Temporal and Spatial Study of Plasma Bullet and Reactive Species in a Helium Plasma Jet

The temporal and spatial distribution of plasma jet bullets and reactive species in a pulse driven atmospheric pressure helium plasma were studied. Electrical and optical measurements were performed for the plasma bullet distribution under different discharge parameters. Moreover, the behavior of reactive species including He, N₂⁺ and O were obtained. The results show that: 1) Two discharges appear during pulse rise time and pulse fall time, respectively. And the plasma bullets present different shapes. 2) The discharge voltage and pulse frequency have a great influence on plasma bullets behavior. The plasma length and bullet velocity increases with applied voltage, but an overhigh voltage induces turbulence, thus decrease the plasma length. Higher pulse frequency induces a higher bullets velocity and also a more rapid decay rate. 3) The temporal and spatial distribution of N₂⁺ emission is consistent with plasma bullets, which travels to a long distance. While, the He and O emission only locate near the quartz nozzle.