Study On Propagation Properties Of Terahertz Wave In Atmospheric Pressure Plasmas

As a hot topic among plasma, electromagnetic field and wave, communication field, the interaction between electromagnetic wave and plasma plays a fairly important role in radio communication, space exploration, plasma electromagnetic wave diagnosis. Atmospheric pressure plasma can discharge in atmosphere and do not need vacuum apparatus. It has short free path between particles and violent discharge process. Depend on these advantages, atmosphere pressure plasma has been widely concerned in recent years. A lot of papers about atmospheric pressure plasma diagnosis jump to our eyes, but most of them were on the limit of electron density around 1017 m-3. For those plasma which electron density up to 1022 m-3,such as arc discharge plasma, there is still no ideal diagnostic method or plenty of experimental measurement. Since then, this paper will try to propose a new method of the plasma diagnosis method. Based on the interaction between high density atmospheric pressure plasma and terahertz wave, such as resonance, absorption, and so on, we will combine the numerical simulation with experiment to study the change of terahertz wave’s transmittance, reflectance, and other parameters. All of them can help us diagnosis atmospheric pressure plasma.Based on dielectric barrier discharge plasma and arc discharge plasma, this paper starting from the most commonly used theoretical simulation, the sandwich structure model of the plasma, study the propagation properties of terahertz wave in the different density and dielectric constant of the atmospheric pressure plasma,analyze terahertz wave’s reflection coefficient and transmission coefficient. Using ANSYS FLUENT software to simulate the arc discharge, combined with Saha equation, calculate the related parameters of arc discharge plasma.Do some experiments on arc discharge plasma and dielectric barrier discharge by the terahertz laser which can output 1.63 THz, 2.53 THz and 3.11 THz steadily.Through the analysis of numerical simulation and experimental results, found that the interaction between Atmospheric pressure plasma and incident terahertz wave is obvious when the plasma frequency at terahertz frequencies. If the electron density below 1020m-3, such as dielectric barrier discharge plasma, terahertz wave’s transmittance up to 0.99 and the wastage rate is rather low when it incidences. So the terahertz wave diagnosis method is suitable for high density atmospheric pressure plasma. This research provides new ideas on arc plasma high density plasma diagnosis.