Studies On The Open-M-Shell Opacities Of Mid-Z Plasmas Using Detailed Line Accounting Models

A detailed term accounting model and a detailed level accounting model have first been developed in our country to study the open M-shell opacities and the temperature diagnostics in plasmas of medium-Z elements. The following paragraphs will describe the main results of the present works:1. In the present detailed term accounting (DTA) model, the massive atomic data are obtained by using the multiconfiguration Hartree-Fock (MCHF) method with Breit-Pauli relativistic corrections. Extensive configuration interaction (CI) has been included in LS coupling scheme to obtain energy levels and the bound-bound transition cross sections. In the calculation of the line broadening, the Doppler width and electron impact width are considered and the Voigt function are applied to account for the line profile. Detailed configuration accounting is applied to calculate the bound-free absorption cross sections. The free-free absorption is taken into account by the Kramers formula, and the Thomson scattering cross section is taken in the calculation of the photon scattering by free electrons. In the case of local thermodynamic equilibrium, the ionization balance in plasmas is obtained by solving the Saha equation and the level populations are determined by the Boltzmann statistical distribution. The ionization potential depression (IPD) of an ion in hot dense plasmas is evaluated by the Stewart-Pyatt model.2. A detailed level accounting model is developed, and the massive atomic data are obtained by the full relativistic Dirac-Fock equation. Only configuration interaction within one-configuration is considered to reduce the scale of the CI matrix. To improve the efficiency, the GRASP code is parallelized in the environment of message passing interface (MPI) and the parallel efficiency is linear with the number of the computing nodes used in calculations.3. The hot dense sodium fluoride (NaF) plasma is taken as an example for the first systematical and detailed comparisons among the main theoretical models developed in our country. In the case of p = 0.01 g/cm3, T = 40 eV and the case of p = 0.01 g/cm3, T = 50eV, both spectrally resolved opacities and mean opacities of NaF plasmas are calculated by the detailed term accounting model, unresolved transition array model, detailed configuration model and average atom model. The results show good agreements both in the line positions and the absorption structures. In the detailed comparisons, good agreements are found among the various models in the case of T = 40 eV, but differences appear for the Planck mean opacities when the temperature increases to 50 eV. An important reason is that the charge state distributions calculated by those models have large discrepancies at T = 50 eV. At such temperature, more electrons can be striped off the sodium and fluorine atoms than that of T = 40 eV, the number ofabsorption lines has large differences among nearby charge states in the plasma, and therefore the radiative opacity becomes more sensitive to the charge state distribution under such condition.4. The radiative opacities of iron plasmas are first studied by the present detailed term accounting model, and extensive CI calculation are found having obvious effects on the radiative opacities. The experimental transmission spectrum [G. Winhart et al, Phys. Rev. E 53, R1332(1996)] of an iron plasma is studied. In contrast to the single HF method applied in the OPAL code, the present studies show that the strong CI can effectively change the oscillator strengths and therefore having better agreements with experiments. Another experimental transmission spectrum of an iron plasma [P. T. Springer et al, J. Quant. Spectrosc. Radiat. Transf. 58, 927(1997)] is simulated by the present DTA model, and good agreements are found. The iron opacities for an isothermal sequence of T - 20 eV are studied to show the effects of the line width to the Rosseland opacity.5. The experimental transmission spectrum [Jiamin Yang et al, Phys. Plasmas 10, 4881(2003)] of a hot aluminum plasma is simulated using the present DTA model. The line ratio between the absorption lines of Al X and Al XI are studied to determine the temperature in the aluminum sample. After the studies on the discrepancies between the measured spectrum and the detailed simulation, it is concluded that the experimental transmission spectrum was probably obtained mainly at the temperature of about 65 eV but overlapped by some lower temperature spectra of even down to 35 eV. The relative strength of the fine absorption lines within one charge state cannot be reproduced accurately without considering the non-Boltzmann distribution among the energy levels of the ion.6. The experimental transmission spectrum of a hot bromine plasma [J. E. Bailey et al., J. Quant. Spectrosc. Radiat. Transf. 81, 31(2003)] is simulated at the first time using the present detailed level accounting model and the major features of the experimental data are well reproduced. The line overlapping of each bromine ions in the 2p → 3d absorption region is shown and identified. The temperature of the bromine sample is diagnosed by the present DLA model via the analysis of the line ratios of different charge states in the 2p → 3d transition groups and gives the temperature within ± 1 eV uncertainty. The DLA calculation also shows that the 2p1/2→ 3d3/2 absorptions are over estimated by the statistical models. The openM-shell opacity of a hot bromine plasma is studied by both the AA model and the present DLA model. Good agreements are found for Planck mean opacity but differences of the line positions exist in the 2p → 3d absorption lines due to the statistical treatment for the one-electron orbitals in AA model. It is suggested that the AA model should take the charge state distribution into account.7. A preliminary study is performed on the experimental transmission spectrum [T. S. Perry et al., Phys. Rev. E 54, 5617(1996)] of a hot niobium plasma using the present DLA model. Discrepancies are found between the experimental and the theoretical results about the 2p → 3d line positions and absorption strengths. Comparisons with other theoretical results show that accurate line positions are needed to identify the ion, who contributes more to the absorptions.8. The temperature diagnostic of an iron plasma is performed in the super extra ultraviolet (XUV) energy region. In this region, the absorption lines of different charge states have strong overlapping to each other so that the temperature is determined by the global fitting of the experimental spectrum instead by the detailed line ratios.9. A recent measurement of the charge state distribution and the radiative transmission of Fe/NaF plasma mixture [M. E. Foord et al, Phys. Rev. Lett. 93, 055002(2004)] are studied using the present DLA model. The measured charge state distribution of in the iron plasma was well reproduced in the case of local thermodynamic equilibrium, but discrepancies are found in the populations of the sodium and fluorine ions. Good agreements are obtained between theoretical and experimental transmission spectrum, which confirm the measured charge state fractions in the iron plasma.