Non-LTE kinetics modeling of krypton ions: Calculations of radiative cooling coefficients

Abstract

For plasmas containing high-Z ions the energy loss due to radiative processes can be important in understanding energy distributions and spectral characteristics. Since high-Z plasmas occur over a wide range of temperature and density conditions, a general non-LTE population kinetics description is required to provide a qualitative and quantitative description for radiative energy loss. We investigate radiative properties of non-LTE krypton plasmas with a collisional–radiative (CR) model constructed from detailed atomic data. This work makes two extensions beyond previous non-LTE kinetics models. First, this model explicitly treats the dielectronic recombination (DR) channels. Second, this model allows one to investigate the higher electron density regimes found commonly in laboratory plasmas. This more comprehensive approach enables the study of population kinetics in a general manner and will provide a systematic guide for reducing a complex model to a simpler one. Specifically, we present the calculations of radiative cooling coefficients of krypton ions as a function of electron density in the optically thin limit. Total, soft X-ray (1.6 keV ≤ E ≤ 12 keV), and hard X-ray ( E ≥ 12 keV) radiative cooling coefficients are given for the plasma conditions of 0.6 keV ≤ T e ≤ 10 keV and 10 14 cm −3 ≤ N e ≤ 10 24 cm −3. The ionic radiative cooling coefficients provided are sufficient to allow users to construct the total rate from given charge state distributions. Steady-state calculations of the average charge state at given T e and N e values are also presented.