Lettre ouverte à Lexis-Nexis : à propos de l’édito de M. Jean Hauser « Phéromones »

Ce texte est une réponse rédigé par plusieurs juristes en réaction à un édito publié dans la Semaine juridique et portant sur le harcèlement sexuel. Il analyse et dénonce les propos tenus dans cet édito comme étant porteurs de stéréotypes de genre et d'une banalisation des violences sexuelles.This text is an answer written by several jurists to react to an editorial about sexual harassment published by the French legal review Semaine juridique. It analyses and denounces this editorial witch conveys gender stereotypes and trivialise sexual violence

On the possibility of ultrafast Kossel diffraction

We discuss the possibility of realizing time-resolved Kossel diffraction experiments for providing indications on the crystalline order or the periodic structure of a material. We make use of the interaction of short, ultra-intense laser pulses with a solid target, which generates short bursts of hot electrons. Penetrating inside a layered sample (i.e., a crystal or an artificial multilayer material), these electrons ionize inner-shell electrons so that the subsequent radiative filling of K-shell vacancies results in a strong Kα emission that is enhanced in the Bragg directions corresponding to the period of the material. We present simulations of angle-resolved Kα emission, which displays so-called Kossel patterns around the Bragg angles. We then discuss possible experiments appropriate for laser facilities delivering short and intense pulses

On the possibility of ultrafast KOSSEL diffraction

International audienceWe discuss the possibility of realizing time-resolved Kossel diffraction experiments for providing indications on the crystalline order or on the periodic structure of a material. We make use of the interaction of a short, ultra-intense laser pulses with a solid target which generates short bursts of hot electrons. Penetrating inside a layered sample (i.e. a crystal or an artificial multi-layer material), these electrons ionize inner-shell electrons so that the subsequent radiative filling of K-shell vacancies results in a strong Kα emission which is enhanced in the Bragg directions corresponding to the period of the material. We present simulations of the angle-resolved Kα emission which displays the so-called Kossel patterns around the Bragg angles. Then, we discuss possible experiments appropriate for laser facilities delivering short and intense pulses

Etude experimentale et modelisation theorique de l'emission X et de l'emission spontanee amplifiee X-UV des ions neonoiedes dans un plasma cree par laser

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Stark–Zeeman line-shape model for multi-electron radiators in hot dense plasmas subjected to large magnetic fields

International audienc

Stark-Zeeman line shape model for multi-electron radiators in hot and dense plasmas submitted to large magnetic fields

We present a Stark-Zeeman spectral line shape model and the associated numerical code, PPPB, designed to provide fast and accurate line shapes for arbitrary atomic systems for a large range of plasma conditions. PPPB is based on the coupling of the PPP code, a Stark broadened spectral line shape code, developed for multi-electron ion spectroscopy in hot and dense plasmas, and the MASCB code, recently developed to generate B-field dependent atomic physics. The latter provides energy levels, statistical weights and reduced matrix elements of multi-electron radiators by diagonalizing the atomic Hamiltonian which includes the well know B-dependent term. They are used as input in PPP working in the standard line broadening approach, i.e. using the quasi-static ion and impact electron approximations. The ion dynamics effects are introduced by the mean of the frequency fluctuation model (FFM). The physical model of the electron broadening is based on the semi-classical impact approximation including the effects of a strong collision term, of interference and cyclotron motion. Finally, to account for polarization effects, the output profiles are calculated for a given angle of observation with respect to the direction of the magnetic field. The potential of such model is presented through Stark-Zeeman spectral line shape calculations performed for various experimental conditions

Self-seeding of SASE-soft-X-ray FEL using artificial Bragg reflectors

The use of artificial Bragg reflectors in double-crystal non-dispersive configuration and backscattering geometry is proposed to achieve the self-seeding of SASE-soft-X-ray FEL. It is shown that the proposed system verifies the set of criteria given by J. Feldhaus et al. [Opt. Commun. 140, 341 (1997)]. Owing to the short duration of the x-ray pulses, the problem of reflection and self-seeding is discussed in the time-domain

Etude de l'influence de l'environnement plasma sur les sections efficaces d'excitation collisionnelle électron-ion dans un plasma chaud et dense

