Discharge improvement with hf field of plasma generated by an electron beam

Summary form only given, as follows. We studied experimentally the plasma discharge process of Ar gases by an electron beam injection parallel to the magnetic field. The plasma discharge via gas breakdown was explained by the production of higher energy electrons based on the cyclotron damping of unstable electron cyclotron harmonic waves in an electron beam-plasma system. On the condition of higher gas pressure and lower external magnetic field, we have observed that the generated plasma diffuses perpendicularly to the magnetic field and disrupts rapidly in short time regardless of the existence of beam injection. The disruption of the plasma discharge is attributed to the occurrence of unstable waves with low frequency by beam-plasma interaction. We have investigated the dispersion relation of these unstable waves and compare with the numerical dispersion of lower hybrid waves. The observed wave number and frequency agree well with numerical ones, therefore unstable waves with the low frequency are identified as lower hybrid waves. With these unstable waves, the discharge plasma is diffused in the radial direction perpendicular to the magnetic field and disrupts.