A Pulse-Operated Microwave-Induced Plasma Source

A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational difficulties of the MIP due to Joule heating and to obtain spectral emission lines of high peak intensities, one energizes the MIP source with a TM₀₁₀ cavity with a microwave pulse of large peak power and short duration, which is superposed on a low-bias dc microwave. A peak power of 400 W, which is two times the maximum output ratings of a magnetron under a normal dc operation, can be generated by applying a −500 V pulse to the cathode of the magnetron operating under the bias mode. The pulsed-MIP requires no special cooling system since the mean power remains low during the entire operation. Some of the considerations taken into account in the design and construction of the microwave generator are presented. The electrical and spectral characteristics of the MIP source are also described in detail.