Showing papers in "Bulletin of The Russian Academy of Sciences: Physics in 2016"
TL;DR: In this article, the experimental cross sections of partial photoneutron reactions are evaluated for the 63,65Cu and 80Se isotopes, and the cross sections are free of systematic uncertainties from shortcomings of the experimental methods for neutron multiplicity sorting based on measurements of neutron energy used in experiments with quasimonoenergetic annihilation photon beams.
Abstract: The cross sections of partial photoneutron reactions are evaluated for the 63,65Cu and 80Se isotopes. The cross sections are free of systematic uncertainties from shortcomings of the experimental methods for neutron multiplicity sorting based on measurements of neutron energy used in experiments with quasimonoenergetic annihilation photon beams. An experimental-theoretical method is used to evaluate cross sections σeval(γ, in)= F
theor
σexp(γ, xn), where ratios F
theor
= σtheor(γ, in)/σtheor(γ, xn) = σtheor(γ, in)/σtheor[(γ, 1n) + 2(γ, 2n) + …] are calculated using a combined model of photonuclear reactions, and σexp(γ, xn) is the experimental cross section of the neutron yield reaction free from neutron multiplicity sorting problems. The cross sections are evaluated for reactions (γ, 1n) and (γ, 2n) for the 63,65Cu and 80Se isotopes, and for the total photoneutron reaction σ(γ, Sn) = σ[(γ, 1n) + (γ, 2n) + …]. It is shown that noticeable deviations of the experimental cross sections from the evaluated values result from the unreliable sorting of neutrons between the channels with multiplicities 1 and 2.
43 citations
TL;DR: In this article, a combined scheme of hot plasma confinement and laser and plasma-based methods for generating a megagauss field during the implosion of a magnetized target are described that allow the development of new high density plasma sources for materials science experiments and advanced areas of power engineering.
Abstract: A combined scheme of hot plasma confinement is proposed, and laser and plasma-based methods for generating a megagauss field during the implosion of a magnetized target are described that allow the development of new high-density plasma sources for materials science experiments and advanced areas of power engineering. A procedure for numerical calculation of the physical processes involved in the target plasma in an external magnetic field is presented.
18 citations
TL;DR: In this paper, the implantation formation of InAs nanoclusters in silicon and silica and their modification via irradiation with Xe ions with an energy of 167 MeV and a fluence of 3 × 1014 cm-2 are studied.
Abstract: The implantation formation of InAs nanoclusters in silicon and silica and their modification via irradiation with Xe ions with an energy of 167 MeV and a fluence of 3 × 1014 cm–2 are studied. It is found that post-implantation annealing and irradiation with high-energy ions alter the size and shape of nanoclusters and cause structural transformations within them. The ordering of nanoclusters and their elongation along the trajectory of Xe ions in a SiO2 matrix is observed.
11 citations
TL;DR: In this article, thin films of Pd-23% Ag composition are obtained by means of magnetron sputter deposition. The surfaces of the films are modified via the electrolythic deposition of finely divided palladium.
Abstract: Thin films of Pd–23% Ag composition are obtained by means of magnetron sputter deposition. The surfaces of the films are modified via the electrolythic deposition of finely divided palladium. The hydrogen permeabilities of samples of membranes (both smooth and modified with palladium black) are compared. A marked increase in the hydrogen permeability of the modified membrane is observed, compared to the smooth membrane. The dependence of the rate of hydrogen fluence on the excess pressure is approximated by a curve of the first order, demonstrating the limitations of the process of hydrogen permeation by hydrogen superficial dissociation.
11 citations
TL;DR: In this paper, the Schrodinger equation is numerically solved for the external neutrons of the 3He, 45Sc, and 197Au nuclei to calculate transfer probabilities and cross sections.
Abstract: Experimental cross sections for the formation of 196,198Au isotopes in the 3He + 197Au reaction and 44,46Sc isotopes in the 3He + 45Sc reaction are analyzed. To calculate transfer probabilities and cross sections, the time-dependent Schrodinger equation is numerically solved for the external neutrons of the 3He, 45Sc, and 197Au nuclei. It is shown that the contribution from the fusion channel with subsequent evaporation is important for the 3He + 45Sc reaction and negligibly small for the 3He + 197Au reaction. Fusion–evaporation is taken into account using the NRV and PACE codes. Calculation results demonstrate overall satisfactory agreement with experimental data.
