Microwave Transmission In Helium Plasma Of DC Grid Anode Discharge

Plasma as the fourth state of matter exists,and its special composition makes it have many applications,so it attracts more and more researchers to study.The charged particles in the plasma are in a free state and are easily affected by external electric and magnetic fields.This characteristic of charged particles in plasma has aroused the enthusiasm of researchers for studying the influence of plasma on the transmission of electromagnetic waves,and applied it to many fields such as aerospace,aviation,defense and basic research.Designing experiments,generating large-area plasma in the laboratory,and conducting experimental research on electromagnetic wave transmission in the plasma can further explore the influence of plasma on the transmission of electromagnetic waves,and has important application value and academic significance.In this paper,firstly,a new grid discharge device is designed,and its discharge characteristics are experimentally studied.The plasma generating device adopts a thin column cathode array,uses helium gas as the ionizing gas,and forms a plasma layer with a certain thickness outside the anode in cooperation with the grid anode.The effects of breakdown voltage,gas pressure,and electrode spacing on the discharge characteristics were measured,and Pasing curves and volt-ampere characteristic curves under different conditions were obtained.Through comparative experiments,it was found that the Pasing curve between the new grid electrode structure and the ordinary metal plate electrode structure was inconsistent,and the optimal discharge scheme of the device was obtained.On this basis,a microwave transmission experiment system was built,and the microwave transmission characteristics of the plasma generated by DC grid anode helium discharge were experimentally studied.Using a high-frequency horn antenna connected to a vector network analyzer to measure the phase parameters of the echo,compared with the phase without plasma,the electron density of the plasma was obtained.Further,the microwave reflection characteristics of the plasma were measured,and the amplitude change of the microwave after being reflected by the electrode and then reflected by the electrode and again passing through the plasma was obtained;each discharge parameter of the plasma device was adjusted to obtain microwave reflection under different conditions characteristic.At the same time,the plasma parameters were obtained by measurement,with the help of the Z-transform time-domain finite difference method(Finite-difference timedomain-FDTD),the microwave transmission characteristics of the device were numerically simulated and measured under different conditions in the experiment The results were compared and analyzed to obtain more consistent results.