Opacity calculations of low Z plasmas for ICF

Abstract

In this work we analyze the behavior of Pl anck and Rosseland mean opacites of carbon plasmas in a wide range of temperature and densities to propose si mple analytical expressions for these quantities. Carbon is one of the most interesting elem ents under investigation, since it is likely to be a major plasma-facing wall component in ITER, and it plays a major role in inertial fusion scenarios. The opacity data are computed under the detailed-level-accounting approach through the use of the code ABAKO/RAPCAL a kinetic code developed by our research group based in a collisional-radiative steady state model covering corona, NLTE and LTE situations. This code has been successfully tested comparing its results with other proven codes in the fourth and fifth Kinetic Code Comparison Workshops. It also has demonstrated to be useful for diagnostic of experiments as it is described in an oral pr esentation in this conference. 2. Method of calculation In this work we have performed a detailed analysis of the mean opacity for Carbon plasma, using high quality atomic data obtained using the code FAC (1). This code provides atomic magnitudes calculated into the DLA approach, using appropriate coupling schemes and including configuration interaction. The calculation of ioni c charge state distributions and level populations are performed by means of solving the Saha-Boltzmann equations for LTE and a collisional-radiative steady-state model (CRSS) for NLTE cases. The level populations are computed with a reasonable accuracy for plasmas of any element in a wide range of conditions embracing non-LTE, LTE and CE situations. In this paper we have restricted ourselves to LTE cases. The multifrequency opacity is obtained as a sum of the bound-bound, bound free, free-free and scattering contributions.