Simulation And Experimental Study On Microwave Attenuation In Plasma

The interaction between plasma and electromagnetic wave is widely used in many fields, such as plasma stealth, plasma antenna, and so on. In this paper, the effects of various uniform and non-uniform plasma objects on microwave propagation are studied. In addition, the attenuation of microwave in discharge plasma is investigated experimentally.First, the influences of uniform and non-uniform planar plasma, plasma column, and plasma column array on microwave propagation are investigated at different parameters by using finite difference time domain(FDTD) method. The results show that the absorptance of microwave through the planar plasma decreases firstly with the increase of the collision rate and then decreases. When the thickness of planar plasma is greater than the penetration depth of microwave, high density plasma can block the microwave. The maximum absorptive frequency of microwave increases with the increase of planar plasma frequency increasing. For the plasma column, the microwave can be scattered by the non-uniform plasma column to two symmetrical directions. The higher the plasma frequency is, the more the scattered microwave power. The offset angle of scattered microwave is also increasing with the plasma frequency in underdense plasma column. In addition, increasing the collision rate in underdense plasma column will decrease the scattered microwave power. The uniform plasma column array has similar properties with the planar plasma in the absorptive characteristic for the microwave.Then, the attenuation of microwave in cylindrical non-uniform discharge plasma and plasma column array is investigated through experiments. The cylindrical non-uniform plasma was generated by hollow cathode discharge(HCD). The experimental results show that the microwave reflectance decreases with the increase of discharge current in whole frequency range of 2~12GHz. In the case of plasma column array, the microwave reflectance also decreased with the increase of discharge current. And the plasma column arrays have selective absorption of microwave, the larger the discharge current(or plasma density) is, the higher the maximum absorptive frequency for microwave.