Search results for "RADIATION"
showing 10 items of 5298 documents
<title>Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy</title>
2007
Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward d…
A study of KNbO3in the pressure range to 12 GPa using synchrotron radiation
1997
Abstract Orthorhombic KNbO3 has been studied by x-ray diffraction as a function of pressure. The lattice cell parameters, volume and stability range of this phase have been determined as a function of the applied pressure. No structural transformation has been observed up to 12 GPa. The resulting P-V data are fitted to a Murnaghan equation state of first-order.
High-energy X-ray diffraction and topography investigation of CdZnTe
2005
High-energy transmission x-ray diffraction techniques have been applied to investigate the crystal quality of CdZnTe (CZT). CdZnTe has shown excellent performance in hard x-ray and gamma detection; unfortunately, bulk nonuniformities still limit spectroscopic properties of CZT detectors. Collimated high-energy x-rays, produced by a superconducting wiggler at the National Synchrotron Light Source’s X17B1 beamline, allow for a nondestructive characterization of thick CZT samples (2–3 mm). In order to have complete information about the defect distribution and strains in the crystals, two series of experiments have been performed. First, a monochromatic 67 keV x-ray beam with the size of 300×3…
An XRD, TEM and Raman study of experimentally annealed natural monazite
2002
The healing of radiation damage in natural monazite has been experimentally studied in annealing experiments using XRD, TEM, Raman microprobe and cathodoluminescence analysis. The starting material was a chemically homogeneous monazite from a Brazilian pegmatite with a concordant U–Pb age of 474 ± 1 Ma and a U–Th/He age of 479 Ma. The monazite shows nm-scale defects induced by radioactive decay. The Xray pattern of the unheated starting material revealed two distinct monazite ''phases'' A and B with slightly different lattice parameters. Monazite A shows sharp reflections of high amplitudes and slightly expanded lattice parameters (1% in volume) compared to a standard monazite. Phase B exhi…
Structural investigation of four-centre photopolymerisation of bis-phthalamic bis-chalcone derivative in the crystalline state
1997
By combining the results obtained from an electron diffraction tilting series with solid state NMR and powder X-ray diffraction, it was possible to determine the unit cell parameters and space group of BPABC crystals grown from DMAA solution both before and after irradiation. Subsequently semi-empirical quantum mechanical and packing energy calculations led to a model structure which agreed well with all the electron diffraction data and thus provided insight into the cross-linking mechanism. © 1997 John Wiley & Sons Ltd.
Simultaneous IR and time-resolved X-ray diffraction measurements for studying self-sustained reactions.
1998
Self-propagating high-temperature synthesis provides an attractive practical method for producing advanced materials such as ceramics, composites and intermetallics. This kind of reaction has been investigated in situ using time-resolved X-ray diffraction, with an X-ray synchrotron beam (D43 beamline, LURE, Orsay) coupled to simultaneous IR thermography to study structural transformations and thermal evolution. With short acquisition times (30 ms per pattern) it has been possible to observe several steps before obtaining compounds. Two different compound formations have been described: (i) the different steps of reaction, aluminium melting, subsequent temperature increase and fast reaction …
Time-resolved X-ray powder diffraction on a three-way catalyst at the GILDA beamline
2003
Time-resolved X-ray diffraction experiments carried out at the beamline BM08-GILDA of ESRF allowed a study of the structural modifications taking place in a Pt/ceria-zirconia catalyst while the CO oxidation reaction was in progress. The capillary tube in which the sample is stored acts effectively as a chemical microreactor that ensures homogeneity of the sample treatments and minimization of diffusion effects. During the flowing of the reactant CO/He mixture, the investigated catalyst undergoes a fast Ce(IV)-Ce(III) partial reduction that involves the release of one O atom for every two reduced Ce cations. Because Ce(III) has a larger ionic radius than Ce(IV), the structural modification p…
Effect of gamma radiation on thermostimulated exoelectron emission from Gd2O3 films
2020
Abstract The effect of gamma irradiation on Gd2O3 films was studied using the thermostimulated exoelectron emission (TSEE) technique. The films were deposited on a glass and Si/SiO2 substrates using an extraction-pyrolytic method. Crystalline structure, chemical composition, film thickness and surface morphology were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films were irradiated by 10 MeV gamma photons and TSEE was measured from the irradiated films. It was found that gamma irradiation decreases TSEE intensity and the area below TSEE spectral curves. A linear correlati…
Levels of 188Re nucleus populated in thermal neutron capture reaction
2016
Abstract Levels of 188 Re populated in thermal neutron capture reaction with enriched 187 Re targets have been studied. Single γ -ray spectrum of 188 Re, measured with the high-resolution crystal diffraction spectrometer GAMS5, as well as γγ -coincidence experiments performed with high efficiency Ge detectors, allowed to develop model-independent level scheme of the doubly-odd 188 Re nucleus up to ∼ 1.5 MeV excitation energy. Analysis of the established 188 Re level scheme in terms of the quasiparticle-plus-rotor model indicates coexistence of axially-deformed and triaxial structures in the energy range above 400 keV.
Pressure-induced phase transformations in mineral chalcocite, Cu2S, under hydrostatic conditions
2014
Abstract High-pressure room-temperature angle-dispersive powder X-ray diffraction measurements on Cu2S chalcocite were performed up to 30 GPa using a diamond-anvil cell, He as pressure transmitting medium and synchrotron radiation. Two first-order phase transitions were found at 3.2 and 7.4 GPa. The indexation of the powder diffraction patterns suggests three different monoclinic cells for the low-pressure chalcocite and the two high-pressure phases. Subtle changes in the X-ray diffraction patterns suggest a third pressure-induced transition above 26 GPa. Structural parameters and compressibility are discussed and compared to those reported in a previous study on Cu2S nanowires.