Numerical simulation of ionization wave propagation in an atmospheric plasma jet*

Atmospheric pressure plasma jets are one of the typical low-temperature plasma sources. In this study, we developed a two-dimensional numerical model to describe the fluid and discharge behavior of an atmospheric plasma jet using helium gas. The plasma jet consists of a cylindrical quartz tube with a pair of circular metal electrodes. The inner and outer diameters of the quartz tube are 4 mm and 6 mm, respectively, and the distance between the electrodes is 25 mm. A sinusoidal voltage of 6 kV peak and a frequency of 20 kHz is applied to the electrodes. We conducted numerical simulations focusing on the discharge structure, especially on the behavior of ionized waves. The steep increase in the applied voltage (dV/dt) ignites plasma near the powered-electrodes. Ionizing waves travel upward from the electrode toward the open end of the discharge tube, with a maximum propagation velocity of about 50 km/s.