Design and construction of a microwave plasma jet system for material processing

We have designed a 2.45GHz waveguide-based applicator to generate a Microwave Plasma Jet (MPJ) at atmospheric pressure. The MPJ system consists of a 1-6kW magnetron power supply, a circulator, a watercooled matched load and the applicator. The applicator includes a tuning section, which is required to reduce the reflected power, and the nozzle section. The plasma is formed by the interaction of the high electrical field, generated by the microwave power, between the waveguide aperture and the gas nozzle. A variety of gasses have been used to produce the plasma including argon, helium and nitrogen. A 2kW, 2.45GHz MPJ, constructed using a rectangular waveguide WG9A (WR340), has been investigated. An MPJ has been used for material processing applications including cutting welding, glass vitrification and quartz/ceramic processing. This paper discusses the design parameters and the potential of the MPJ for industrial applications and how the jet can be tailored to suit different tasks, by adjusting the various parameters such as the type of gas, the flow rate, the input power and the nozzle design.