Electron Temperature Measurement of Atmospheric-pressure Non-equilibrium Ar Plasma by Line Intensities with CR Model and by Continuum Emissivity

Atmospheric-pressure non-equilibrium plasmas are being applied to various practical fields. The objective of this study is to examine their electron temperature $T_e$ of Ar DBD plasma with several methods of optical emission spectroscopy (OES) measurements, i.e., with line-intensity measurement and with continuum emission measurement. With the help of Ar collisional-radiative (CR) model of low-temperature argon plasma of atmospheric pressure, the relationship between $T_e$ and the excitation temperature $T_{ex}$(4p-5p) of 4p-5p levels is numerically surveyed over some ranges of the electron density and the gas temperature. It is found that $T_e$ is uniquely determined with the parameter $T_{ex}$(4p-5p) under low $T_e$ conditions. Consequently, $T_e$ of the DBD plasma is estimated to be about $0.6 - 1.0$ eV. Meanwhile, $T_e$ is also determined by the OES of continuum spectrum due to the Bremsstrahlung, where the Maxwell and Druyvesteyn electron energy distribution functions (EEDFs) are assumed for the theoretical analysis of the OES data. It is found that the latter EEDF gives reasonable results that agree well with the line-intensity OES measurement with the Ar CR model. Future possibility to find the EEDF of this kind of plasmas is briefly discussed.