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SIBERIAN JOURNAL OF PHYSICS. Scientific Journal. 2018. V13, i 4. |
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High-Energy and Accelerator Physics, Physics of High-Temperature Plasma
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Arzhannikov A. V., Bedenko S. V., Ivanov A. A., Modestov D. G., Prikhodko V. V., Sinitsky S. L.,
Shamanin I. V., Shmakov V. M., Titova A. M. Isotopic Composition Changes in the Fuel To study the neutron-physical characteristics of thorium-plutonium fuel, we have previously proposed to construct a facility consisting a subcritical assembly of a high-temperature nuclear reactor and a source of additional neutrons in the form of a plasma column. Additional neutrons are generated as a result of the D-D synthesis in this column of high-temperature plasma, which is created and confined in a long magnetic trap. The article presents the computer simulation results of the nuclear fuel evolution in the proposed facility. The simulation was carried out for plasma parameters, in which the D-D synthesis reaction gives the total neutron yield of 2E16 neutrons/s from the plasma column inside the subcritical assembly with a length of 3 m. Two variants of the fuel assembly operation mode, differing in the content of plutonium in the original thorium-plutonium fuel, are considered. In the first one, the initial plutonium fraction is 4 %, which ensures the subcritical state of the fuel assembly with an effective neutron multiplication factor kef = 0.95. In the second variant, the part of plutonium is increased up to 5 %, which allows the assembly to have kef = 0.99 at the operation conditions. The choice of such values of plutonium percentage was made according to the results of a detailed computer simulation of the main neutron-physical processes in the reactor core. The evolution of the fuel isotopic composition was calculated for the total time of the assembly operation – 3000 days. In the process of the fuel “burning” at the conditions of unchanged neutron yield from the plasma, a time decrease in the neutron multiplication factor and the power of the nuclear fission process in the reactor core from the beginning of the operating cycle was detected. To compensate this reduction in produced power, the required increase in the neutron yield from a plasma source is calculated. The article presents the simulation results and discusses various aspects of the solutions obtained.
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Physics of a Fluid, Neutral and Ionized Gases
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Popov V. N. Evaluation of Convective Mass Transfer during Pulsed Laser Heating of Steel Surface Numerical modeling of the processes during the alloying of the substrate surface metal layer under pulsed laser radiation is carried out. The proposed mathematical model is used to consider the various processes, such as: heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt. The surface of the substrate is covered with a layer of alloying substance that penetrates the melt. According to the results of numerical experiments, depending on the heating conditions of the substrate, two variants of the formation of the flow structure in the melt and the distribution of the alloying substance are determined.
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Shevchenko A. K., Yakovenko S. N. Simulation of Instability Development in a Plane Submerged Jet at Low Reynolds Numbers Numerical simulation of a plane submerged jet with Reynolds number of 32 < Re < 160 based on the mean inlet velocity and the flat slit height at the jet entrance is performed using the continuity and Navier – Stokes equations for incompressible fluid. The influence of changes in Re on the flow nature is studied with assignment of small random perturbations at the jet inlet and in the absence of these perturbations. In agreement with the available data of laboratory experiments, the present computation results show the laminar flow state in the first region near the exit from the slit, the asymmetric instability of sinusoidal type in the second, transitional region, and the irregular, turbulent nature of the flow in the third region. It is found that the lengths of the first and second sections decrease with increasing amplitude of small random perturbations introduced by distortion of the inlet velocity profile. Moreover, an increase in the Reynolds number leads to a shorter extension of the laminar section in agreement with the data of previous studies. Estimations are made for typical values of the wavelength of oscillations corresponding to the revealed effect of sinusoidal instability and for the typical frequency of these oscillations, which sharply increases with the growth of Re.
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Abdurakipov S. S., Dulin V. M., Tokarev M. P., Markovich D. M. Analysis of Coherent Structures in Circular and Chevron Jets The present study reports on measurements of the spatial shape and dynamics of large-scale coherent structures in circular and chevron submerged jets by the volumetric particle image velocimetry technique. A tomographic PIV system was used for the measurements of 3D velocity fields with 2 kHz acquisition rate. The datasets of PIV velocity fields were analyzed by spatial Fourier transform over the azimuthal angle and proper orthogonal decomposition (POD). It was concluded that for the chevron jet the turbulent kinetic energy of the axisymmetric mode m = 0, related with ring-like vortices in mixing layer of the jet, was more than twice smaller in comparison with the jet from a circular nozzle.
