The controlled production of a local hot spot in supercompressed deuterium + tritium fuel is examined in details. Relativistic electron beams (REB) in the MeV and proton beams in the few tens MeV energy range produced by PW-lasers are respectively considered. A strong emphasis is given to the propagation issues due to large density gradients in the outer core of compressed fuel. A specific attention is also paid to the final and complete particle stopping resulting in hot spot generation as well as to the interplay of collective vs. particle stopping at the entrance channel on the low density side in plasma target. Moreover, REB production and fast acceleration mechanisms are also given their due attention. Proton fast ignition looks promising as well as the wedged (cone angle) approach circumventing most of transport uncertainties between critical layer and hot spot. Global engineering perspectives for fast ignition scenario (FIS) driven inertial confinement fusion are also detailed.
X-ray photoelectron spectroscopy (XPS or ESCA), is an analytical technique for chemical surface studies. Used in research, development and manufacturing, this technique is able to obtain the chemical composition of various material surfaces up to 10 nm depth. It is possible to find out if this material is superficially oxidised, or for instance if it contains iron, or carbon. Most of the elements can be detected except hydrogen. Qualitative and quantitative analysis can be performed with a relative precision of 5 % using elemental sensitivity factors. With a detection limit of about 0, 1 % atomic concentration, XPS is a no destructive technique. XPS can also be combined with Argon sputtering to obtain concentration profiles and information on internal interfaces and layers.
Very sensitive to the chemical environment, XPS is a nice tool to study surfaces of ceramics and glasses. Oxygen binding energy shifts give insight into the variations of the ionic/covalent character of oxides and oxide glasses. However in some cases it can be misleading to relate directly the binding energy shifts to changes of the oxygen charge, because Madelung effects can be important and act in the opposite way. Therefore, interpretation of binding energy shifts may benefit from ab initio electronic structure calculations of charge and Madelung energies, when these can be performed (crystalline solids with known structure). Aqueous alteration of ceramics and glass surfaces is a topic where the ability of XPS to distinguish between different chemical environnements, is useful: studying cation photoelectron lines before and after alteration allow detecting changes in the cation (uranium, cerium) oxidation states.
The construction of the Laser Megajoule is scheduled for the end of 2008. A first step is the construction of a prototype named LIL for "Ligne d'Integration Laser" which consists of a complete laser bundle of 8 beamlets. The LIL facility, completed at the beginning of 2002, will be equipped with a target chamber in order to qualify the beam quality and performances on a target and to start laser-plasma experiments at the beginning of 2003. The LIL building, is completed and the installation of laser components started in 2000. In order to meet the project schedule, the construction of the LMJ building now under design will take place at the end of 2002.
The-hydrogen equation of state, and its isotopes deuterium and tritium, is a crucial quantity, to design inertial confinement fusion experiments and is at the heart of the comprehension of astrophysical objects such as giant planets or brown dwarf stars. Recent experiments using the Nova laser at the Lawrence Livermore National Laboratory have shown that deuterium under a,pressure of 1 Mbar could be much more compressible than expected. We will review,here some recent experimental and theoretical aspects of the equation of state in connection with the Nova experiments and with the quest of metallic hydrogen.
The development of high-energy, high-power ultrashort (less than or equal to1ps) laser pulses in the. 1 TW - 1 PW range, has initiated a number of studies on the interaction mechanisms between a laser and a plasma at very high intensities. In this new regime, a large fraction of the laser energy is transferred to ultra short bunches of collimated relativistic electrons. Dragged by these electron jets, a number of protons or heavier ions can also be accelerated inside as well as outside the target. Moreover, the propagation of these electrons in targets of different types gives rise to powerful sources of x-rays and gamma-rays, and to a large number of nuclear reactions. These interactions can result in the emission of neutrons, positrons, and in the production of nuclear isotopes and other types of particles. The characteristics of these new sources, as their short duration and high power, could lead to new applications in different fields.
photoelectron spectroscopy has been used to control the efficiency of a polymer fluorination procedure, designed to produce a layer impermeable to the organic compounds contained in gasoline. Analysis of the different environments of carbon showed the presence after treatment of -CHF-groups attached to -CF2-groups, and the amounts of these groups have been quantified. The presence of CF3 end groups has also been detected, suggesting breakage of the polymer chains during fluorination. ton beam erosion during XPS analysis provides information on the thickness of the fluorinated layer. The lack of improvement in the polymer performance in permeation tests is probably due to the low thickness of the layer and the presence of short chain fragments.
The control of parametric instabilities plays an important role in laser fusion. They are driven by the incident laser beams in the underdense plasma surrounding a fusion capsule and hinder the absorption process of incident laser light which is necessary to heat the fusion target.,Due to its high intensity and power, the laser light modifies the plasma density dynamically, such that two or more parametric instabilities compete, in particular stimulated Brillouin scattering and the filamentation instability. The complicated interplay between these parametric instabilities is studied in detail by developing an adequate model accompanied by numerical simulations With multidimensional. codes. The model is applied to generic and to smoothed laser beams,, which are necessary to limit parametric instabilities, with parameters close to experimental conditions.
