DOUBLE REFRACTION AND REFLECTION OF SURFACE SPIN WAVES IN BIAXIAL FERROMAGNETIC INSULATORS

Yu.I. Gorobets, S.O. Reshetnyak

Full Text :   (2500 kB, Ukr.) 

Abstract
The processes are considered of refraction and reflection of surface spin waves in inhomogeneous dielectric ferromagnetic medium. In the frameworks of the formalism of spin density in exchange mode the equation of magnetic moment dynamics and the dispersion low of spin waves are obtained. The eikonal equation and refraction indexes are obtained. The field and frequency dependencies of refraction indexes and reflection coefficients of spin waves are defined in an interface of two uniform biaxial ferromagnets with different parameters of exchange interaction, magnetic anisotropy and saturation magnetization. It is shown the possibility to use the proposed system as spinwave analogs of optical devises.

KEY WORDS: magnetic field, spin waves, refraction, anisotropy, reflection.

NUMERICAL CALCULUS OF PROPAGATION FEATURES OF NEUTRON-TEMPERATURE OSCILLATIONS IN CONTROLLED NUCLEAR SYSTEMS

V.A. Rudakov, A.A. Vodyanitskii

Full Text :   (700 kB, Rus.) 

Abstract
The developed theoretical model and experimental measurements on reactors VVER-1000 of the Zaporozhye NPP neutron of noise depending on frequency testify about intensive density oscillations of thermal neutrons in neutron multiplying systems with the coolant. Amplitudes of signals considerably decrease with frequency growth. At its small values (from shares of unit to several tens in Hz) amplitudes of fluctuations are subject to the strengthening, the obliged convective carrying over of neutrons by the coolant. The numerical analysis of the dispersive equation in the conditions of various types connections of oscillations is carried out. The numerical analysis verifies analytical results about a dispersion and strengthening (recession) of eigen neutron and temperature waves in approach of their weak interaction. Obtained data on conditions of propagation of strongly connected neutron and temperature fluctuations reflect nuclear- physical kinetic of neutron multiplying system together with a coolant hydrodynamics.

KEY WORDS: neutron-temperature fluctuations, numerical calculations, neutron multiplying systems, factor of spatial strengthening.

A SIMPLE MODEL OF NEUTRON TRANSPORT AND ITS APPLICATION FOR THE CALCULATION OF THE RESPONSE FUNCTIONS FOR THE BALL NEUTRON SPECTROMETER

A.Yu. Buki, S.A. Kalenik

Full Text :   (2500 kB, Rus.) 

Abstract
A simple model that provides a simulation of neutrons transportation in various materials in the energy range from 10^-8 to a few MeV had been developed. The model is implemented in code C++. In performing the test calculations the model showed a significantly higher speed than using a package GEANT 4. With the help of the model the response function of a spherical neutron spectrometer had been calculated.

KEY WORDS: simulation, neutrons, neutron fields, neutron spectrometer, response functions.

FORMING FEATURES OF THERMOELASTIC PEAKS AT HEAVY METAL BOMBARDMENT BY IONS OF LOW AND INTERMEDIATE ENERGIES

A.I. Kalinichenko, S.S. Perepelkin, V.E. Strelnitskij

Full Text :   (1100 kB, Rus.) 

Abstract
Possibility of forming of the subsurface nonlocal thermoelastic peaks (SNTP) by ions of low and intermediate energies E≤1 MeV in heavy metals is investigated. By examples of ions Xe⁺(U⁺) implanted to amorphous or (nano)crystalline Au(U), the existence of such ion boundary energy ~ (15-50) keV is shown that the SNTP with energy forms according to the model of NTP of low-energy ion which was earlier proposed. By the judgement method of cascades appearing at computer simulation of ion bombardment process the values E_NTP are determined for examined combinations of "ion-metal". It is shown that SNTP formation is possible at E > E_NTP as a simply heating region appearing on basis of subsurface (sub)cascade. SNTP parameters are determined by (sub)cascade size, heat smearing and phonon loss in the (sub)cascade. Upper estimate of probability of spherical SNTP formation with material melting for combinations "U⁺ - U","Xe⁺ - Au" and ion energy is given.

KEY WORDS: low-energy ion, amorphous and/or (nano)crystalline target, heavy metals, atomic cascade, thermoelastic peak, melting.

