Kinetic study on microwave discharge plasma and its afterglow

Gas discharge plasmas generated by μs-pulse focused microwaves are investigated. The model is based on a self-consistent solution to Helmholtz equation for microwave field, particle continuity equations, and the energy balance equations, coupled with plasma kinetics. Two recent experiments are studied: a. sub-megawatt (MW) X-band 9.4 GHz microwave breakdown in nitrogen; b. MW-class W-band 110 GHz microwave breakdown in 100-10 000 Pa air. In experiment a, the tracked density of electronic states N₂(C³Π_u) agreed with the measured intensity from second positive system (SPS) of optical emission spectroscopy (OES). In experiment b, the simulation results reproduced the dependence of nitrogen vibrational and translational temperature on air pressure measured by OES. The underlying mechanisms for the above coincidences are unveiled. (authors)