Ion beam excitation of ion-cyclotron waves and ion heating in plasmas with drifting ions

Ion-cyclotron waves are excited by cesium and potassium ion beams in cesium and potassium Q-machine plasmas. The ion beams are injected along the magnetic field with care to avoid beam transverse velocities. The observed ion-cyclotron mode frequencies are below those driven by electron currents. These resonant instabilities are convective in character with small spatial growth rates k_i/k_r 0.05. Plasma ion heating is observed and is consistent with a model in which mode amplitudes are saturated by diffusion effects.