SPECTRAL CHARACTERISTICS RESTORATION OF X-RAY ELECTRONS RADIATION IN CRYSTALS BY MEANS OF RELATIVE CXR YIELDS FROM SECONDARY TARGETS

O.S. Deiev

Full Text :   (1800 kB, Rus.) 

Abstract
In the GEANT 4.9.2 the interaction of the primary X-rays electromagnetic radiation with the secondary converter atoms was calculated, K-lines yields of characteristic X-rays radiation (CXR) were computed. Spectra of the primary radiation N_RENT(E) = f (E) was simulated, analogous to the shape of the bremsstrahlung of electrons in crystals. X-rays were sent to the secondary target and excited the CXR, which was registered by the detector at angels 90°-180°. The ratio X_RENT(E) yield of intense X-ray bremsstrahlung radiation from oriented crystal to the yield of a disoriented crystal was determined (axis/random). The ratio (axis/random) of yields X_CXR(E) from secondary targets in the energy range 7-115 keV were calculated. The energy dependence X_RENT(E) и X_CXR(E) were compared. Shown that recovery of low-energy bremsstrahlung spectra of channeled electrons is possible when the radiation spectrum of channeled electrons has a monotonous dependence with no complex structure.

KEY WORDS: converters, secondary radiations, CXR, restoration of spectra, modeling, GEANT 4.9.2

MEASUREMENT METHODIC OF THE CROSS-SECTIONS, ANGULAR AND MASS DISTRIBUTIONS OF THE DEBRIS AT ELECTROFISSION OF HEAVY NUCLEI IN THE REGION OF GIANT RESONANCE

V.I. Kasilov

Full Text :   (2500 kB, Rus.) 

Abstract
A methodic is proposed to obtain cross-sections of electrofission of heavy nuclei in the energy region of giant resonance using the experimental measurements of the ratio of the photofission yield to the electrofission cross-section. Fission fragments are registered using glass cover and mailar films which are insensitive to charged background accompanying the fragments. A method has been proposed for cleaning the electron beam from gamma-background as well as the method of angular and mass distribution measurement of fission fragments.

KEY WORDS: electron beam, nuclear fission, fission chamber, electro-and photofission of nuclei, the deflecting magnet, the detector of fission fragments.

EXPERIMENTAL INVESTIGATION OF COMBUSTION MODES AND CONTRACTION OF GLOW DISCHARGE IN CF₄

V.A. Lisovskiy, O.I. Pelustka, V.A. Koval

Full Text :   (2300 kB, Rus.) 

Abstract
This paper studies in experiment the diffuse and contracted modes of dc glow discharge in CF₄. The existence region for the contracted mode with pressure unchanged is found to be limited from the small inter-electrode gap side, this boundary being multi-valued. A contracted column establishes in a stratified positive column with current increasing and inter-electrode gap or gas pressure fixed. However with subsequent current increase the length of the positive column decreases (with simultaneous considerable expansion of the negative glow), and contraction vanishes. At longer inter-electrode gap the current increase does not lead to contraction vanishing.

KEY WORDS: DC glow discharge, contraction, diffuse mode of the discharge, dissociation, CF₄

DEFORMATION PARAMETERS EXCITED STATES OF THE NILSSON MODEL

N.A. Shlyahov

Full Text :   (2100 kB, Rus.) 

Abstract
The review of the major models used for the description of the spectroscopic characteristics of the deformed nuclei is given. The difficulties conditioned by the uniqueness of the choice of nuclear deformation parameters in rotational bands are traced. The calculations of the reduced probabilities of electromagnetic transitions in the sd-shell odd nuclei performed within of the modified Nilsson model show that the use of different values of deformation parameters for different excited states gives better fits to the experimental data.

KEY WORDS: models of the deformed nuclei, the modified Nilsson model, deformation parameters for different excited states, sd-shell nuclei.

THE STRUCTURAL CHANGES IN SURFACE LAYER OF MATRIX ALUMINUM ALLOYS 1201 AND 6111 IN AREA OF PULSED BEAM OF RELATIVISTIC ELECTRONS INFLUENCE IN PRE-MELTING REGIME

V.V. Bryukhovetsky, V.F. Klepikov, V.V. Lytvynenko, A.V. Poida, V.P. Poida, A.G. Ponomaryov, M.A. Pryhoda, E.M. Prokhorenko, V.T. Uvarov

Full Text :   (1200 kB, Rus.) 

