Electrical and optical investigations of plasma bullets driven by different waveforms

In this work, a He atmospheric plasma jet was generated in stable bullet mode by using a dielectric barrier single electrode configuration. The plasma bullets were generated by four different excitation high-voltage waveforms and propagated through a dielectric barrier quartz tube. Corresponding charge, propagation speed and density were evaluated by current monitoring of the bullets, which were flowing through the travelling-bullet tube. It was revealed that positive bullets will be generated with higher current signals, charge, density and propagation speed by an excitation high-voltage waveform having a broader positive width and a greater portion of negative voltage (complex waveform). On the other hand, an excitation high-voltage with negative polarity initiates faster bullets than that of positive polarity. Last but not least, the optical emission spectroscopy results confirmed our electrical diagnostic results, and showed that more active and intense plasma is generated by the waveform with longer positive width and more negative portion.