Crystal Structures of New Chalcogenide- Containing Yttrium Orthosilicates Y<Subscript>2</Subscript>SiO<Subscript>4</Subscript>Q (Q = S,Se)

Compounds Y₂SiO₄Q (Q = S, Se) are obtained by the interaction of oxides and elemental substances in cesium chloride flux. The structures of these compounds are determined by the single crystal XRD analysis. These compounds isostructural and crystallize in the space group Pbcm with the following parameters: Y₂SiO₄S (I) a = 6.0462(8) Å, b = 6.8976(9) Å, c = 10.6558(13) Å, V = 444.39(10) ų; Y₂SiO₄Se (II) a = 5.9935(7) Å, b = 6.9216(8) Å, c = 10.7688(12) Å, V = 446.74(9) ų. The measured fluxing points are 1650±15 °С for I and 1850±15 °С for II.     

Measurement of the $$\boldsymbol{\Sigma^{0}/\Lambda^{0}}$$ Yield Ratio in $${pA}$$ Interactions at 70 GeV

Physics of Atomic Nuclei - The active target with C, Si and Pb plates was irradiated in 70-GeV proton beam at U-70 accelerator. The signal (270 events) from $$\Sigma^{0}\to\Lambda^{0}+\gamma$$...     

Parametric x-ray radiation from 500-MeV electrons in a tungsten single crystal with a surface mosaicity less than 1.5′

The yield of parametric x-ray radiation from a tungsten single crystal irradiated with a E=500 MeV electron beam from the Tomsk Sirius synchrotron was studied experimentally in Bragg geometry. The tungsten sample was 1.7 mm thick and had a surface mosaicity less than 1.5′; it was oriented in such a way that the (111) face was at the Bragg angle of θ _B=45° with respect to the electron-beam direction. The x-ray photons were detected at the angle of 2θ _B=90° with respect to the electron beam. The angular distributions of parametric x rays are compared with those calculatedwith allowance for actual experimental conditions.     

Finite element simulation of nanostructuring burnishing

Dynamics simulation of burnishing of a thin steel layer beneath an indenter applied with a constant force and then moving with a constant velocity was performed by the finite element method in the plane strain approximation. The indenter was modeled by a perfectly rigid body, and the steel was modeled by an elastoplastic body with isotropic hardening according to an experimentally defined law. The regularities of changes in the stressstrain state of the material near the treated surface were studied and mechanisms of the formation of a nanostructured layer were disclosed. The effect of the friction coefficient and the burnishing force on the height of a bulge of edged material was analyzed. The results of studies agree well with experimental data.     

Parametric X Rays in the Region of Anomalous Dispersion

The influence of anomalous dispersion on the intensity of parametric x rays (PXR) is experimentally investigated in the present work. An experiment conducted with an inner electron beam generated by the Tomsk synchrotron with energy E ₀ = 900 MeV is discussed. A Ge monocrystal 0.17 mm thick oriented so that Bragg's angle _B between the electron momentum direction and the (111) plane is 9°30 is used as a target. The experimental data are compared with the results of calculations in the context of the kinematic PXR theory.     

Paramagnetic Mn Antisite Defects in Nanoceramics of Aluminum–Magnesium Spinel

Physics of the Solid State - The effect of structure and size parameters on the formation of intrinsic and impurity paramagnetic centers in nanoceramics of aluminum–magnesium spinel is...     

Soft Component of Emission from Channeled Electrons in a Silicon Crystal

The Tomsk synchrotron has been used to measure the emission spectrum and orientation dependences of the yield of photons with energies much smaller than the emission energy of channeled electrons. The measurements have been performed with a crystal-diffraction spectrometer. For electrons incident along the (110) axis, the radiation intensity in the energy range 30 360 keV exceeds the bremsstrahlung one by almost an order of magnitude. The shape of the emission spectrum does not coincide with that of the bremsstrahlung spectrum. The radiation intensity increases smoothly with the photon energy. The bremsstrahlung spectrum from a disoriented crystalline target is satisfactorily described by the existing theory with phenomenological consideration of the polarization of the medium.