Abstract
In this work the features of the relativistic pulsed beam of electrons influence on the processes of structure formation in surface layer of industrial aluminum alloys 1201 and 6111 in pre-melting regime are investigated. It is shown, that in selected pre-melting regime - till the macroscopic surface melting in beam influence zone - the local melting and the subsequent crystallization of separate volumes of surface layer microstructure of alloys occurs. It is supposed, that the appearance of similar areas of microstructure of aluminum alloys 1201 and 6111 can be associated as with the nonequilibrium eutectics melting as with the melting of the segregations of alloying elements.

KEY WORDS: pulsed beam, electrons, aluminum alloys, microstructure of surface layer.

INTRINSIC PINNING AND EXCESS CONDUCTIVITY OF MONODOMAIN YBa₂Cu₃O_7-δ SINGLE CRYSTALS

Z.F. Nazyrov, N.M. Zavgorodnya, R.V. Vovk, D.A. Lotnik

Full Text :   (390 kB, Ukr.) 

Abstract
In present work the influence of the disorientation angle between the direction of constant field up to 15 kOe and the ab-plane α ≡ ∠(H,ab) to the temperature dependence of the excess conductivity in the temperature interval of the transition to the superconducting state in untwinned YBa₂Cu₃O_7-δ single crystals with a small oxygen hypostoichiometry are investigated. Causes of low-temperature "tails" (parakogerentnyh transitions) in the resistive transitions in superconducting state are analyzed in the framework of the implementation of the various regimes of the phase state of vortex matter.

KEY WORDS: excess conductivity, YBa₂Cu₃O_7-δ single crystals, oxygen deficiency, pinning, 2D-3D crossover, intrinsic pinning.

AMPLITUDE AND COUNT RATE CHARACTERISTICS OF “HAMAMATSU PHOTONICS” MULTI PIXEL PHOTON COUNTERS S10931-050P AND S10931-100P

O.V. Dudnik, E.V. Kurbatov, E. Valtonen

Full Text :  

Abstract
Results of studies of output signal amplitude characteristics of "Hamamatsu Photonics K.K." silicon photomultipliers with pixel sizes 50×50 μm² and 100×100 μm² using various methods are presented. It is shown that the photon detection efficiency of the PM with larger pixel size increases more rapidly with increasing bias voltage due to better geometric efficiency. At the same time the range of overvoltage producing linear output signals for this PM is much narrower than for the PM with smaller pixel size. Recommendations on the choice of operational bias voltages for both silicon PMs are presented. Maximal count rates of the silicon PMs are measured at various light intensities with a laser diode as the source of optical photons.

KEY WORDS: photomultiplier, photon detection efficiency, single photoelectron mode, operational amplifier, silicon PM, count rate, oscilloscope, scintillation detector.

DISTRIBUTION AND GROWTH FACTORS OF POLYCRYSTALLINE GRAINS IN 2D AND 3D STRUCTURES

V.G. Kirichenko, O.V. Kovalenko, V.N. Leonov

Full Text :   (2500 kB, Rus.) 

Abstract
In this work we study the influence of the alloys structure based on iron and zirconium, and two-dimensional structure of graphene on the orientation relations that characterize the grain size distribution. Method for determination of grain size and orientation relationships between the prepared projections of grains according to the optical metallography using a control sample of alpha-iron and steel Cr18Ni10Ti real thin section, zirconium alloy (3D-structure) and graphene (2D-structure) allowed the leads to the conclusion of a preferential allocation of grains such as polygons with Dirichlet sum of interior angles in the range 2π - 4π with a decrease in the amount up to (π - 2π) for graphene.

KEY WORDS: microstructure, polycrystal, grain, thermomechanical treatment, distribution, orientation.

INFLUENCE OF LASER IRRADIATION ON THE SURFACE STRUCTURE OF ZIRCONIUM ALLOYS

V.G. Kirichenko, O.V. Kovalenko, V.N. Leonov, S.V. Starostenko, T.А. Kovalenko, D.A. Kolesnikov

Full Text :   (1900 kB, Rus.) 

