Behaviors of Plasma Bullet Propagation and Effects of Gas Flow Rate

An Ar dielectric-barrier-discharge atmospheric-pressure plasma jet (APPJ) driven by a 34-kHz sinusoidal power source is employed to investigate plasma bullet propagation in positive and negative half cycles by using an intensified charge-coupled device camera. The effects of different Ar gas flow rates on plasma bullet behavior are also presented in this paper. It is found that the duration and velocity of bullets in a positive discharge current pulse are significantly shorter and faster than those in a negative discharge current pulse and APPJ seems easier to form the plasma bullet phenomena during the positive discharge current pulse. The differences between positive and negative discharge current pulses can be explained by using the cathode-directed streamer and negative corona theories, respectively. It is considered that, due to the possible turbulence flow, the propagation length of plasma bullets is decreased with the increment of gas flow rates.