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Solid-State and Semiconductor Physics, Physics of Nanostructures
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Rodyakina E. E., Sitnikov S. V., Rogilo D. I., Latyshev A. V. Rearrangement of Atomic Steps on the Silicon (001) Surface at Sublimation under Heating by Direct Electric Current The combining atomic steps into bunches (groups of closely spaced steps) under conditions of electromigration, induced by direct current sample heating, on silicon surface (001) during sublimation in the temperature range 950- 1150°Ñ is studied using in situ reflection electron microscopy and ex situ atomic force microscopy. It is shown that changes in the average distance between the atomic steps bunches in time depend in a power-law manner, with an exponent of about 0.3. The data on the temperature dependence of the number of steps bunches per unit length, formed during the same time of annealing in the process of sublimation, has been obtained. It has been found that the temperature dependence is week with step-down current. The corresponding effective activation energy of the bunching process is about 0.24 eV with step-up current.
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Zolkin A. S., Semerikova A. I., Chepkasov S. Yu., Khomyakov M. N. Influence of the Carbon Ion Implantation on the Adhesion and Properties of Amorphous Carbon Films on Germanium A method for the synthesis of amorphous hydrogenated (a-C:H) carbon films with high adhesion is proposed, based
on the implantation of carbon ions into a monocrystalline germanium substrate. The flow of ionized carbon was created by an anode layer ion source in crossed electric and magnetic fields. Propane gas was introduced into the area
with an increased electron concentration. The gas flow rate was ranged from 4.5 to 10 cm3/min. Ionized fragments of
propane, including carbon, were accelerated by the electric field and deposited on the substrate. At the same time,
ionized carbon penetrated into the surface layer of germanium, creating a interlayer that provides adhesion of the film.
The substrate was sputtered by argon ions for several minutes. The synthesis of the coating includes two-stage deposition.
At the first stage, the films were deposited by an ion beam with a mean energy of about 1.6 keV for 0.5 to 1 hour
to obtain an adhesive interlayer. Then the mean energy of the beam was reduced to 0.3 keV and the deposition
continued for 3.5 hours to maintain the hardness of the coatings. The coating growth rate was ranged from 0.3 to
1.3 A/sec. Adhesion, the bond between the coating and the substrate, obtained is high: there is no detachment while
scratching by the Berkovich diamond nanoindent with a load of up to 50 mn. The hardness is 20 GPa. The film
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Tkachenko O. A., Tkachenko V. A., Baksheyev D. G. Electron Transmission through a Smooth Tunnel Barrier in High-Frequency Field The photon-assisted transmission of an electron through a smooth one-dimensional barrier that simulates the potential in the lower energy subband of the quantum point contact is numerically studied. The dependence of the transmission coefficient on energy shows shoulder-like features, that frequency dependence transforms into maxima. The features are caused by transitions into a channel with the energy close to the top of the barrier when one, two or three photons are absorbed, and their position does not depend of the amplitude of the high-frequency field. With decreasing frequency, the photon-induced steps disappear, but the derivative of the transmission coefficient on energy shows two peaks placed at points lower and higher average height of the barrier on the value equal the amplitude of oscillations. The discovered features can be observed experimentally upon irradiation of a semiconductor structure with a quantum point contact at frequencies 0.01–1.7 THz.
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Tretyakov D. B., Kolyako A. V., Pleshkov A. S., Entin V. M., Ryabtsev I. I., Neizvestny I. G. Investigation of the Statistics of Single-Photon Counting by Two Photodetectors for Applications in Quantum Cryptography A method for revealing a photon-number-splitting attack in quantum-cryptographic communication systems by measuring the photon-number distribution in a laser pulse is proposed. Instead of using a complex photon-numberresolving detector, we propose to use two conventional single-photon detectors based on avalanche photodiodes. The results of experiments on measuring the photon numbers in a laser pulse and their comparison with theoretical calculations are presented. The limits of the applicability of the proposed method are discussed.
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Raman Spectroscopy – 90 Years of Investigations |
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Jersch J., Demokritov S. Complex for Nanoscale Researches by Using TERS, SNOM, BLS, and SPM Techniques We will focus in on our recent developed Complex for nanoscale research with TERS (Tip Enhanced Raman Scattering), SNOM (Scanning Nearfield Optical Microscopy), BLS (Brillouin Light Scattering) and SPM (Scanning Probe Microscopy) techniques, designed in Laboratory of Nonlinear Magneto dynamic (Head Prof. Dr. S. O. Demokritov) in Institute for Applied Physics and Center for Nonlinear Science, University of Muenster. The Complex, built on base of SPM NTEGRA Spectra C (NTMDT) and 6-pass Tandem-Fabry-Perot-Interferometer (JRS Scientific Instruments), designed for nanotechnology research, mainly on spintronic nanostructures.
