Stabilization of the Current-Driven Electrostatic Ion-Cyclotron Instability by Lower-Hybrid Waves

The current-driven electrostatic ion-cyclotron instability in a $Q$ machine operated in the low-density regime ${\left(\frac{{\omega }_{\mathrm{pe}}}{{\omega }_{\mathrm{ce}}}\right)}^2\ll 1$ is stabilized by externally generated rf electrostatic fields in the lower-hybrid range. Stabilization is due to a resonant ponderomotive force, which reduces the instability frequency, thus increasing the ion-cyclotron damping. The experimental results are in good agreement with an analysis which describes the effect of rf power on the instability frequency shift and growth rate.