Spatio-temporally resolved electric field measurements in helium plasma jet

The focus of this paper is on the spatially and temporally resolved measurements of the electric field in atmospheric-pressure plasma jets operating in helium. Using the Stark polarization spectroscopy method, temporal development of the electric field was observed in steps which were in range of 20–500 ns. Such temporal resolution was complemented by the spatial resolution of 0.025 mm. Depending on the plasma jet configuration, the maximal electric field strength in the bullet/streamer head was between 10 and 20 kV cm−1. Electric field measurements are accompanied by the electrical and spectroscopic diagnostics of the discharge evolution. It was found that without the grounded electrode downstream from the nozzle, the jet develops as the cathode directed streamer. Contrarily, when a grounded electrode is present, development of the plasma jet is very similar to the evolution of the single microdischarge in air. Finally, the direct relation between electric field strength and the velocity of the plasma bullet is demonstrated. (fast track communication)