Plasma and Terahertz-Wave Propagation Characteristics in Atmospheric-Pressure Plasma Jet Under Different Operating Conditions

High-density plasma source device is of great significance for ground experiment verification of vehicle reentry communication. atmospheric-pressure plasma jet (APPJ), as a high-density plasma source, has received little attention in ground experiments on vehicle communications. In this article, terahertz (THz) wave propagation characteristics in APPJ are investigated by joint simulation of APPJ discharge and THz transport model and related experimental measurements. THz interferometer (THz-IF) system is used to diagnose the electron density and THz transmission characteristics of APPJ for the first time, and the measured results are in good agreement with the simulation results of a joint simulation model in this article and the measured results of THz time-domain spectroscopy (THz-TDS) system of other researchers. Sheath thickness and electron density produced by self-designed APPJ are highly matched with the plasma sheath environment of the HIFIRE-5b vehicle. Further analysis of the influence of different voltages and needle electrode radius on the THz transmission characteristics shows that the absorption effect plays a major role in THz-wave attenuation in APPJ, and the contribution of the collision effect almost disappears, which is completely consistent with the phenomenon observed in HIFIRE-5b vehicle. The joint simulation model and THZ-IF method developed in this article are of great significance for the ground test verification of reentry communication schemes.