W/SiC x-ray multilayers optimized for use above 100 keV

We have developed a new depth-graded multilayer system comprising W and SiC layers, suitable for use as hard x-ray reflective coatings operating in the energy range 100-200 keV. Grazing-incidence x-ray reflectance at E = 8 keV was used to characterize the interface widths, as well as the temporal and thermal stability in both periodic and depth-graded W/SiC structures, whereas synchrotron radiation was used to measure the hard x-ray reflectance of a depth-graded multilayer designed specifically for use in the range E ~150-170 keV. We have modeled the hard x-ray reflectance using newly derived optical constants, which we determined from reflectance versus incidence angle measurements also made using synchrotron radiation, in the range E = 120-180 keV. We describe our experimental investigation in detail, compare the new W/SiC multilayers with both W/Si and W/B4C films that have been studied previously, and discuss the significance of these results with regard to the eventual development of a hard x-ray nuclear line telescope

Hard x-ray characterization of a HEFT single-reflection prototype

We have measured the hard X-ray reflectivity and imaging performance from depth graded W/Si multilayer coated mirror segments mounted in a single reflection cylindrical prototype for the hard X-ray telescopes to be flown on the High Energy Focusing Telescope (HEFT) balloon mission. Data have been obtained in the energy range from 18 - 170 keV at the European Synchrotron Radiation Facility and at the Danish Space Research Institute at 8 keV. The modeling of the reflectivity data demonstrate that the multilayer structure can be well described by the intended power law distribution of the bilayer thicknesses optimized for the telescope performance and we find that all the data is consistent with an interfacial width of 4.5 Å. We have also demonstrated that the required 5% uniformity of the coatings is obtained over the mirror surface and we have shown that it is feasible to use similar W/Si coatings for much higher energies than the nominal energy range of HEFT leading the way for designing Gamma-ray telescopes for future astronomical applications. Finally we have demonstrate 35 arcsecond Half Power Diameter imaging performance of the one bounce prototype throughout the energy range of the HEFT telescopes

Hard x-ray characterization of a HEFT single-reflection prototype

We have measured the hard X-ray reflectivity and imaging performance from depth graded W/Si multilayer coated mirror segments mounted in a single reflection cylindrical prototype for the hard X-ray telescopes to be flown on the High Energy Focusing Telescope (HEFT) balloon mission. Data have been obtained in the energy range from 18 - 170 keV at the European Synchrotron Radiation Facility and at the Danish Space Research Institute at 8 keV. The modeling of the reflectivity data demonstrate that the multilayer structure can be well described by the intended power law distribution of the bilayer thicknesses optimized for the telescope performance and we find that all the data is consistent with an interfacial width of 4.5 Å. We have also demonstrated that the required 5% uniformity of the coatings is obtained over the mirror surface and we have shown that it is feasible to use similar W/Si coatings for much higher energies than the nominal energy range of HEFT leading the way for designing Gamma-ray telescopes for future astronomical applications. Finally we have demonstrate 35 arcsecond Half Power Diameter imaging performance of the one bounce prototype throughout the energy range of the HEFT telescopes

Effects of rare-earth co-doping on the local structure of rare-earth phosphate glasses using high and low energy X-ray diffraction

Rare-earth co-doping in inorganic materials has a long-held tradition of facilitating highly desirable optoelectronic properties for their application to the laser industry. This study concentrates specifically on rare-earth phosphate glasses, (R2O3)x(R'2O3)y(P2O5)1-(x+y), where (R, R') denotes (Ce, Er) or (La, Nd) co-doping and the total rare-earth composition corresponds to a range between metaphosphate, RP3O9, and ultraphosphate, RP5O14. Thereupon, the effects of rare-earth co-doping on the local structure are assessed at the atomic level. Pair-distribution function analysis of high-energy X-ray diffraction data (Qmax = 28 Å-1) is employed to make this assessment. Results reveal a stark structural invariance to rare-earth co-doping which bears testament to the open-framework and rigid nature of these glasses. A range of desirable attributes of these glasses unfold from this finding; in particular, a structural simplicity that will enable facile molecular engineering of rare-earth phosphate glasses with 'dial-up' lasing properties. When considered together with other factors, this finding also demonstrates additional prospects for these co-doped rare-earth phosphate glasses in nuclear waste storage applications. This study also reveals, for the first time, the ability to distinguish between P-O and PO bonding in these rare-earth phosphate glasses from X-ray diffraction data in a fully quantitative manner. Complementary analysis of high-energy X-ray diffraction data on single rare-earth phosphate glasses of similar rare-earth composition to the co-doped materials is also presented in this context. In a technical sense, all high-energy X-ray diffraction data on these glasses are compared with analogous low-energy diffraction data; their salient differences reveal distinct advantages of high-energy X-ray diffraction data for the study of amorphous materials

