Dispersion of ion-acoustic waves

Abstract

The dispersion of ion-acoustic waves in quiescent rare-gas discharge plasmas has been investigated experimentally and theoretically. Experimentally, various grid systems were used to generate the waves which were studied using a time-of-flight technique. The experimental results show that two separate propagating phenomena appear. The slower propagating disturbance is the ion-acoustic wave, obeying the theoretically predicted dispersion behavior. The faster propagating disturbance, though superficially resembling a wave, is composed of bursts of ions produced by the driving potentials placed on the grids and would appear to be related to the "free streaming" term found by Landau. Previous theoretical models of ion-wave propagation have untilized either purely initial-value or steady-state, boundary-value calculations. A model is presented which more nearly simulates the experimental time-of-flight studies of finite packets of ion waves generated by finite sine-wave bursts.