International audienceA model is developed that permits the calculation of the radiation emitted by complex or highly charged ions in a plasma. The model is based on the usual separation of the plasma-emitter interaction into the homogeneous broadening effects of the fast electrons and the inhomogeneous broadening arising from slow ions. For plasma conditions where the ion motion can be neglected, the spectrum is the usual static line shape. To account for ion dynamics, the frequency-fluctuation model is introduced by decomposing the line shape of each radiative transition into a sum of radiative channels that are associated with the smallest observable inhomogeneities that form the static profile. The fluctuations of the ion microfield, the ion dynamics effect, is modeled by an exchange process between the static radiative channels. This results in both a smoothing and an overall coalescence of the radiative channels and depends strongly on an averaged characteristic fluctuation rate associated with the dynamics of the interaction of the local plasma microfield with the ion. This rate is formally related to the double-time field-field correlation function behavior. This stochastic model of the observed frequency fluctuations permits fast and accurate calculations of the emitted spectral profiles, including ion dynamics emitted by complex ions in a wide range of plasma conditions

A very fast method to account for charged particle dynamics effects in calculations of spectral line shape emitted by plasmas is presented. This method is based on a formulation of the frequency fluctuation model (FFM), which provides an expression of the dynamic line shape as a functional of the static distribution of frequencies. Thus, the main numerical work rests on the calculation of the quasistatic Stark profile. This method for taking into account ion dynamics allows a very fast and accurate calculation of Stark broadening of atomic hydrogen high- n series emission lines. It is not limited to hydrogen spectra. Results on helium- beta and Lyman- alpha lines emitted by argon in microballoon implosion experiment conditions compared with experimental data and simulation results are also presented. The present approach reduces the computer time by more than 2 orders of magnitude as compared with the original FFM with an improvement of the calculation precision, and it opens broad possibilities for its application in spectral line-shape codes.

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A model for calculating the profile of spectral lines emitted by multielectron emitters in a hot plasma is described. The Stark broadening is included in the model by using the static ion approximation and an impact approximation for the electrons. The atomic data required for the line-shape calculation are extracted from an atomic structure code and prepared as data necessary for the excited and ground levels of the radiative transition. For the cases where electron broadening is much smaller than the average ionic Stark shift, an approximation is proposed to obtain rapidly a diagonal form of the evolution operator for the emitter. Line shapes of lithiumlike and berylliumlike ions have been calculated under the conditions of recent experiments performed in laser-produced plasmas.

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A computer simulation technique is used to calculate hydrogen spectral lines emitted by a plasma. These calculations are used to study ion dynamic effects on the line profiles. Results are obtained for Lyman-a, Lyman-P, and Lyman-y lines, and comparisons are made with experimental results and with other theoretical methods.

A single positive ion is imbedded in an electron gas with overall charge neutrality. A classical statistical mechanics is considered using an electron-ion Coulomb potential regularized at distances within the de Broglie length. The electron charge density and electric field distribution at the ion are studied as a function of ion-electron coupling using molecular dynamics simulation and theoretical models. Agreement between theory and simulation is quite good in general, although differences are observed for very strong ion-electron coupling due to the enhanced importance of close electron-ion configurations.

A very fast method for calculating line shapes in the presence of an external magnetic field accounting for charge particle dynamics is proposed. It is based on a reformulation of the frequency fluctuation model, which provides an expression of the dynamic line shape as a functional of the static distribution function of frequencies. In the presence of an external magnetic field, the distribution of intensity and polarization of the emission depends on the angle between the observation line and the magnetic field's direction. Comparisons with numerical simulations and experimental results for various plasma conditions show very good agreement. Results on hydrogen lines in the context of magnetic fusion and the Lyman-α line, accounting for fine structure, emitted by argon in the context of inertial fusion, are also presented.