Abstract
The results of studying the effect of laser pulse (duration 50 ns) irradiation on the structure of the surface layers of zirconium alloys. As a result of laser irradiation of the zirconium alloys surface are formed amorphous phases, the concentration of inclusions of intermetallic phases in the surface layer depth of 0.3 microns is reduced by almost half. On the surface alloys formed by the wave structure due to the rapid solidification of the liquid melt, whose front is moving at high speed due to possible Kelvin-Helmholtz instability or the occurrence of crystallization waves at the surface irradiated spot.

KEY WORDS: radiation stability, Zirconium, alloys, surface, ion irradiation, amorphisation, crystallization.

STRUCTURE AND COAGULATION OF DISPERSE OXIDE INCLUSIONS IN THE ALPHA-IRON

V.G. Kirichenko, V.N. Leonov

Full Text :   (2200 kB, Rus.) 

Abstract
The results of studying the structure and phase composition of dispersed oxide inclusions of particles and coagulation of yttrium, aluminum, zirconium particles oxides, in a model system based on carbonyl iron. The observed oxide particles distributed in size over a wide range and elemental analysis of the cross section of yttrium oxide particles gives Y₂O_2,73. The resulting distribution of elements and the concentration gradient over the cross section of complex oxide possible to determine the nature of the agglomeration of particles in a metal matrix.

KEY WORDS: iron, nanoparticles, oxide, yttrium, structure, phase composition, coagulation .

INFLUENCE OF HEAT TREATMENT ON KINETICS OF SENESCENCE F THE NATURAL MICROCOMPOSITE OF Al-CuAl₂

V.E. Semenenko, A.A. Kasilov, Т.О. Kovalenko

Full Text :   (3100 kB, Rus.) 

Abstract
The influence of speed of cooling of aluminium-copper alloys on character of redistribution of alloying elements in a matrix solid solution is studied. The parameters of grate, microhardness of lamellar microcomposite are certain in a post-crystallizational period. Possible reasons of change of microstructures, conditioned tempering and discussed.

KEY WORDS: heat treatment, tempering, lamellar microcomposite, lattice parameter, microhardness.

AN EXPERIMENTAL STUDY OF AIR BUBBLES DYNAMICS IN WATER AT THE RAPID DECOMPRESSION

B.V. Borts, Y.G. Kazarinov, S.F. Skoromnaya, V.I. Tkachenko

Full Text :   (3800 kB, Rus.) 

Abstract
The processes of air bubbles emission in a tap water at the fast decompression are experimentally investigated. Experiments were carried out on the experimental setup - a high-pressure cell with a useful volume of 10.6 cm3. The cell can withstand pressures up to 20 MPa. Rapid decompression was achieved by tearing the aluminum foils due to the slow rise of pressure in the cell by the plunger. The tearing of foils began at a pressure, which was set by a certain number of foils. It is shown that volume of a single bubble compressed to 10 MPa after a rapid decompression at time t = 0.33 s sharply increases. Further at t > 0.5 s large bubbles slowly absorb the nearby small air bubbles. At large time scale (t >3 s) the process of release and redistribution of gas bubbles is completed. A qualitative agreement of theoretical calculations with obtained experimental results is shown.

KEY WORDS: decompression, tap water, gas saturation, high-pressure cell, the self-similar dynamics

INFLUENCE OF THE ELECTRONIC SPECTRUM FEATURES ON THE ELECTRON MOBILITY OF MO AND MО - RE ALLOY

T.A. Ignatyeva, A.N. Velikodnyy

Full Text :   (1500 kB, Rus.) 

Abstract
The of electrons mobilities adjusted for critical experimental results of the Mo and Mo-Re alloys Hall effect measurements were used for the calculation temperature dependence energy of the Mo electronic spectrum. It was shown that the temperature of 50K could be related to the mobility edge of localized electron states at the spectrum edge in narrow energy interval; from critical energies, when generation of the small electronic groups took place, to activation energy attributed to electron delocalization. In the case of Mo - there are ε_С1 energy of the generation of small electronic lens below Fermi level and ε_С2 energy above Fermi level, which accompanied by the formation of new electronic cavity of the Fermi surfaces under Rе doping. In summary, Fermi level movement, under external impact in relation to the critical energy of electron spectrum, led to electronic-topological transitions which simultaneously have the features of metal-dielectric transitions.

KEY WORDS: mobility electron, critical energies of the electronic spectrum, edge to mobilities, electronic- -topological transition, electron localization.