Search

A collisional?radiative model is developed for population calculations of plasmas in non-local thermodynamic equilibrium. The rate equations in detailed configuration accounting are solved to obtain ion populations. The configuration averaged rate coefficients are used in the rate equations. The cross sections are calculated based on the first perturbation theory. Wavefunctions required in cross section calculations are obtained by the Hartree?Fock?Slater self-consistent-field model. This kinetic model is applied to low- and medium-Z as well as high-Z plasmas. The results are compared with those of other theoretical models and experiments. The comparisons show that the present results of the mean charge state for low- and medium-Z elements agree well with other theoretical ones, while for high-Z elements, the present mean ionization stages are about two stages lower than the experimental ones.

A model is developed to calculate the emission spectrum of non-local thermodynamic equilibrium (LTE) plasmas. The collisional-radiative model is adopted for non-LTE population calculations. Configuration-averaged rate coefficients that are needed in the rate equations are obtained based on the first-order perturbation theory. The Hartree-Fock-Slater self-consistent-field method is used to calculate electron wavefunctions. The present model is applied to the calculation of isoelectronic line-ratio of Cr and Ti, which is useful for plasma electron temperature diagnosis.

Using a detailed configuration accounting model with term structures treated by the unresolved transition array model, we have extensively investigated the opacities of mixture materials. For plasmas at the temperature of 250 eV and density of 1 g/cm3, our calculated Rosseland mean opacities are in good agreement with other theoretical results. A high increase in the Rosseland mean opacity to 2944 cm2/g is achieved for a multi-element mixture compared to the value of 1729 cm2/g for pure gold. Various mixtures at other plasma conditions are also studied.

A programme is developed to calculate the polarizations of the radiation emitted after electron impact excitation. The fully relativistic distorted-wave method is used in cross-section calculations. The programme is applied to He- and Li-like ions. The calculated values of line polarization are compared with other theoretical results and experimental values. For He-like U, at lower incident energy, the present polarization agrees with the other theoretical ones within 1%, while at higher energy, the differences increase up to about 10%. For He-like Fe and Ti, the present results of polarization degree for most of the lines agree with the experimental data within the experimental error bars. For the Li-like Ti line q (1s2s2p2P3/2 to 1s22s), the present value of the polarization agree excellently with another theoretical one, and both the values are consistent with the measured data within the experimental error bar.

A method is presented to calculate the spectral-resolved opacity for non-local-thermodynamic-equilibrium plasmas. With the present method, the configuration population is obtained by solving the rate equations within the framework of configuration-averaged approximation in which the cross sections are calculated based on the first-order perturbation theory. The transition properties are calculated by using the unresolved transition array model. As the illustration, the frequency-dependent opacities of Al and Au plasmas are calculated and compared with the simulation results of the super configuration collisional radiative code. General agreements are obtained and there are some discrepancies for opacity of high-Z elements.

Based on the average atom model, a non-local thermodynamic equilibrium (non-LTE) model is developed to calculate opacity for mixtures. This model could be applied to high-Z problems. The mean ionization degrees of SiO2 of the present calculation are slightly higher compared with another model for mixtures. As an example, the opacity of Au and Nd mixture is calculated. The results show concrete non-LTE effects and the increase in opacity of the mixture is shown clearly.

Based on the detailed configuration accounting model (DCA), a method is developed to calculate the rate of the resonant photoionization (RP) in the average atom (AA) model. Using this method, the RP rates are calculated for an average ion and compared with DCA calculation. The comparison shows the reasonableness of the proposed method. The RP process is included in the AA rate equations and the numerical results show that RP can cause an additional ionization up to 10% or so in some cases.

The formulae of photon angular distribution and polarization degree for radiative recombination are presented to include the contribution of multipoles and their correlations. A fully relativistic code is then developed to calculate the photon angular distribution and polarization. The calculated polarization degree and differential cross-sections agree well with that of Scofield's results within 10%. The effects of multipoles on polarization and angular distribution are investigated. The polarization and the angular distribution become asymmetric when the multipoles are accounted as the electron energy increases.