In this paper, we present the use of the XPS to resolve some industrial subjects. We have defined a methodology to the systematic use of the XPS in industry to control or to optimize a process or to analyze a defect. Some automotive examples are used to illustrate the capability of this technique to expertise laboratory samples or assembly line samples and samples which come from customers. These examples show the improvement of macroscopic properties is obtained from the most finest material investigation.
From the ionisation of a hot plasma, the X-ray radiation emitted or absorbed is predicted : scheduling research or application experiments can be performed from simple principles. The calculation of a X-ray spectrum of a low-Z or high-Z element, and the various simplifications usually applied are explained. Two examples of applications to plasma diagnostics by X-ray emission or absorption are given.
XPS has become an unavoidable tool for the characterization of the surface properties of materials and particularly of heterogeneous catalysts that hold a strategic position in chemical industry. After a short remind of the catalysis concept some general aspects of this analysis technique are addressed. In this field of application several domains can be distinguished and some are discussed here by way of examples. They deal with the evaluation of the acid-base properties of sulphated zirconia, titania and zeolites, the characterization and optimization of active phases in hydrotreatment catalysis, the support textural effect on activity and selectivity of Fischer-Tropsch catalysts, the NO adsorption-dissociation process on metals and oxides. Besides increasing sensitivity of detection the use of the synchrotron radiation facilities for XPS catalysts studies ensures significant steps toward better spatial and time resolution.
X-Ray Photoelectron Spectroscopy (XPS) is a major technique for the characterization of metal surfaces. It is very sensitive to the first atomic layers, where surface transformation processes occur. The initiation stages of reaction of a material surface with its environment are of particular interest for the research in physical-chemistry. XPS core level peak intensities, emitted by the different elements on the surface, can be used to obtain quantitative information on the outermost layer composition of the materials. Indeed, on metallic materials, XPS can be successfully applied to the study of alloy surfaces, thermal surface segregation of impurities, to gas/solid adsorption phenomena, to the initial stages of metal oxidation at different temperatures, passive layers, atmospheric corrosion of metals, metal coatings and corrosion inhibitors. This review presents these different aspects, with various examples taken from published data.
The plasma conditions obtained in ICF facilities are very close from conditions of some astrophysical plasmas, like stellar interiors. Thus physical processes which are studied in this astrophysical context are relevant for warm and dense laboratory plasmas. This is the case for opacity studies and more specificaly for the line shapes. In this paper I will present qualitatively the physical processes which gore tex the line broadening. Selected exemples will illustrate the similarities between the two disciplinary areas.
Biocompatibility of implants is fundamental. Actual trends lead to osseoinduction inside bone substitutes by associating osteo-progenitors cells from the patient to the biomaterial. This concept implies immobilization of bioactive molecules onto the material surface and verification of the stability of their biological activity in course of time. X-Ray Photoelectron Spectroscopy (XPS) is a very interesting tool to follow the different grafting steps of the biomaterial surface. A RGD (Arg-Gly-Asp)-containing peptides sequence, identified as promoting the attachment of cells, is grafted onto a commonly used hydroxyapatite and characterized by XPS.
I Considerable progress has been achieved in X-ray laser research over the last ten years. Extremely high-brightness sources, having high monochromaticity and partial coherence, are now routinely generated in the 5-50 nanometer spectral range. In this paper, we summarise the physical bases and the experimental context connnected with the generation of X-ray lasers from dense and hot plasmas. We present an overview of the research carried out in France and in other countries, aiming at improving the existing X-ray lasers, exploring alternative routes and developing the use of X-ray lasers sources as a research tool for various applications.
This paper gives a short description of the physical principle and main characteristics of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).
An effective potential approach allows to include the quantum mechanical effects and eliminate the short range divergence. In a plasma, it high temperature, when the De Broglie length is larger than the Landau,length, it is necessary to introduce quantum mechanics. For two point-like electrical charges, without screening, the effective potential is calculated. In the case of a pair of electrons, the exchange effects are taken into account. Expansions with respect to the separation distance r and to a quantum parameter are given. In the limit cases (high temperature, r = 0), the known results are verified. Approximate expressions are proposed. These effective potentials replace the Coulomb potential in. calculations of classical, statistical mechanics to study plasmas. The thermodynamic functions are evaluated.
Petroleum industry is interested in polyethylene as a promising material for designing containers and pipes destined to contain or convey oil products because of their chemical insensitivity to oil by-products, their high resistance to corrosion, and their low cost of production. Nevertheless polyethylenes suffer from a severe drawback: they lack impermeability to gasoline components. X-ray photoelectron spectroscopy has been used to control the efficiency of a polymer fluorination procedure, designed to produce a layer impermeable to the organic compounds contained in gasoline. Analysis of the different environments of carbon showed the presence after treatment of -CHF- groups attached to -CF{sub 2}- groups, and the amounts of these groups have been quantified. The presence of CF{sub 3} end groups has also been detected, suggesting breakage of the polymer chains during fluorination. Ion beam erosion during XPS analysis provides information on the thickness of the fluorinated layer. The lack of improvement in the polymer performance in permeation tests is probably due to the low thickness of the layer and the presence short chain fragments. (A.C.)
