S. Ferri

Ground work supporting the codes based upon the frequency fluctuation model

The development of the frequency fluctuation model (FFM) had two strong motivations. First, there was interest to model line shapes accounting for ion dynamics and second the inclusion of higher order radiative processes in plasmas was considered important for future development. The FFM relies on the hypothesis that the emitter-plasma system behaves approximately like a pseudo-molecule embedded into a thermal bath. As a result, the pseudo-system can be considered to have internal states connected to each others by collisions with the bath. This simple starting point has been translated into a powerful renormalization process, called FFM, resulting, a few years ago, in a fast line shape code called Pim Pam Poum (PPP) and more recently into a code for the computation of radiative redistribution. The authors present a few of the milestones in this evolution.

Strongly coupled laser produced plasmas: investigation of hollow ion formation and line shape analysis

Abstract X-ray line emission originating from hollow ions has been identified in dense laser-produced plasmas by means of two-dimensional X-ray optics and spectral simulations performed by the code MARIA. It is shown that for plasma coupling parameters Γ >1 excited states correlation effects of hollow ion configurations exceed the usual ground-state population channel by many orders of magnitude. The intensity of the emission of these excited-state hollow ions can be stronger than those of the usual satellite or resonance line transitions and lead to a remarkable distortion of the spectral emission. Detailed spectral simulations for the K-shell spectral interval are carried out for the 1s2l n l′-Rydberg configurations as well as the K 1 L 0 M 1 N 1 , K 1 L 0 M 1 N 0 O 1 , K 1 L 0 M 1 N 0 O 0 P 1 hollow ion configurations. Population kinetics, Stark broadening and spectral analysis are discussed along with experimental results of silicon laser-produced plasmas.

Ionization potential depression for non equilibrated aluminum plasmas

A classical molecular dynamics simulation model, designed to simulate neutral plasmas with various charge states of a given atom together with electrons, is used to investigate the ionization potential depression (IPD) in dense plasmas. The IPD is discussed for aluminum plasma at and out of equilibrium. The simulation results are compared with those of earlier theoretical models and with experimental data obtained in the framework of x-ray free-electron laser experiments. The model proposed in this work appears as an important tool to provide data for further discussion on IPD models.

Discussion of the validity of binary collision models for electron broadening in plasmas

Abstract Recent plasma spectroscopic investigations of line profiles indicate that conditions can be obtained where a usual electron collision operator is unable to describe the entire line profile. This situation arises for plasma conditions when the interactions with electrons is a major broadening mechanism and the quasi-static electron, or non-binary, effects are important. As examples we find that this is the case for high- n hydrogen lines over a wide range of electron densities and low- n hydrogen lines at higher electron density. A solution has been proposed for high- n hydrogen lines by using a frequency-dependent electron broadening operator accounting for some overlapping of the impact and the non-binary regimes. The domain of validity of different approaches that attempt to including many-body dynamical and statistical effects will be discussed and compared with numerical simulations.

Electric micro fields in simulated two component plasmas.

The statistical properties of local electric fields in an classical plasma are investigated by molecular dynamics (MD) simulation. Two‐component plasma simulations of neutral hydrogen, protons and electrons for intermediate plasma coupling conditions, typically Ne≈1018cm−3, Te≈1eV, have been carried out. These simulations appear as a possible and very useful way to generate relevant microfield sample‐sets appropriate for ion emitter lineshape simulations for plasma spectroscopy and to provide guidance for line shape modeling.

Improved Frequency Fluctuation Model for Spectral Line Shape Calculations in Fusion Plasmas

A very fast method to calculate spectral line shapes emitted by plasmas accounting for charge particle dynamics and effects of an external magnetic field is proposed. This method relies on a new formulation of the Frequency Fluctuation Model (FFM), which yields to an expression of the dynamic line profile as a functional of the static distribution function of frequencies. This highly efficient formalism, not limited to hydrogen‐like systems, allows to calculate pure Stark and Stark‐Zeeman line shapes for a wide range of density, temperature and magnetic field values, which is of importance in plasma physics and astrophysics. Various applications of this method are presented for conditions related to fusion plasmas.

MD and FFM Electron Broadening for Warm and Dense Hydrogen Plasmas

Direct integration of the semi‐classical evolution equation based on Molecular Dynamics simulations (MD) and the Frequency Fluctuation Model (FFM) have long been used to synthesize spectra accounting for ion dynamics. Cross comparisons of these approaches generally show results in good agreement. Recently, interest in low temperature (Te ∼ 1eV) and high density (Ne ∼ 1018 cm−3) hydrogen plasma spectroscopy has motivated extended applications of FFM. Arising discrepancies were found to originate in electron collision operators suggesting an improper use of impact approximations for warm and dense plasma conditions. In order to clarify this point, new useful cross comparisons between MD and FFM have been carried out for electron broadening.

Frequency fluctuation model survey

Developed since the late eighties the frequency fluctuation model line shape code (today called PPP, formerly PimPamPoum) is recognized as a flexible fast and accurate state of the art plasma spectroscopy tool altogether with a powerful link between charge dynamics theory in hot and dense matter and spectroscopy.

Models for Stark broadening applied to plasma diagnostics

For the case of line shapes dominated by Stark broadening several models have been recently developed with the aim of being used in line shape codes valid for a wide range of plasma conditions. Several of these models are described, and their results are compared to experimental results. Plasma conditions are identified for which the standard Stark broadening approximations are not valid.

A modern Fizeau experiment for education and outreach purposes

On the occasion of the lasers 50th anniversary, we performed a modern Fizeau experiment, measuring the speed of light with a laser beam passing over the city centre of Marseille. For a round trip distance of almost 5 km, the measurement has reached an uncertainty of about 10?4, mainly due to atmospheric fluctuations. We present the experimental and pedagogical challenges of this brilliant outreach experiment.