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Strekal N. D., Askirka V. F., Maskevich S. A. Selection of Raman or Fluorescence Contributions in Chromophores Spectra Near the Surface with Plasmon Properties The observed effect of Raman and fluorescence contribution separation under resonance excitation of chromophores, deposited directly on the surface of plasmonic films or plasmonic crystals is discussed in the frame of influence of nanoparticles sizes and spectral detuning between the frequency of 0-0 transfer of chromophores and resonance excitation of localized plasmons. The contribution of chromophores Raman scattering and fluorescence in the first adsorption layer is discussed in the frame of a size-spectral factor.
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Gaisler V. A., Derebezov I. A., Gaisler A. V., Dmitriev D. V. Luminescence of InAs and AlInAs Single Quantum Dots A system of quantum dots on the basis of AlxIn1–xAs/AlyGa1–yAs solid solutions has been studied. The usage of broadband AlxIn1–xAs solid solutions as the basis of quantum dots makes it possible to expand considerably the spectral emission range into the short-wave region, including the wavelength region near 770 nm being of interest for the design of aerospace systems of quantum cryptography. The optical characteristics of single AlxIn1–xAs quantum dots grown according to the Stranski-Krastanov mechanism are studied by the cryogenic microphotoluminescence method. Hanbury Brown and Twiss experiment has been carried out to measure the photon statistics. Photon correlation function demonstrates a clear photon antibunching effect, what is a direct evidence of single photon emission by AlxIn1–xAs single quantum dots. The fine structure of exciton states of quantum dots is studied in the wavelength region near 770 nm. It is shown that the splitting of exciton states is comparable with the natural width of exciton lines, which is of great interest for the design of emitters of pairs of entangled photons on the basis of AlxIn1–xAs quantum dots.
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Moroz T. N., Goryainov S. V., Ponomarchuk V. A. Structural Peculiarities of Natural Carbonaceous Materials: Raman Spectroscopy Data The structural characteristics of natural carbonaceous materials and their relationship with the formation temperature, sorption properties in rocks with different carbon concentrations studied by the method of nondestructive Raman spectroscopy. Parameters of Raman spectra of the first order, namely, the position and width of the bands, made it possible to separate samples of different genesis. The carbonaceous materials are substantially differed in their structural order both in samples obtained from the same deposit and, to a greater extend, in samples obtained from different deposits.
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Goryainov S. V., Borodina U. O. High Pressure Raman Study of Laumontite Overhydration in Different Water-Containing Media Laumontite overhydration was studied using Raman spectroscopy. Compression in water (up to 9.3 GPa) and in water-alcohol medium (MEW – methanol / ethanol / water 16 / 3 / 1, up to 5.8 GPa) were compared. Sample Ca-Na-K-laumontite from Akhaltsikhe, Georgia was selected. The mineral formula is {Ca2.73Na1.44K1.03(H2O)n} [Al7.93Si16.07O48], where 12< n <18 depending on the humidity and pressure of the medium. By means of Raman spectroscopy, a heterogeneous state of Ca-Na-K-laumontite at P = 0–2.2 GPa in MEW medium was revealed, in contrast to compression in water. An increasing difference between wavenumber/pressure dependencies (2.2–4.5 GPa) related to compression in water and MEW can be ascribed to penetration of additional amount of water in crystal channels during compression in ice VII. A polymorphic transition in laumontite at 4.5–4.8 GPa was also detected. The onset of the disordering laumontite structure was observed at pressure above 8 GPa.
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Chernyshev V. À., Ryumshin V. S. Phonon Spectrum MeF2 (Me = Ca, Sr, Ba, Pb) Cubic and Ortho Phase: ab initio Calculation Ñrystal structure and phonon spectrum of MeF2 crystals (Me = Ca, Sr, Ba, Pb) in both cubic and orthorhombic phases have been investigated. The investigation have been done within the framework of the MO LCAO approach, using hybrid DFT functionals that take into account the contribution of nonlocal exchange in the Hartree – Fock formalism. The frequencies and types of IR and Raman modes are determined. Calculations were carried out in the program CRYSTAL14, designed to simulate periodic structures within the MO LCAO approach.
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Instructions to Contributors |
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