Development of the guiding channel of plasma bullets in N₂

Plasma bullets are commonly observed when an atmospheric pressure plasma jet is excited by kHz voltages. These fast moving volumes of plasma are basically streamers guided by the remnants of previous discharges, resulting in a repeatable discharge channel on the jet axis. Since the guiding mechanism is a memory effect based on previous discharges, there must be a development phase when the first bullets are generated. We investigated the development of the guiding channel for a pulsed plasma jet in N₂ by individually recording the discharges at the first voltage pulses with an ICCD camera. We found that it takes approximately 2 ms (around 7 voltage pulses) to fully develop the guiding channel. Additionally, comparing this to a numerical simulation of the flow field shows that the development is related to the distance traveled by the remnants in the gas flow.