[en] The magnetic properties of [Fe(20 A)/Ag(t)]₂₀ superlattices with Ag film thickness varying from 7 to 20 A, prepared by molecular beam epitaxy on (0 0 1)MgO substrate, are presented. The epitaxial growth and the quality of layered structure of the samples were controlled by RHEED and X-ray diffraction techniques. Magnetic hysteresis loops with the magnetic field applied parallel and perpendicular to the plane of the films were determined by vibrating sample magnetometer and superconducting quantum interference device (SQUID) magnetometer at 4.2 K. Magnetotransport properties were measured by conventional DC four terminal method with the magnetic field applied parallel to the plane of the films at 4.2 K. The analysis of the hysteresis loops indicates an in plane easy magnetization axis and shows a dependence of the interface anisotropy on the Ag film thickness

[en] Microanalysis possibilities have been explored to determine light element concentrations within glasses (melt inclusions and basaltic glass fragments) and volcanic phenocrysts. In the first step, C was examined. The study of different spectral interferences lead to calculated detection limits of 40 μg/g for basaltic glasses and 50 μg/g for olivine crystals. The C contents of all investigated specimens range from 40 μg/g (the detection limit) to 6800 μg/g. Heterogeneities were revealed within glass inclusions. Measurements show obvious concentration profiles in basaltic glass samples. Our results agree with previous published data and are reliable. Accuracy of measurements is about 20%. 12 refs

No abstract available

[en] The knowledge of the fissile material mass is a key challenge to enhance radioactive waste management and to ensure a high level of safety in nuclear industry. Data is analyzed according to the principles of the neutron measurement techniques. As proportional counters filled with ³He gas display high neutron detection efficiency and a good gamma-ray discrimination, they are the reference detector for passive neutron coincidence counting. A charge preamplifier or a current amplifier, depending on applications, collects the electric pulse produced by neutron interaction in the ³He gas and a threshold discriminator produces a logic pulse used for neutron counting. This paper describes the performance assessment of different commercially available electronics from Mirion Technologies, Precision Data Technology (PDT), Mesytec, as well as MONACO electronics originally developed by CEA LIST for fission chamber measurements in experimental reactors. Comparative passive neutron measurements are carried out with these electronics at CEA/DEN Nuclear Measurement Laboratory in Cadarache. Overall, PDT and Mesytec electronics show similar detection efficiency as the ACH-NA98 charge amplifier, which is commonly used in our laboratory for such applications. However, MONACO electronics have a lower detection efficiency, similar to Mirion 7820 current amplifier used in specific high-count rate applications. An optimisation of MONACO settings would probably be necessary to adapt to ³He counters instead of fission chambers.

[en] An important aspect of quantitative fluid inclusion analysis using X-ray emission techniques concerns a knowledge of fluid inclusion depth and geometry to establish reliable absorption correction procedures. The aim of this study is to assess the potential performance of the nuclear reaction ²³Na(p, p^'γ)²³Na in estimating inclusion depth. Na was chosen because of its common occurrence in natural fluids. The nuclear reaction displays a characteristic, low energy resonance peak at 1.283 MeV in its cross-section which, together with recognition that the energy of the incident particles traversing matter decreases predictably with depth, allow estimation of the thickness of quartz traversed by the beam and hence the inclusion depth. Results of the calculation shows accuracy on estimated fluid inclusion depths commonly better than ±0.5 μm. In addition, following the same experimental protocol as defined for Na, we show how the use of the elastic scattering reaction ²⁸Si(p, p)²⁸Si can provide information on the fluid inclusion thickness

