On Plasma Bullet Behavior

Dynamics of atmospheric-pressure plasma plumes have recently attracted significant attentions. However, the nature of the ldquoplasma bulletrdquo behavior is still not clearly understood. The plasma bullets have some feature of a cathode-directed streamer. However, there are several notable differences between the streamerlike plasma plumes and the cathode-directed streamers. One of the differences is the repeatability (reproducible in time and space) of the two types of the discharges. All reports on the plasma bullet behavior suggested that the plasma bullets are very repeatable. This feature is different with that of the cathode-directed streamers, which are typically unrepeatable due to the stochastic nature of their initiation. In this paper, a simple plasma jet device is used to study the plasma bullet behavior. It is found that, when the applied voltage is 8 kV or lower, the plasma bullets are not repeatable. On the other hand, when the applied voltage is 9 kV or higher, they are very repeatable. This characteristic is similar with that of the cathode-directed streamer discharge.