A New Crystal Bender for the ID31 Laue-Laue Monochromator

International audienceThe ID31 beamline is able to provide X-Ray energies ranging from 20 to 150keV. The energy range 50-150keVis covered by a Laue-Laue monochromator located at 100meters from the source. Two asymmetrically cut Si crystals equipped with benders, based on a new concept, provide an energy resolution ranging from few hundreds of eV down to the Darwin width of few eV. The bender principle, design, manufacture and first commissioning will be described. The virtual source, produced with a white beam transfocator, can be before or after the monochromator. Therefore the bending mechanism must allow both concave and convex configuration with bending radius from 20m to infinite. Each bender is equipped with two home made piezo-jacks in close loop with capacitive sensor. The system is liquid Nitrogen cooled. The thermal behaviour will be described in detail and thermo-mechanical finite element analysis presented

Combined texture and microstructure analysis of deformed crystals by high-energy X-ray diffraction

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Neutron and X-ray diffraction studies of TeCl4 and TeBr4 liquids

International audienceHigh-energy X-ray and neutron diffraction measurements have been carried out on TeCl4 and TeBr4 liquids just above their respective melting points. Both neutron SN(Q) and X-ray SX(Q ) structure factors exhibit a pronounced first sharp diffraction peak (FSDP) at Q1(TeCl4)≈1.2Å-1 and Q1(TeBr4)≈1.1Å-1 indicating a significant intermediate range order in the two liquids. The complementarity between neutrons and X-rays allows the FSDP to be attributed to Te–Te correlations at a characteristic length scale L1 ≈ 2π/Q1 ≈ 5.3–5.7 Å. The total correlation functions TN(r) and TX(r ) show first nearest-neighbor distances at r1TeCl4)≈2.36Å-1 and r1(TeBr4)≈2.54Å-1 in good agreement with a sum of covalent radii for Te, Cl or Br. The Te coordination was found to be nearly tetrahedral, 3.8 ⩽ NTe–X ⩽ 4.0, where X = Cl or Br. A distinct correlation at r2(TeCl4)≈2.75Å and r2(TeBr4)≈2.85Å was attributed to short nearest-neighbor Te–Te contacts. The respective coordination number, NTe–Te ≈ 1, suggests a Te2X8 dimer to be the main structural unit in tellurium tetrahalide liquids, i.e., intermediate between tetrameric Te4X16 solid and monomeric TeX4 gas. This proposed short range order is consistent with intermediate range structure since the average molecular size of elliptic Te2Cl8 (≈5.4 Å) and Te2Br8 (≈5.8 Å) agrees with derived intermolecular separation and periodicity L1

Time-dependent synchrotron X-ray diffraction on the austenite decomposition kinetics in SAE 52100 bearing steel at elevated temperatures under tensile stress

We have studied the decomposition kinetics of the metastable austenite phase present in quenched-and-tempered SAE 52100 steel by in situ high-energy synchrotron X-ray diffraction experiments at elevated temperatures of 200-235 °C under a constant tensile stress. We have observed a continuous decomposition of austenite into ferrite and cementite. The decomposition kinetics is controlled by the long-range diffusion of carbon atoms into the austenite ahead of the moving austenite/ferrite interface. The presence of a tensile stress of 295 MPa favours the carbon diffusion in the remaining austenite, so that the activation energy for the overall process decreases from 138-148 to 82-104 kJ mol-1. Before the austenite starts to decompose, a significant amount of carbon atoms partition from the surrounding martensite phase into the metastable austenite grains. This carbon partitioning takes place simultaneously with the carbide precipitation due to the over-tempering of the martensite phase. As the austenite decomposition proceeds gradually at a constant temperature and stress, the elastic strain in the remaining austenite grains continuously decreases. Consequently, the remaining austenite grains act as a reinforcement of the ferritic matrix at longer isothermal holding times. The texture evolution in the constituent phases reflects both significant grain rotations and crystal orientation relationships between the parent austenite phase and the newly formed ferritic grains.</p

A high-pressure and high-temperature gas-loading system for the study of conventional to real industrial sized samples in catalysed gas/solid and liquid/solid reactions

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