Small-Angle Neutron Scattering at the Pulsed Reactor IBR-2: Current Status and Prospects

Crystallography Reports - Neutron diffraction studies on the small-angle neutron spectrometer YuMO (Joint Institute for Nuclear Research, Dubna), based on the IBR-2 pulsed reactor, have been...     

Analysis of neutron spectra and fluxes obtained with cold and thermal moderators at IBR-2 reactor: Experimental and computer-modeling studies

The results of experimental and computer-modeling investigations of neutron spectra and fluxes obtained with cold and thermal moderators at the IBR-2 reactor (Joint Institute for Nuclear Research (JINR), Dubna) are presented. These studies are for the YuMO small-angle neutron scattering (SANS) spectrometer (IBR-2 beamline 4). The neutron spectra have been measured for two methane cold moderators for the standard configuration of the SANS instrument. The data from both moderators under different conditions of their operation are compared. The ratio of experimentally determined neutron fluxes of cold and thermal moderators is shown at different wavelengths. Monte Carlo simulations have been carried out to determine the spectra for cold-methane and thermal moderators. The results of calculations of the ratio of neutron fluxes of cold and thermal moderators at different wavelengths are demonstrated. In addition, the absorption of neutrons in the air gaps on the way from the moderator to the investigated sample is presented. SANS with the protein apoferritin was done with both cold methane and a thermal moderator and the data were compared. The prospects for the use of a cold moderator for a SANS spectrometer at IBR-2 are discussed. The advantages of using the YuMO spectrometer with a thermal moderator with respect to the tested cold moderator are shown.     

Refinement of estimates for some nonhomogeneous linear forms

In this paper, estimates for nonhomogeneous linear forms in values of hypergeometric functions with irrational parameters are refined. This refinement is carried out by means of an optimal choice of the degree of the zeroth polynomial appearing in the construction of approximate functional forms.Translated from Matematicheskie Zametki, vol. 77, no. 4, 2005, pp. 515–521.Original Russian Text Copyright © 2005 by P. L. Ivankov.This revised version was published online in April 2005 with a corrected issue number.     

Optical properties of Eu-doped zinc borate glasses

Photoluminescence, absorption and optical excitation spectra of undoped and Eu³⁺-doped binary zinc borate glasses of varied composition prepared by the melt quenching technique in air atmosphere were investigated. From photoluminescence measurements it was found that growing Eu³⁺ concentration leads to gradual disappearance of the broadband glass emission in the near-UV spectral range, while the red Eu³⁺ emission at 613 nm shows a considerable increase. This result together with excitation spectra suggests that the Eu³⁺ ions are excited via energy transfer from the initially excited glassy host. The glass composition strongly affects the position of the excitation maximum in the UV energy range.     

On values of hypergeometric functions with different irrational parameters

In this paper, we study the arithmetic nature of the values of generalized hypergeometric functions with different irrational parameters. Linear independence of such values is proved by means of an effective construction of the Pade approximation; corresponding quantitative results are obtained. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 6, pp. 65–72, 2005.     

On estimates of degrees of linear independence for some numbers

Translated from Matematicheskie Zametki, Vol. 55, No. 3, pp. 59–67, March, 1994.