Temperature diagnostics for Z-pinches plasma in dependence on compression degree

Calculations of the spectral coefficients for X-ray absorption and spectral brightness's for X-ray radiation were performed for niobium Z-pinch plasma at the temperature of 1 keV and at different plasma densities to determine the compression degree where the spectral lines become indistinguishable. As known, traditional methods of temperature diagnostics of hot dense radiating plasmas are based on analysis of the spectral line shape in dependence on plasma temperature and density. In this case, the interval of photon radiation energies is used, where the spectral lines are well distinguishable in an experiment. On the other hand, Z-pinch plasma has high compression, and an increase of plasma density leads to the deformation of the spectral line shape because of Doppler broadening, Stark broadening, and so-called “additional” broadening of spectral lines that take place in a quantum statistical ensemble of plasma ions and atoms. The traditional method of temperature diagnostics becomes impossible and different methods, which do not use spectral line characteristics, should be applied. The aim of this paper is to determine the density border where the spectral lines become indistinguishable. Important features of the quantum mechanical model, which is known as ion model of plasma, and which is used for calculations in the presented paper, are considered and discussed. A brief review of the theoretical models that have been earlier developed to calculate the radiative opacity characteristics of hot dense plasma is presented as well.