Gas-Discharge High-Frequency Generators for Materials Processing

A new approach to the selection of high-frequency oscillations generated in high-voltage glow discharge plasma is developed. It is based on the appearance of pressure pulsations arising during collisions of the inflowing working gas stream with an obstacle. A spatial inhomogeneity in concentration of high-voltage glow discharge plasma (14 kV and 30 mA) caused by pressure pulsations results in discharge combustion instability. The difference between the ignition and combustion voltages of the discharge provides the ionization processes as well as the high-frequency (HF) oscillations at a frequency of 5 MHz selected by an oscillatory circuit. The fraction of power transformed into HF-oscillations reaches 40%. Testing of this oscillator in etching of a lithium niobate crystal demonstrates that the surface charges are removed from the substrate not only by the plasma, but also by displacement and recharge currents. An etching rate of 5 mu m/h has been achieved.