Opacity calculations in X and XUV range using a detailed atomic code

Abstract

Calculations of accurate opacities in X and XUV range are of high interest for several domains such as astrophysics or inertial fusion science. Such quantities may be investigated through laser-plasma interaction in the indirect-drive scheme. In this work absorption properties of such plasmas are analysed using the Flexible Atomic Code. Detailed and unresolved-transition-array modes are investigated, and some results obtained with the mixed mode recently developed are also proposed. For a carbon plasma the present approach agrees with the results obtained with the superconfiguration code SCO. Some results are provided about the X-ray opacity of nickel, and a comparison with data from a recent campaign on LULI 2000 facility is done. This comparison demonstrates that the Unresolved Transition Array approach may be insufficient, e.g., to determinate the accurate position and shape of the 2p-3d structure in nickel at about 25 eV. The case of non-electric-dipole-type transitions, such as magnetic dipole transitions is addressed. The electric-dipole and magnetic-dipole transitions are studied here in the case of the 3 * n complex of five tungsten ions, with charge states similar to those found in the tokamak divertors. It is demonstrated that the unresolved transition array formulas provide a fairly accurate description of the most important absorption structures, but fail to reproduce correctly the behavior of the opacity in the wings of these main structures.

Simultaneous X-ray and XUV absorption measurements in nickel laser-produced plasma close to LTE

“…Additionally, a hybrid mode has been recently developed where some levels are dealt with in detail (fine-structure) while others are averaged through the transition array formalism [52]. The data produced by FAC are post-processed using a code recently developed [53]. As a rule, the UTA/SOSA mode of FAC allows one to perform atomic computations faster by orders of magnitude than the detailed mode.…”

“…This effect of a spectator 4 × 1 electron is discussed in the Appendix A. The bound-bound contribution is computed using a newly implemented hybrid mode of FAC [53]. The configurations involved in the 2p-3d line, including the 4 × 1 spectator electron are treated as detailed, while all the other configurations are in UTA mode.…”

L-Mn dielectronic recombination of cerium ions in a room-temperature EBIT

“…where p e is electron momentum, g i , The (FAC, [28]) was used for calculations in UTA mode. This mode uses a relativistic configuration average approach known as spin orbit split array, explained in more detail in [29,30], to calculate the electronic structure. By skipping the angular momentum couplings and grouping the full detailed fine structure into relativistic sub-configurations, the UTA mode significantly reduces the number of intermediate and final states by more than an order of magnitude.…”

“…Therefore, further within this article the results of cross section calculation for particular charge state and electron energy regime were scaled, without specifying the scaling parameters, to facilitate comparison with the experimental results. The UTA mode has been benchmarked by several groups comparing UTA-based opacity and emissivity spectra with full detail fine structure calculations [29,31] for a wide range of elements and charge states. FAC also includes the sub-configuration averaged distorted wave method to apply the distorted wave approximation to the UTA-configuration-average wave functions, providing collisional ionization cross-sections [32,33].…”