Spectroscopic Measurement of Arc‐Discharge Argon Plasma Plume Injected into Water

Abstract

The electron temperature and the density of argon arc plasma plume injected into water were observed through optical emission spectroscopic measurement. Argon arc plasma jets were generated with a DC arc current of 40–200 A by a non‐transferred arc discharge plasma torch under atmospheric pressure, and ejected through a nozzle on the anode into water or gas‐phase argon. The electron temperature of the plasma plume was determined by the Boltzmann plot with line intensity measurement of atomic argon lines, while the electron density is examined with the Stark broadening measurement of Hα line. It was found that the electron temperature increased from approximately 6500–8000 K, and the electron density also increased up to the order of 1016cm−3, as the discharge current increased for the underwater argon arc plasma plume, both of which were observed at 20 mm in the downward direction from the plasma generator nozzle. In addition, the electron temperature of the underwater plasma plume was slightly lower than that of the gas‐phase argon plasma plume, while the electron density of the underwater plasma was slightly higher than that of the gas‐phase plume. Longitudinal variation of the electron temperature and density of the underwater plasma plume was also observed, and the lowering rate was found to depend on the arc discharge current. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.