The Orical Studies Of Air Breakdown By Repetition-rate High Power Microwave Pulse

High Power Microwave (HPM) is mainly used in artificial ionosphere, repair of atmospheric ozone layer and self-organization plasma produced in air breakdown. In addition, HPM has important application in electronic war.With the improvement of power, the air breakdown has become the major problem in the study of HPM transmission. Pulse attenuation and the tail corrosion caused by air breakdown limit the energy of pulse transferred to the target, which reduce the utilization efficiency of pulse source, and the wave reflection caused by air breakdown damages the launch system. The repetition-rate HPM pulse causes the air breakdown more easily, when compared with the single pulse. Therefore, the study of the transmission of repetition-rate HPM pulse is very significant.First the paper presents basic concepts of microwave transmission and breakdown. By analyzing the research status of microwave breakdown at home and abroad, it is shown that the research of repetition-rate HPM pulse transmission is very necessary. Second we introduce several expressions of equivalent ionization parameters into the electron density and energy equations to predict the air breakdown threshold of single pulse under different pressures, and the comparison between simulated and experimental thresholds are carried out. The results show that the breakdown threshold reported by Ali agrees very well with the experimental data. On this basis, the variation of the maximum transmitted energy with the microwave amplitude is analyzed. Besides, the temporary evolution of HPM transmission in air breakdown is numerically simulated by using electron fluid model.In the research of air breakdown by repetition-rate HPM pulse, the global model is proposed to describe the electron relaxation process, which includes electron density equation and electron energy conservation equation. In the global model, the ionization rate, collision rate and the energy loss rate are obtained by solving the Boltzmann equation, and the empirical formulas for recombination rate and diffusion rate are adopted. The electron relaxation process after the breakdown is studied when the background gas is argon and nitrogen, respectively. It is shown that the argon breakdown time predicted by global model agree well with the result of Monte Carlo Collision (PIC/MCC) under different pressure. After the argon breakdown happens, electron density still grows in a short time and then declines, and the electron energy is decreased to the temperature of the background gas quickly. With the increase of the pressure, the electron density loss rate decreases, and the electron energy loss rate becomes faster, and the maximum value of electron density becomes lower. The electron relaxation time is longer in nitrogen breakdown, when compared with the case of argon.Finally the study of the air breakdown by the repetition-rate HPM pulse is summarized, and the development directions of these researches are pointed out.