On the Generation of Intense Cs K X-Rays upon Electron Excitation of a Mo Target Heat Treated in Cs and O2 Vapors

JETP Letters - The possibility of stable generation of intense characteristic Cs radiation upon electronic excitation of a Mo anode target heat treated in Cs and O2 vapors is demonstrated. The...     

Energy-Dispersive Scheme with a Bandpass Filter for Determining Heavy Element Content from X-Ray Absorption Spectra

An energy-dispersive scheme using a bandpass filter based on pyrolytic graphite is proposed for determining the content of heavy elements from X-ray absorption spectra. The detected excitation spectrum is corrected to increase the accuracy of measurement. The initial shape of the photoabsorption jump is reconstructed in the approximation of an isolated atom by numerically solving the convolution equation.     

Status of the High-Voltage Electron-Cooling System of the NICA Collider

Physics of Particles and Nuclei Letters - In order to achieve the design luminosity in the NICA collider, it is planned to equip it with both stochastic and electron cooling. The electron-cooling...     

Correlation between thermodynamic and kinetic fragilities in nonpolymeric glass-forming liquids

A phenomenological relationship between reduced excess heat capacity of supercooled liquid DeltaC(p)(exc)(T(g))DeltaS(m) at the glass transition temperature T(g), fragility index m, and reduced glass transition temperature T(rg)=T(g)T(m), where T(m) is the melting (liquidus) temperature, was derived for fragile nonpolymeric glass-forming liquids under the assumptions that the fragile behavior of these liquids is described by the Vogel-Fulcher-Tammann (VFT) equation; the excess heat capacity of liquid is inversely proportional to the absolute temperature and the VFT temperature T(0) is equal to the Kauzmann temperature T(K). It was found that DeltaC(p)(exc)(T(g))DeltaS(m) is a composite function of m and T(rg), which indicates that the empirical correlation DeltaC(p)(exc)(T(g))DeltaS(m)=0.025m recently identified by Wang et al. [J. Chem Phys. 125, 074505 (2006)] is probably valid only for liquids which have nearly the same values of T(rg).     

Band reject filtration of the excitation spectrum at energy dispersive X-ray spectroscopy of weak signals

The possibility of the efficient band reject filtration of the continuous X-ray excitation spectrum in the energy range E ≥ 8 keV is demonstrated. This makes it possible to strongly increase the sensitivity of energy dispersive X-ray spectroscopy at detecting of weak fluorescence lines. Spectral rejection is implemented by transmitting a primary beam through highly oriented pyrolytic graphite with given structural parameters. Diffraction extinction in pyrolytic graphite ensures the possibility of reducing the intensity by more than 20 dB and rejecting the spectral band with a width of ~1 keV. The reduction of statistical fluctuations of the background of elastically scattered radiation is achieved when the bottom of the formed spectral valley is adjusted to the analyzed fluorescence line. The proposed scheme of band reject filtration also allows the suppression of intense characteristic lines in the primary and scattered radiation spectra.     

The energy dispersive scheme of X‐ray fluorescence analysis with a crystal polarizer and polycapillary optics

The efficiency of the polarization scheme based on polycapillary optics and a diamond crystal polarizer was demonstrated. The scheme provides suppression of the background of scattered radiation in measuring X‐ray fluorescence spectra. A quasi‐parallel X‐ray beam with an angular divergence of 4.2 mrad was formed by a microfocus source with a copper anode and polycapillary half‐lens. Simultaneous polarization and monochromatization of radiation was obtained with a crystal of natural diamond, which was set at the diffraction reflection (113). The degree of polarization of CuK_α1 spectral line and the maximum radiation flux were respectively equal to 99.86% and 5 · 10⁶ photon/s. In the direction orthogonal to the plane of diffraction, the maximum attenuation of the background was up to 19 dB.     

Asymmetry of quadrupole doublet of Mössbauer spectra in LiNbO3∶Fe

Polycrystalline samples of LiNbO₃ doped by the enriched⁵⁷Fe isotope have been studied at room and liquid nitrogen temperatures by nuclear γ-resonance (NGR). Iron impurity concentrations were 0.07, 0.30, 1.02, 2.06 at.%, the Li/Nb ratio being 0.935, 0.990, 1.000. An asymmetry of the quadrupole doublet of NGR experimental spectra has been found. Acceptable hypotheses are discussed to explain the nature of the asymmetry: the Goldanskii-Karyagin effect, the effect of sample texture, and the electron and nuclear spin-lattice relaxation effect. On the basis of computed NGR spectra and thorough analysis of the models we can conclude that there is tendency to form coupled pairs of Fe²⁺ cations in neighbour lithium and niobium sites. The probability of the formation of such pairs exceeds considerably the statistical value.     

Formation of Spectral Valleys in the Hard X-Ray Spectrum by Diffraction Band Reject Filtering

JETP Letters - The possibility of forming deep spectral valleys in the polychromatic spectrum of X rays with an energy of E ≥ 15 keV using diffraction band rejection is demonstrated....     

The influence of efficient atomic packing on the constitution of metallic glasses

Efficient atomic packing is shown to be a fundamental consideration in the formation of metallic glasses. A simple concept of packing efficiency, based on atom packing in the first coordination shell of solute-centred clusters, is proposed and developed. This model leads to the prediction that specific radius ratios, defined as the radius of the solute atom divided by the radius of the solvent atom, are preferred in the constitution of metallic glasses. Analysis of a large number of binary and complex metallic glasses shows that these specific critical radius ratios R* are indeed preferred in known metallic glasses. The predictions of this model extend previous proposals to describe the influence of topology on the formation of metallic glasses. Although this model represents a simple idealization, the strong agreement with published metallic glasses suggests that efficient atomic packing, enabled by solute-centred clusters, forms a fundamental consideration in the constitution of metallic glasses.