10 citations
TL;DR: In this article, features of the generation of super radiance short pulses in a dielectric medium with quantum dots allowing for the nonlinear dissipative effects of the local field are considered.
Abstract: Features of the generation of super radiance short pulses in a dielectric medium with quantum dots allowing for the nonlinear dissipative effects of the local field are considered. It is shown that the problem can be reduced to an equation of a nonlinear pendulum with an additional term for the harmonic loss/gain.
10 citations
TL;DR: In this paper, the effect of glucose and glycerol on human and rat skin reflection spectra was studied in vivo by terahertz time-domain spectroscopy in the frequency range of 0.1-2.0 THz.
Abstract: Human and rat skin reflection spectra and the effect of glucose and glycerol on these spectra are studied in vivo by terahertz time-domain spectroscopy in the frequency range of 0.1–2.0 THz. Variations in skin optical properties proved to correlate with changes in the blood glucose level.
10 citations
TL;DR: The energy and the square modulus of the wave function for the ground states of helium nuclides 3,4,6He have been calculated by Feynman's continual integrals method as mentioned in this paper.
Abstract: The energy and the square modulus of the wave function for the ground states of helium nuclides 3,4,6He has been calculated by Feynman’s continual integrals method. A new parameterization of the shell model for light nuclei is proposed.
10 citations
TL;DR: In this paper, a modified hydrodynamic approach using a nonequilibrium equation of state is used to describe heavy-ion collisions at intermediate energies, and calculated energy spectra of protons produced in heavyion collisions are compared to experimental data and the results from calculations based on solving the Vlasov-Uehling-Uhlenbeck (VUU) kinetic equation.
Abstract: A modified hydrodynamic approach using a nonequilibrium equation of state is used to describe heavy-ion collisions at intermediate energies. The calculated energy spectra of protons produced in heavyion collisions are compared to experimental data and the results from calculations based on solving the Vlasov–Uehling–Uhlenbeck (VUU) kinetic equation.
9 citations
TL;DR: In this paper, the defect substructure of rail surface layers up to 10 mm thick during long-term operation (gross transit tonnages of 500 and 1000 mln t) was found via optical, scanning, and transmission electron microscopy.
Abstract: Patterns in the transformation of the structural and phase states and the defect substructure of rail surface layers up to 10 mm thick during long-term operation (gross transit tonnages of 500 and 1000 mln t) are found via optical, scanning, and transmission electron microscopy. According to the nature of the fracture and the degree of defectiveness, three layers can be distinguished: a surface layer, a transition layer, and the base metal. It is shown that the operation of steel rails is accompanied by full fractures in surface layers up to 15 μm thick with lamellar pearlite grains and the formation of ferrite–carbide mixtures with nanosized particles. The deformation of steel increases the densities of scalar and excess dislocations, the curvature–torsion values of the crystal lattice, and the amplitudes of internal stress fields. Structural elements that can act as stress concentrators are identified.
9 citations
TL;DR: In this paper, structural and morphological studies, measurements of the sheet electrical resistance, and estimating resistivity ρm of a graphite-like conducting surface layer formed upon high-dose irradiation of the (111) face of a synthetic diamond with Ar+ ions at an energy of 30 keV and a target temperature of 400°C are presented.
Abstract: Results from structural and morphological studies, measurements of the sheet electrical resistance, and estimating resistivity ρm of a graphite-like conducting surface layer formed upon high-dose irradiation of the (111) face of a synthetic diamond with Ar+ ions at an energy of 30 keV and a target temperature of 400°C are presented. It is found that the orienting effect of the diamond lattice is visible in the suppression of the formation of graphite crystallites with axis c perpendicular to the surface. The thickness of the modified layer is 40–50 nm, and its sheet resistance is 0.5 kΩ/sq. Resistivity ρm = 20–25 μΩ m of the modified layer lies within the range of ρ values of graphite and glassy carbon materials.
TL;DR: In this paper, the specific surface energy of small nanoclusters of transition fcc metals is calculated using the many-particle tight-binding potential and its earlier analog, the Gupta potential.
