[en] This work aims at measuring the equation of state of porous plastic materials in the view of their use in inertial confinement fusion. We have experimentally determined the shock polar curve of TMPTA (C₁₅H₂₀O₆) by the use of the impedance matching technique. This technique is based on the simultaneous measurement of the shock velocities in the 2 materials composing the target. The shock polar curve has been drawn for pressures ranging from 10 kbar to 3 Mbar and densities from 20 mg/cm³ to 1.1 g/cm³. The use of a slit sweep camera to assess the propagation of the shock wave through the target has limited the accuracy of the technique to 10%. Experimental results match well data provided by the Sesame tables that are broadly used by hydrodynamic codes. Nevertheless the statistical distribution of experimental points seems to show a lower compressibility of the foam that might be attributed to a slight pre-heating process or to the effect of the foam micro-structure on the shock wave propagation. In order to improve the accuracy of the method, an attempt was made to use an active doppler interferometric diagnostic to measure shock wave velocities. It has been showed that the shock wave front in the foam is reflecting enough to make this method relevant if we can overcome the difficulty of a high luminous background. Despite that, we have succeeded in measuring with high accuracy, a point of the shock polar curve for 800 mg/cm³ dense TMPTA. (A.C.)

[en] Concepts of time elapsing 'in' a space measuring the real emerge over the centuries. But Kant refutes absolute time and defines it, with space, as forms reacting to Newtonian mechanics. Einstein and Minkowski open a 20th century where time is a dimension, a substratum of reality 'with' space rather than 'in' it. Kaluza-Klein and String theories then develop a trend of additional spatial dimensions while de Broglie and Bohm open the possiblity that form, to begin with wave, be a reality together 'with' a space-time particle. Other recent theories, such as spin networks, causal sets and twistor theory, even head to the idea of other 'systems of dimensions'. On the basis of such progresses and recent experiments the paper then considers a background independent fourfold time-form-action-space system of dimensions

[en] CaS and SrS, in particular when doped with divalent europium and/or trivalent cerium, have been extensively studied as phosphor materials. In contrast, surprisingly little is known on the behavior of divalent Yb in both hosts. Therefore we report on the luminescence of divalent ytterbium in calcium sulfide and strontium sulfide. In CaS, an emission peak at 760 nm is found, while in SrS ytterbium emission peaks at a strongly red-shifted 950 nm are found. It is motivated that the former is typical for the common 5d–4f luminescence, while the latter is typical for anomalous divalent ytterbium luminescence. Depending on the excitation wavelength, trivalent ytterbium luminescence can also be observed in both hosts. - Highlights: • Yb²⁺ luminescence in CaS and SrS is reported. • In CaS, normal 5d–4f luminescence is found. • In SrS, red-shifted and broadband luminescence is found, typical for anomalous emission. • This behaviour is explained in terms of the position of the 5d level relative to the conduction band

[en] The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UV-visible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO₃OH(H₂O)₂. In summary, the speciation of heptvalent technetium has been investigated in sulfuric acid. In 12 M H₂SO₄, a yellow solution is observed, and its ⁹⁹Tc NMR spectrum is consistent with a heptavalent complex. The yellow solution was further characterized by EXAFS spectroscopy, and results are consistent with the formation of TcO₃(OH)(H₂O)₂. No technetium heptoxide or sulfato- complexes were detected in these conditions. The molecular structure of TcO₃(OH)(H₂O)₂ has been optimized by DFT techniques, and the structural parameters are well in accordance with those found by XAFS spectroscopy. The experimental electronic spectra exhibit ligand-to-metal charge transfer transitions that have been assigned using TDDFT methods. Calculations demonstrate the theoretical electronic spectrum of TcO₃(OH)(H₂O)₂ to be in very good agreement with the experimental one. Recent experiments in 12 M H₂SO₄ show the yellow solution to be very reactive in presence of reducing agents presumably forming low valent Tc species. Current spectroscopic works focus on the speciation of these species.

[en] The structure–property relationships of bulk CeO_2 and Ce_2O_3 have been investigated using AM05 and PBEsol exchange–correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO_2 and Ce_2O_3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. Lastly, the present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

[en] Numerical studies show that a rugby-shaped hohlraum for indirect drive laser ignition has some advantages: it allows a better symmetry for the X-ray irradiation of the central target and it required less laser power. Rugby-shaped cavities have been tested successfully at the Omega facility. The energetic advantage is all the more important as the cavity is bigger. Simulations have shown that a rugby-shaped hohlraum plus adequate materials for the intern wall plus an optimization of the central target could open the way to an ignition with only 160 laser beams at the LMJ (Megajoule Laser) facility. (A.C.)

[en] Probing matter at very high temperatures and pressures requires to use X-ray sources or energetic particles, coupled with high-performance detection systems. Many applications of such sources, developed with high-power lasers are discussed, after recalling their specific operating made and basic physical principles. Concerning the photon sources, these applications are about X-ray radiography, either in the kJ-ns regime, for example for the analysis of imploded targets or the development of hydrodynamic instabilities, or in the ultrahigh intensity (UHI) regime, for the analysis of objects of high surface mass or the XANES spectroscopy using an ultrashort betatron probe. Concerning the particle sources, the significant applications are the protonographic imaging of underdense plasmas, and the isochoric heating of thin targets resulting from the acceleration of electrons by UHI lasers. (authors)

[en] In this work, two different atomic models (ANALOP based on parametric potentials and IDEFIX based on the dicenter model) are used to calculate the opacities for bound-bound transitions in hot dense, low Z plasmas, and the results are compared to each other. In addition, the ANALOP code has been used to compute free-bound cross sections for hydrogen-like ions

[en] We present an experimental study devoted to measuring the opacity of bound-bound transitions in ultra-dense, hot, low Z plasmas, which are at the extreme limit for conditions of both emission spectroscopy and absorption spectroscopy. In this work, we develop an absorption spectroscopy experiment specially adapted to high-density diagnostics, using newly designed structured targets and an ultra-high resolution spectrograph. An aluminum plasma is chosen as the first candidate and the opacity of the He-like 1s²-1s2p (Heβ) and 1s²-1s3p (Heγ) transitions are measured

[en] The adsorption of atomic and gaseous chlorine on Zr (0001) surface has been investigated using state-of-the-art density functional theory calculations as part of an effort to gain fundamental understanding of chlorination processes occurring in fuel cladding materials. Zirconium alloys, including Zircaloy-4, Zircaloy-2 and Zr-Nb alloys (Zirlo^TM and Zr-2.5Nb) are the most common fuel cladding materials in nuclear light water reactors (LWRs) due to their favorable mechanical properties, corrosion resistance, low thermal-neutron capture cross section and criticality. The United States produces a large amount of cladding material from used nuclear fuel, which could approach 1,000 MT/year in the next 50 years. In nuclear fuel recycling, spent nuclear fuel assemblies are disassembled and the cladding hulls are separated from the U oxide spent fuel. Zr can be recovered from Zr cladding using the chlorination method. However the presence of impurities in the recovered ZrCl₄ was reported, including Sn, Cr and Fe. Thus, further efforts are necessary to improve the purification process significantly. This requires fundamental understanding of chlorination processes in cladding materials. Most of the material properties are expected to be similar between the pure zirconium and its alloys due to the fact that the alloy composition consists of more than 95 weight-percent zirconium and less than 2% of tin, niobium, iron, chromium, nickel and other metals. Therefore, while the overarching goal is to understand the chlorination process occurring in complex fuel cladding materials, chlorination of pure zirconium was used as an initial system for the modeling and simulation efforts in this study