Dynamics of Plasma Bullets in a Microsecond-Pulse-Driven Atmospheric-Pressure He Plasma Jet

In this paper, an atmospheric-pressure helium plasma jet driven by a home-made microsecond pulse generator was studied. The discharge was characterized by monitoring the voltage-current waveforms and head-on/side-on intensified charge coupled device (ICCD) images. The effects of gas flow rate and pulse frequency on the plasma bullet propagation were studied. The plasma bullets showed a donut shape in the beginning of discharge and then became solid. This was due to the curling up of the plasma plume. A smaller gas flow rate was beneficial for a homogeneous discharge and a higher bullet peak velocity. The pulse frequency had no influence on the bullet peak velocity, but a higher frequency induced a faster bullet speed decay.