Abstract: The specific surface energy of small nanoclusters of transition fcc metals is calculated using the many-particle tight-binding potential and its earlier analog, the Gupta potential. The calculations are performed using both a theoretical model and computer simulations based on the Monte Carlo method. The equimolecular surface is considered as the dividing surface. It is found that at short radii of the nanoclusters, the surface energy and surface tension grow linearly as the particle radius increases. The values of the coefficient of proportionality in the dependence of the specific surface energy on the radius of a nanocluster are compared to the available literature data, experimental and otherwise.
TL;DR: In this article, a Clifford extension of the Grassmann algebra is considered in which operators are built from products of Grassmann variables and derivatives with respect to them, and it is shown that a subalgebra of operators, isomorphic to the usual matrix algebra, can be separated in this algebra, while the algebra itself is a generalization of the matrix algebra and produces transformations of supersymmetry.
Abstract: A Clifford extension of the Grassmann algebra is considered in which operators are built from products of Grassmann variables and derivatives with respect to them. It is shown that a subalgebra of operators, isomorphic to the usual matrix algebra, can be separated in this algebra, while the algebra itself is a generalization of the matrix algebra, contains superalgebraic operators expanding the matrix algebra, and produces transformations of supersymmetry.
TL;DR: In this paper, known experimental and model-calculated data, along with independent calculations using the TALYS-and EMPIRE-codes, are compiled for the cross sections of reactions 14N(γ, 2n)12N, 14N (γ, p)12B, and 13C(γ and p) 12B used in the photonuclear technique under development for the detection of hidden explosives.
Abstract: Known experimental and model-calculated data, along with independent calculations using the TALYS- and EMPIRE-codes, are compiled for the cross sections of reactions 14N(γ, 2n)12N, 14N(γ, 2p)12B, and 13C(γ, p)12B used in the photonuclear technique under development for the detection of hidden explosives. Indications of a substantial underestimate of model-calculated values, compared to the available measured results, are obtained.
TL;DR: In this article, the motion of spherical microparticles with sizes less than or comparable to the wavelength of ultrasound (300 μm) in a gel-like medium is studied, and it is shown that a specific feature of microparticle motion is their complete deceleration for a time of about 1 ms after switching off the ultrasound, and their subsequent displacement is determined entirely by the medium's relaxation.
Abstract: The motion of spherical microparticles with sizes (50–250 μm) less than or comparable to the wavelength of ultrasound (300 μm) in a gel-like medium is studied. Particle displacement is defined by the acoustic radiation force and the motion of the medium. It is shown that a specific feature of microparticle motion is their complete deceleration for a time of about 1 ms after switching off the ultrasound, and their subsequent displacement is determined entirely by the medium’s relaxation. The aim of the work is to develop ultrasonic means of detecting microcalcifications in breast tissues.
TL;DR: In this paper, a mathematical model of thermomechanical processes in the output window of a high-power continuous gas laser is developed and used to examine the windows of a СО2 laser.
Abstract: A mathematical model of thermomechanical processes in the output window of a high-power continuous gas laser is developed and used to examine the windows of a СО2 laser. The dependence of the maximum allowed output radiation power on the beam diameter and the distributions of temperatures and mechanical stresses are obtained, and the divergence of radiation is studied for windows made from ZnSe, KCl, and polycrystalline diamond (PD). In addition, the damage threshold of a composite output window made from PD with a single-crystalline region at the center is considered.
TL;DR: In this article, the potential of the 4He-9Be interaction with light 9Be nuclei was studied under the double folding model using the wave function of the ground state of the 9Be nucleus constructed in the three-cluster α + α + n approximation, and differential cross sections of elastic and inelastic 4He−9Be scattering and single-nucleon transfer in the intermediate range of energies were calculated.
Abstract: Specific features of 4He interaction with light 9Be nuclei are studied. The potential of 4He–9Be interaction is calculated within the framework of the double folding model using the wave function of the ground state of the 9Be nucleus constructed in the three-cluster α + α + n approximation. The differential cross sections of elastic and inelastic 4He–9Be scattering and single-nucleon transfer in the intermediate range of energies are calculated. Comparative analysis of experimental and calculated results demonstrate their good agreement, indicating that the model assumptions on the cluster structure of 9Be nucleus are valid.
TL;DR: In this article, the laser synthesis of nanoparticles/nanoclusters with different topologies in semiconductor PbTe samples is performed via direct laser modification of thin films under the action of continuous laser radiation with a wavelength of 1.06 μm and a power density of ~105 W/cm2.
