Characteristics of atmospheric pressure Ar/H₂O plasma jet discharge

To promote the applications of atmospheric pressure plasma jet(APPJ) in Ar/H₂O mixtures in material surface modification, plasma medicine, and environmental engineering, etc., we investigated the discharge modes and some parameters of the APPJ in Ar/H₂O. We measured the electrical, light-emission and spectral characteristics of this APPJ induced by different applied voltages, and hence calculated the pattern of some main discharge parameters such as discharge power, transported charge, electron excitation temperature, molecule vibrational temperature, and rotational temperature varying with applied voltage. The results show that, with increasing applied voltage, the discharge process of APPJ in Ar/H₂O can be divided into three phases, namely, corona discharge, dielectric barrier discharge(DBD), and jet discharge, which can be distinguished easily by voltage-current waveforms and light-emission images. The main species produced by APPJ in Ar/H₂O includes Ar and OH, as well as a small amount of O and N₂. With increasing applied voltage, the discharge power, transported charges, and spectrum intensity of the main species (including OH) all increase. In addition, when the applied voltage rises from7 kV to 9.5 kV, the electron excitation temperature and rotational temperature also increase from 1 000 K to 2 200 K and from 350 K to 550 K, respectively, and the excitation temperature of electron is 0.646 eV under the applied voltage of 9.5 kV.