Electrical and plasma characteristics of nanosecond-pulse surface discharge under varying pressure

Plasma flow control, based on plasma aerodynamic actuation (PAA), has become a newly-rising focus of international aerodynamic and thermodynamic fields. Nanosecond-pulse surface discharge is considered to be a new way of generating plasma aerodynamic actuation. When it comes to the practical application, the altitude at which plasma flow control is expected to be adopted is about 10-20km, where the static pressure is only 40-185 Torr, and it is much lower than atmospheric pressure. In this paper, with a three-electrode plasma sheet actuator, the electrical and plasma characteristics of nanosecond-pulse surface discharge are experimentally investigated under varying pressures. A RO4350B (high frequency circuit material, Rogers) plate with the thickness of 1 mm and relative permittivity constant of 3.48 is taken as the dielectric layer of the plasma sheet actuator. The discharge pattern changes from dielectric barrier discharge to sliding discharge when the pressure is under 200Torr. As the pressure decreases from 760 Torr to 5 Torr, N₂(C³Π_u) vibrational temperature decreases slightly at first and then increases remarkably. With the pressure of about 80 Torr, the change of discharge mode from a filamentary type to a glow type has been observed. In the filamentary mode, the electron temperature hardly changes, while in the glow mode, the electron temperature increases obviously with the decrease of pressure.