Features of electric field distribution along helium atmospheric plasma jet in stepwise propagation mode of guided streamer

A non-uniform distribution of the electric field along an atmospheric pressure helium plasma jet has been determined using the Stark spectroscopy technique at the stepwise propagation of a guided streamer in a free plasma jet and in the jet interacting with a grounded dielectric target. The plasma jet with guided streamers in the stepwise propagation mode is generated by tailoring applied voltage bunches consisting of a superposition of microsecond bipolar square pulses and damped oscillations. The guided streamer head stops at the oscillating voltage falling slope and then propagates further on the next raising voltage front. The electric field distribution along the jet reflects the dynamics of streamer propagation. The electric field strength decreases at a streamer propagation stagnation phase. The field strengthening at the subsequent raising voltage front accelerates the guided streamer at the second propagation step. Graphical abstract