Ion Heating near the Lower Hybrid Frequency

Abstract

In a hot cathode d.c. discharge tube with mercury vapor, the rf electric field with a frequency up to 2 MHz was applied between an anode and a cathode in a static axial magnetic field. The electron temperature measured by a Langmuir probe and the ion temperature by an energy analyzer are studied as functions of the applied rf and static field parameters. The measured ion temperature markedly increased at several frequencies of the applied field. At the same time, the parametric excitation of oscillations in the plasma was observed by using a panoramic spectrum analyzer. There were excited oscillations with the same frequencies as that of the rf field which increased ion temperature. These effects are investigated by varying the ion density and the magnetic field strength. The results are consistent with an interpretation that one of the excited oscillations is the lower hybrid oscillation and it decays to heat the plasma.