Abstract: Methods of laser modification allow us to observe macroscopic quantum phenomena in nanostructured (cluster) materials. The laser synthesis of nanoparticles/nanoclusters with different topologies in semiconductor PbTe samples is performed via direct laser modification of thin films under the action of continuous laser radiation with a wavelength of 1.06 μm and a power density of ~105 W/cm2. Nanoparticles with bimodal distribution in lateral dimensions are obtained on the surfaces of the samples. The electrophysical properties of such structures can be controlled as desired by modifying their topology. Variations in electric properties depending on the particle location density are demonstrated. The results are interpreted based on the existence of quantum coherent processes with tunneling transitions and hopping conductivity. This approach is promising for the fabrication of elements and devices in optoelectronics and photonics based on new physical principles, and of different hybrid optoelectrical schemes.
TL;DR: In this article, a THz transistor based on a metamorphic nanoheterostructure with generation frequency fmax = 0.63 THz and a zigzag-shaped gate Lg = 46 nm long is developed.
Abstract: A THz transistor based on a metamorphic nanoheterostructure with generation frequency fmax = 0.63 THz and a zigzag-shaped gate Lg = 46 nm long is developed. A series of low-temperature GaAs structures are produced, and photoconductive antennas with generation frequencies above 1.5–2 THz are developed on their basis.
TL;DR: In this paper, different modes of conjugate heat transfer in a crystal environment with geometry similar to the upper part of a Czochralski thermal unit are investigated numerically, and the thermal stress fields in the crystal are calculated using the resulting temperature fields.
Abstract: Different modes of conjugate heat transfer in a crystal environment–growth chamber walls system with geometry similar to the upper part of a Czochralski thermal unit are investigated numerically. Calculations are performed for an argon Prandtl number of 0.68 and a Grashof number of 16000. The thermal stress fields in the crystal are calculated using the resulting temperature fields.
TL;DR: In this article, a new target system that includes on-line monitoring of target heating is used to determine the parameters of proton beams, experimental studies on nuclear reactions are performed using Ti, Cu and stainless steel targets.
Abstract: Nuclear reactions using proton beams and tin targets are studied in order to obtain antimony radionuclides. A new target system that includes on-line monitoring of target heating is used. To determine the parameters of proton beams, experimental studies on nuclear reactions are performed using Ti, Cu and stainless steel targets. Using modern model approximations, cross sections are determined for the formation of radionuclides 119Sb and 117Sb in the investigated nuclear reactions.
TL;DR: In this paper, the emission of γ-quanta, electrons, and positrons upon the decay of 12N and 12B produced in characteristic targets is calculated within radiation-matter interaction models generated using the GEANT and MCNP simulation software.
Abstract: The emission of γ-quanta, electrons, and positrons upon the decay of 12N and 12B produced in characteristic targets is calculated within radiation–matter interaction models generated using the GEANT and MCNP simulation software.
TL;DR: The atomic structure of GaSb/GaP quantum dots grown via molecular beam epitaxy on a (100) GaP surface at epitaxy temperatures of 420-470°C was investigated in this paper.
Abstract: The atomic structure of GaSb/GaP quantum dots grown via molecular beam epitaxy on a (100) GaP surface at epitaxy temperatures of 420–470°C is investigated. It is established that, depending on morphology of the GaP growth surface, the deposition of 1 ML of GaSb leads to the formation of strained Ga(Sb, P)/GaP or fully relaxed GaSb/GaP quantum dots. The obtained heterostructures exhibit high photoluminescence efficiency.
TL;DR: In this paper, the problem of heat distribution in materials irradiated with finely focused medium-energy electron beams is considered by means of mathematical simulation, and a model is developed by solving a multidimensional heat-transfer steady equation using the Green function.
Abstract: The problem of heat distribution in materials irradiated with finely focused medium-energy electron beams is considered by means of mathematical simulation. A model is developed by solving a multidimensional heat-transfer steady equation using the Green function. A model that can be applied to a broad class of solid bodies and the range of energies of primary electrons is used as the source function. Some results are illustrated using the example of semiconductor materials used in electronics.
