Optical emission spectroscopy diagnostics of inductively-driven plasmas in argon gas at low pressures

An optical emission spectroscopy method for determination of electron temperature, electron density and gas temperature is developed and applied for diagnostics of inductively-driven argon discharges in a cylindrical geometry. The discharges are maintained at frequency 27 MHz, applied power varied in the limits P = (90 – 160) W and gas pressure in the range p = (1.1 – 117.3) Pa. The method combines measurements of emission spectral line intensities and profile broadenings with a collisional-radiative model of argon plasma at low pressure. The model is employed for investigation of the plasma kinetics governing the population densities of 3p54s and 3p54p argon configuration levels, treated separately. In the numerical calculations the electron density and electron temperature are varied whereas the values of the third plasma parameter — the gas temperature — are involved as obtained data from the experiments. Comparison of the experimental results of the line-intensity ratios with those calculated by the model yields the values of the electron density and temperature. The dependence of the electron temperature, electron density and gas temperature on the discharge conditions is obtained and discussed in the study.