2-Laser Scattering

Abstract

The saturated state of the current-driven ion-acoustic instability in a He positive-column plasma is studied using C${\mathrm{O}}_2$-laser scattering and heterodyne detection. It is found that small concentrations of hydrogen present in the positive-column plasma play a crucial role in saturating the instability. The measured angular extent and level of saturation of the turbulence are found to be consistent with "resonance-broadening"-enhanced ion Landau damping by 1 to 4% ${\mathrm{H}}^{+}$ impurity ions.