TL;DR: In this paper, the effectiveness of nonthermal action produced by nanosecond high voltage pulses for targeted changes in the phase (functional chemical) composition and technological properties of rock-forming minerals of kimberlites and diamonds is shown.
Abstract: Using a set of physicochemical methods (XPS, analytical electron microscopy, the adsorption of acid–base indicators, and measuring microhardness), the effectiveness of nonthermal action produced by nanosecond high voltage pulses for targeted changes in the phase (functional chemical) composition and technological properties of rock-forming minerals of kimberlites and diamonds is shown. According to data obtained via XPS and SEM-EDX analyses, pulse energy actions damage the surface microstructure of dielectric minerals with the subsequent formation of traces of surface breakdowns and microcracks, softening rockforming minerals, and reducing their microhardness by 40–66% overall. The following changes in the functional chemical composition of a geomaterial surface are established through the adsorption of acid–base indicators: mutual transformations of the Bronsted base, Lewis base, and Bronsted acid sites on a calcite surface under the action of an electromagnetic pulse and the hydroxylation and/or formation of carbonyl groups on a diamond surface, doubling the diamond electrokinetic potential in the negative range.
TL;DR: In this paper, the effect of megaplastic deformation on the coercivity and specific saturation magnetization of soft-magnetic equiatomic FeNi alloy is studied at room temperature in a Bridgman chamber by means of X-ray diffraction, Mossbauer spectroscopy and magnetometry.
Abstract: The effect megaplastic deformation has on the coercivity and specific saturation magnetization of soft-magnetic equiatomic FeNi alloy is studied at room temperature in a Bridgman chamber by means of X-ray diffraction, Mossbauer spectroscopy and magnetometry. Structural features responsible for changes in the alloy’s properties at different stages of deformation are revealed.
TL;DR: In this article, a theoretical model based on long-range dispersion corrections of the charge density functional is proposed for model Hg2Cl2 calomel crystals, typical representatives of molecular inorganic compounds where the intermolecular interaction is found to play an important role.
Abstract: A theoretical model based on long-range dispersion corrections of the charge density functional is proposed for model Hg2Cl2 calomel crystals, typical representatives of molecular inorganic compounds where the intermolecular interaction is found to play an important role. This model successfully describes the electronic state and the phonon spectrum of the above crystal, predicts the earlier unstudied phase transition at high hydrostatic pressure. Study of the baric behavior of the phonon spectrum with Raman spectroscopy observes the soft mode in the low-symmetry orthorhombic phase with the frequency softening as the pressure rises. Pressures above 9 GPa considerably transform the Raman spectra, indicating a structural phase transition.
TL;DR: In this article, a dynamic model was used to describe the last stage of nuclear fission, the postscission motion of fission fragments, and it was shown that the dissipated energy can be as high as 10% of the average experimental kinetic energy.
Abstract: A dynamic model developed earlier is used to describe the last stage of nuclear fission: the postscission motion of fission fragments. In this process, Coulomb repulsive energy turns into the kinetic energy of fission fragments measured by experimenters. It is shown that the dissipated energy can be as high as 10% of the average experimental kinetic energy.
TL;DR: In this article, the existence of chain paramagnetic Curie-type contributions to the temperature dependence of static magnetic susceptibility χ(T) in the normal (nonsuperconducting) state is obtained for a series of pure YBa2Cu3O6 + δ high temperature superconductors with different oxygen contents (0.6 < δ ≤ 1).
Abstract: Experimental evidence for the existence of chain paramagnetic Curie-type contributions to the temperature dependence of static magnetic susceptibility χ(T) in the normal (nonsuperconducting) state is obtained for a series of pure YBa2Cu3O6 + δ high temperature superconductors with different oxygen contents (0.6 < δ ≤ 1). It is shown that the chain contribution is obvious on χ(T) curves only in the T < 150K range of temperatures, grows along with the number of oxygen vacancies in Cu1–O4 chains, and depends on the ordering of these vacancies.
TL;DR: In this article, the effect applied voltage frequency has on bipolar resistive switching in microcontact type heterostructures based on thin films and single crystals of bismuth selenide is studied both experimentally and via numerical simulation.
Abstract: The effect applied voltage frequency has on bipolar resistive switching in microcontact type heterostructures based on thin films and single crystals of bismuth selenide is studied both experimentally and via numerical simulation.