Les sections efficaces d'excitation collisionnelle sont des ingrédients essentiels dans la modélisation des propriétés radiatives d'un plasma hors équilibre thermodynamique. Dans le cas où le système électron-ion peut être considéré comme isolé, diverses méthodes quantiques issues de la théorie de la diffusion existent pour traiter correctement ce problème. Dans un plasma dense, on s'attend à ce que les particules voisines perturbent considérablement ces transitions. La modélisation du plasma par l'intermédiaire d'un potentiel perturbateur purement radial a déjà été effectuée, mais elle n'est pas satisfaisante pour les excitations collisionnelles car elle ne parvient à rendre compte ni de la levée de dégénérescence des niveaux ni de ses conséquences. Nous avons levé la "symétrie sphérique" en introduisant le microchamp électrique quasistatique produit par les ions voisins. Cette étude théorique inédite nous a permis de réaliser un code numérique, calculant automatiquement les forces de collision et taux collisionnels d'ions complexes de manière précise (Distorted Waves) en présence d'un microchamp reproduisant fidèlement la réalité. Nous avons appliqué cette étude au cas de l'Aluminium hydrogénoïde et héliumoïde. La prise en compte du microchamp électrique sur les sections efficaces d'excitation collisionnelle fait apparaître notablement les transitions issues d'états de moment angulaire élevé. En particulier, les sections efficaces de transitions interdites en l'absence de microchamp augmentent de plusieurs ordres de grandeur en sa présence et deviennent de l'ordre de celles des transitions autorisées. Nous avons, en outre, réalisé un code collisionnel-radiatif stationnaire élémentaire pour évaluer l'influence de ces modifications sur les profils de raies correspondants. L'importance de l'effet précédent n'élargit, cependant, que légèrement les raies de couche K.Collisionnal excitation cross-sections are essential to modeling of out of equilibrium plasmas radiative properties. Many quantum resolutions of scattering have been successful in the treatment of isolated electron-ion systems. But in dense plasmas, neighbouring particles are expected to widely disturb these transitions. Plasma modeling through a radialy perturbated potential has already been done but is not satisfactory as it doesn't account for levels degeneracy breaking and its consequences. Introduction of quasi-static electric microfield of neighbouring ions has allowed us to break spherical symmetry. Our original theoretical study has given birth to a numerical code that accurately computes collisionnal strengths and rates (distorted Waves) submited to a realistic microfield. Hydrogen- and Helium-like Aluminium has been studied. Stark mixing widely increases rates of transitions from high l levels and forbidden transitions are field-enhanced of many orders until they reach allowed ones. Eventually, we wrote an elementary stationary collisionnal-radiative code to watch field-enhancement effects on corresponding fine shapes. Yet, the wide previous enhancement little broadens K-shell lines.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Collisional-Radiative modeling and radiative emission of tungsten in tokamak plasmas in the temperature range [800-5000] eV

We present new collisional-modeling calculations of tungsten plasmas at electron density of about 5 × 1013 cm−3 and for electron temperatures in the range 0.8–5 keV. These conditions are relevant to current tokamaks. In this temperature range, the modeling of the ionization balance and of spectra is a long-standing problem. Addressing this problem is also useful for plasmas that will be produced in the future tokamak ITER. In particular, we discuss the problem of ensuring completeness of the list of configurations included in the calculations. We also discuss comparisons of experimental measurements in the EUV range performed in the WEST tokamak with synthetized spectra based on the use of the unresolved transition array and of the spin–orbit split array formalisms. While this work does not rely on a precise identification of detailed lines, modeled spectra display emission features that looks quite similar to the experimental spectra. A conclusion is that standard calculation methods used for the evaluation of the configuration average collisional and radiative rates, are fine provided that a convenient list of configurations is used in the calculations

Modeling of the interaction of an x-ray free-electron laser with large finite samples

We describe a model for the study of the interaction of short X-ray Free-Electron Laser (XFEL) pulses with large finite samples. Hydrodynamics is solved in one-dimensional planar geometry with consideration of the electron-ion energy exchange and of the possible elasto-plastic behavior. From a time-dependent calculation of the complex refractive index and of the underlying atomic physics, XFEL energy deposition is modeled through a calculation of the radiation field in the material. In the case of hard X-ray irradiation, energetic electrons induced by the XFEL absorption can propagate and deposit their energy outside the interaction region. Simulations of the interaction of hard X-ray ultrashort pulses with solid materials Ru and Si at different grazing incidence angles are presented and discussed. The results obtained demonstrate the potential of this approach to predict damage dynamics for materials of interest for X-ray optics