[en] Proton-induced X-ray emission (PIXE) and light element analysis have been performed with the nuclear microprobe at the Laboratoire Pierre Suee (Saclay-France) in glass inclusions of the carbonaceous chondrites: Allende, Kaba and Renazzo, and in the achondrite meteorite: Chassigny. Carbon contents in olivine of chondrules are below the nuclear reactions analysis (NRA) detection limit, however, glasses from glass inclusions hosted by these grains, contain an appreciable and highly variable quantities of carbon (200-1600 ppm). This could indicate variable amounts of C trapped during glass inclusion formation. On the other hand, nitrogen is present in highly variable amounts in glasses of both, chondrites and achondrites minerals. Its abundance, correlated with depth from the section surface which suggests loss of N during analyses and therefore the possible existence of a very mobile (volatile?) species. A chondritic Rb/Sr and K/Rb ratio obtained by PIXE analyses in the glass-bearing inclusions of the Chassigny meteorite points towards a primitive source for the glass precursor of Chassigny inclusions

[en] Alpha emitters are usually identified and quantified by alpha spectrometry measurements in a vacuum chamber performed in laboratory environments. This study shows that transuranic elements can be distinguished under ambient conditions using a grid collimator. The aim of this work was to use numerical simulations with the MCNP6 code to design a grid with a resolution high enough to differentiate the same radionuclide combinations as alpha spectrometry in a vacuum chamber, namely ²³⁹Pu + ²⁴⁰Pu, ²⁴¹Am + ²³⁸Pu and ²⁴⁴Cm. Results show that a compromise is required to obtain the best performances in terms of energy resolution and detection efficiency, leading to the choice of two hexagonal grid collimators. The first has a collimation height of 0.5 cm and an apothem of 1 mm. Laboratory tests on electrodeposited sources show that the target radionuclides can be identified without prior deconvolution, with an energy resolution of about 70 keV and a detection efficiency of 0.74% at incident energies of 5–6 MeV. The second grid has the same collimation height but a coarser mesh with an apothem of 2 mm. In this case, the alpha peaks are still distinguishable, but with a lower resolution of 125 keV. The detection efficiency is three times higher however. Key words: Ambient conditions / In situ alpha spectrometry / Monte-Carlo simulations / Nuclear waste / Radiological characterization

[en] Micron-sized melt inclusions (MI), trapped in host quartz crystals from rocks of magmatic systems, probe the evolution of ore deposits. PIXE in combination with NRA of light element concentrations provide a nearly complete database for geochemical characterisation. Tin deposits are usually associated with highly fractionated granitic magmatism. The tin porphyry deposits of Bolivia however have only a moderately fractionated bulk rock geochemistry. The investigation of MI revealed high degrees of fractionation with compositions similar to tin granites. It is supposed that the bulk rock geochemistry must be interpreted as the product of magma mixing. Unexposed granitic portions, represented by MI, provide magmatic vapour phases for hydrothermal alteration and mineralisation

[en] The nuclear microprobe enables the localization and the quantitative determination of all elements from hydrogen to uranium using atomic and/or nuclear methods: PIXE, PIGE, RBS, ERDA, NRA, STIM, etc. These methods and the apparatus required are shortly described. Three examples show that complementary information is obtained by nuclear microprobe analysis and NAA. The first example is the study of the abnormal behavior of metallic impurities during the purification of metallurgical grade silicon by directional solidification. This behavior is due to the presence of silicon carbide micro-precipitates at the bottom of the ingots. The second example concerns the determination of trace element (Ni, Mn, Rb, Sr) partition coefficients between a solid phase (mineral) and a liquid phase (lava-glass inclusions). These determinations enable the specification and modelling of the processes which govern the magma evolution in volcanological contexts. The third example deals with the study of trace elements in archeological bones. Using PIXE, PIGE, NRA and NAA, it is possible to correlate the concentrations of some elements, such as C, N, F, and Zn in the femoral diaphyse with both the age, the pathology and diagenetic mechanism of the human being at the moment of death. (author)

[en] Fluorine quantitative microanalysis was performed on geological samples, using the ¹⁹F (p, p'γ) ¹⁹F reaction, with a 30 μm proton microbeam at an energy of 3.4 MeV. We have detailed the analytical procedure and the calibration method in relation to a large range of fluorine concentrations in natural glasses and some minerals. This procedure was applied to study the fluorine distribution in melt inclusions trapped in minerals of different origins. The potential of this nuclear microanalysis method is discussed. (orig.)