Efficient production of microwave bubble plasma in water for plasma processing in liquid

Microwave bubble plasma in water is a novel plasma applicable to the processing of materials in liquid. An electromagnetic simulation of slot excitation of microwaves reveals that the electric field at a slot antenna is significantly influenced by the size of the bubble existing in front of the antenna. To improve the power efficiency and the plasma stability, a bubble control plate is installed adjacent to the antenna, the effect of which on the electric field enhancement is confirmed in the simulation. Furthermore, three slot antennas are newly developed. According to these modifications of the microwave excitation system, a dramatic increase in the decomposition efficiency of an organic solute by a factor of 20 is found in the experiment.