Spatiotemporal evolution of a single-electrode nanosecond pulsed microplasma jet over water

Abstract

Biomedical applications, in particular, the application for root canal disinfection, have motivated fundamental studies of single-electrode microplasma jets. In this work, a single-electrode nanosecond pulsed microplasma jet and its interaction with liquid water are evaluated via spatiotemporal optical emission spectroscopy as well as nanosecond gated imaging. The helium microplasma jet was generated in atmospheric air by delivering 8 kV, 164 ns pulses at a pulse repetition rate of 500 Hz. When the microplasma jet impinged on water surface, the spatiotemporal optical emission spectroscopy identified a number of reactive plasma species including O∗, OH∗, He∗, N2∗, N2+∗, and H α ∗. The presence of liquid water produced an approximately 10 times increase in the optical emission intensity compared to water not being present. As such, the presence of water has led to a significant increase in OH radical concentrations. Nanosecond gated imaging showed that the radius of the plasma plume varied with time between the nozzle and the water surface and presented a different propagation behavior from those in air.