High frequency oscillations in a bounded thermally produced plasma

Abstract

Measurements are reported of a high frequency mode of oscillation of a current carrying, bounded, thermally produced plasma. The oscillation occurs at approximately a third of the electron plasma frequency. A linear theory is presented, which predicts an instability at this frequency. The electron and ion velocity distribution functions used in this theory are determined by the self-consistent d.c. potential distribution. An interesting feature is that the electron velocity distribution function is a discontinuous Maxwellian. The calculated frequency of the instability and its variation as a function of the plasma density agree very well with the experimental observations.