Low-Pressure Jet Rf Discharge in a System With a Liquid (Non-Metallic) Electrode

An experimental study of a jet radio-frequency discharge (1.76 MHz) at reduced pressure in a system with a liquid plasma-forming medium (6% aqueous solution of ((NH)SO) was conducted. Within the range of 1,000 to 80,000 Pa, the morphology and stability of the discharge, as well as its electrophysical, spectral, and thermal characteristics, were investigated. It is shown that as the pressure decreases from near-atmospheric to 20–4 kPa, the discharge transitions from a discrete microchannel structure to an extended truncated conical column. At ∼1 kPa, due to the lowered boiling point and intense vaporization, non-stationary behavior and breakdown dynamics emerge. Current-voltage characteristics were constructed in the form of Lissajous ellipses. Emission spectroscopy and analysis of Stark broadening of the H/H lines were used to determine the electron concentration from the H line. Infrared thermography recorded a local temperature maximum in the jet-plasma interaction zone. The results establish a "passport" of operating regimes and confirm the existence of an energy-efficient pressure range of 20–40 kPa for plasma-liquid applications.