Diagnostics of absorbing inhomogeneous plasmas by spectral line emission

The paper is devoted to diagnostics by optical emission spectroscopy of inhomogeneous plasmas, which cannot be considered as optically thin. The consideration is limited with steady plasmas close to local thermal equilibrium. The distribution of plasma temperature along the observation direction has one maximum and a monotone fall around it. Numerical modelling has been performed to find the relations between the plasma opacity and spatial distribution of thermodynamic parameters, from one side, as well as intensity and spectral profiles of atomic lines in the plasma volume emission, from another side. Argon plasma at atmospheric pressure and its atomic emission spectra have been chosen for the modelling. Stark broadening has been supposed to determine local line profiles. The relations obtained allow evaluating absorption and inhomogeneity rates of the plasmas by spectral line profiles in the volume emission. Also, the plasma temperature can be determined using relative intensity of spectral lines in the plasma volume emission. recorded directly and after its reflection by an auxiliary mirror behind the volume. The modelling results show the technique feasibility, its application range and error limits.