X-ray-ultraviolet beam splitters for the Michelson interferometer

International audienceWith the aim of realizing a Michelson interferometer working at 13.9 nm, we have developed a symmetrical beam splitter with multilayers deposited on the front and back sides of a silicon nitride membrane. On the basis of the experimental optical properties of the membrane, simulations have been performed to define the multilayer structure that provides the highest reflectivity-transmission product. Optimized Mo-Si multilayers have been successfully deposited on both sides of the membrane by use of the ion-beam sputtering technique, with a thickness-period reproducibility of 0.1 nm. Measurements by means of synchrotron radiation at 13.9 nm and at an angle of 45° provide a reflectivity of 14.2% and a transmission of 15.2% for a 60% s-polarized light, close to the simulated values. Such a beam splitter has been used for x-ray laser Michelson interferometry at 13.9 nm. The first interferogram is discussed

X-ray fluorescence induced by standing waves in the grazing-incidence and grazing-exit modes: study of the Mg--Co--Zr system

We present the characterization of Mg-Co-Zr tri-layer stacks by using x-ray fluorescence induced by x-ray standing waves, both in the grazing incidence (GI) and grazing exit (GE) modes. The introduction of a slit in the direction of the detector improves the angular resolution by a factor 2 and significantly the sensitivity of the technique for the chemical characterization of the buried interfaces. By observing the intensity variations of the Mg Kalpha and Co Lalpha characteristic emissions as a function of the incident (GI mode) or detection (GE mode) angle, we show that the interfaces of the Si/[Mg/Co/Zr] x30 multilayer are abrupt, whereas in the Si/[Mg/Zr/Co] x30 multilayer a strong intermixing occurs at the Co-on-Zr interfaces. The explanation of this opposite behaviour of the Co-on-Zr and Zr-on-Co interfacesis given by the calculation of the mixing enthalpies of the Co-Mg, Co-Zr and Mg-Zr systems, which shows that the Co-Zr system presents anegative value and the two others positive values. Together with the difference of the surface free energies of Zr and Co, this leads us to consider the Mg/Zr/Co system as aMg/Co x Zr y bi-layer stack, with x/y estimated around 3.5.Comment: Published in Journal of Synchrotron Radiation 22, 1419 (2015)http://scripts.iucr.org/cgi-bin/paper?S160057751501623

X-ray multilayer monochromator with enhanced performance

International audienceAn x-ray multilayer monochromator with improved resolution and a low specular background is presented. The monochromator consists of a lamellar multilayer amplitude grating with appropriate parameters used at the zeroth diffraction order. The device is fabricated by means of combining deposition of thin films on a nanometer scale, UV lithography, and reactive ion etching. The performance of this new monochromator at photon energies near 1500 eV is shown

Large-field high-resolution X-ray microscope for studying laser plasmas

International audienceIn 1948, P. Kirkpatrick and A. V. Baez developed an x-ray microscope (energy range about 100 eV-10 keV) composed of two concave spherical mirrors working at grazing incidence. That device, named KB microscope, presents a 3-5 μm resolution within a field having a radius about 100 μm; outside that field, its resolution lowers rapidly when the object point recedes from the center. The adjunction of two similar mirrors can notably increase the useful field (typically, the resolution can be better than 10 μm within a 2-mm-diam field of view), which is necessary for studying laser plasmas. Its main advantage with respect to more simple optics, as the pinhole, is that it can be located far enough from the plasma to avoid any destruction during the shot. We describe such a microscope that we call KBA microscope and present some images of fine metallic grids. Those grids were backlighted by x-raysources, either a cw one or a series of laser plasmas from the Octal-Héliotrope facility. Examining the films in detail shows that the experimental results are very close to the theoretical characteristics; hence the interest of this device for the x-raydiagnostics on the future powerful laser facilities

Utilisation du spectre de Fourier des courbes de réflectivité X pour l'étude d'empilements de couches minces

La réflectivité en X rasants est couramnent utilisée pour la caractérisation d'empilements de couches minces. Les paramètres à déterminer sont: épaisseurs, rugosités, et indices. On peut y accéder en ajustant la courbe aexperimentale de reflectivité avec une courbe theorique calculée à partir de ces pamètres (méthode d 'essai-erreur). Une autre méthode consiste à utiliser la transformation de Fourier pour étudier directement les caracteristiques de l'empilement La courbe expérimentale n'étant pas périodique, les données doivent être préalablement traitées avant d'appliquer la transformation de Fourier. A partir d'exemples réels, on montre comment l'analyse deFourrier donne des indications sur le modèle de l'empilement. Les résultats permettent essentiellement d'évaluer les distances entre toutes les interfaces. La précision des réultats depent de la bande passante angulaire de détection. La largeur des pics dans le spectre permet également d'évaluer la rugosité des interfaces relatives au pic. La méthode est limitée par les propriétés liées au caractère discret de la transformée de Fouria. Les résultats sont affinés par la méthode d'essai-erreur précédemment décrite, mais mais partir de parametres déja connus approximativement, ce qui permet de gagner un temps considérable pour l'ajustement des courbes

Miroirs polarisants et non polarisants dans l'UV lointain pour la raie Lyman- de l'Hydrogène (=121,6 nm)

National audienc

Miroirs polariseurs dans l'UV lointain

N°R-S07/SU-0004-23 (2009

Investigation of polarizing mirrors at 121.6 nm

International audienc