Effects of sheath gas flow on He atmospheric pressure plasma jet

It was demonstrated that employing a sheath gas flow was effective in the formation of long laminar flow of He jet without turbulence by matching the gas velocities at the boundary between the He core jet and the N2 sheath gas flow. With the extension of He laminar flow, the plume length of plasma was significantly extended to more than 20 mm at a 0.5-slm flow rate of He. The irradiation area for the direct plasma treatment of the target was clearly limited within 2 mm even at a 10-mm distance from the target.