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Nº 8 (2024)

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Articles

Development of a Linear Position-Sensitive Scintillation Neutron Detector Based on ZnS(AG):6Li and Silicon Photomultipliers

Trunov D., Marin V., Sadykov R., Altynbaev E., Glushkova T.

Resumo

A linear position-sensitive neutron detector based on two silicon photomultiplier and an organic light guide has been developed. Determination of the coordinate of the neutron hitting the detector comes from analyzing the amplitude of the signal received from two silicon photomultipliers located at the ends of the light guide. The results of measurements using a collimated 252Cf source and two types of detectors based on silicon photomultipliers from SensL with a diffusion reflector and from Hamamatsu without and with a diffusion reflector are presented. Signals from silicon photomultipliers are recorded using an analog-to-digital converter. The neutron impact coordinates were analyzed using the amplitude characteristics of the photosignal. For a detector based on silicon photomultiplier from SensL, there was no obvious dependence of the signal amplitude on the coordinate of the neutron detection event, in contrast to detectors from Hamamatsu. The resolution of the detector coated with a diffusion reflector was about 10 mm, and without the diffusion reflector it was approximately 5 mm.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):3-10
pages 3-10 views

First Measurements at Neutron Reflectometers TNR and NERO-2

Dyachkov M., Matveev V., Syromyatnikov V., Tarnavich V., Ulyanov V.

Resumo

Paper briefly describes the main units of TNR and NERO-2 neutron reflectometers installed in the hall of horizontal experimental channels of the new high flux PIK-reactor (NRC “Kurchatov Institute”– PNPI) as part of the program for commissioning the first five stations of the instrument base of this reactor. TNR and NERO-2 neutron reflectometers are designed for conducting studies of the magnetic and non-magnetic multilayer nanostructures, including certification of neutron-optical elements for the neutron stations. The TNR has the ability to work in measurement modes with “white” unpolarized/polarized beams and with monochromatic unpolarized/polarized neutron beams (wavelengths from 0.09 to 0.5 nm). NERO-2 is a high-resolution reflectometer with a fixed wavelength and the ability to work with both non-polarized and polarized monochromatic beams. The paper discusses the results of the first measurements of neutron-optical samples on a glass substrates carried out on TNR and NERO-2 reflectometers at the start of the PIK reactor at a power of 7 MW. Measurements were carried out on TNR with a supermirror, which is an aperiodic multilayer nanosystem of 171 pairs of alternating Ni and Ti layers (m = 2.5). On NERO-2, measurements were carried out with a mirror monochromator, which is a periodic multilayer nanosystem of 60 pairs of alternating NiMo and Ti layers with a thickness of 60 Å each.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):11-19
pages 11-19 views

Read-Out System for Thermal Neutron Detectors Based on ZnS(Ag)/LiF Scintillator

Marin V., Trunov D., Litvin V., Sadykov R., Altynbaev E.

Resumo

Neutron scintillation detectors based on ZnS(Ag)/LiF, solid-state photomultipliers, and an organic glass lightguide developed at INR RAS are successfully used in neutron diffractometers facilities at INR RAS as a replacement for standard counters based on 3He. These detectors use optical lightguide with diffuse reflection, which makes it possible to multiply the recorded signal (up to 95 photoelectrons) in comparison with detectors with wavelength shifting fibers. The paper describes 2 types of types of bias circuit for silicon photomultipliers. A method of dynamic bias has been proposed, which makes it possible to reduce the recovery time of a silicon photomultiplier and 8 times increase the loading capacity of neutron detectors. Simulation and comparison of 2 types of preamplifiers showed an increase in the loading capacity. The new electronics makes it possible to increase the loading capacity of the detectors up to 400 kHz. A circuit for digital control of discrimination thresholds has been developed and described. A new data acquisition system for time-of-flight neutron diffractometers for 80 detectors with the possibility of scaling has also been developed.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):20-26
pages 20-26 views

Development of a Vector Magnet Based on High-Temperature Superconductors for Working with Polarized Neutrons

Altynov A., Buzdavin A., Bodnarchuk V., Zhaketov V., Petrenko A., Proyavin M., Chernikov A.

Resumo

Polarized neutron reflectometry is an experimental method for studying metallic thin heterophase layered materials, polymer films, biological systems, free liquide surfaces, and magnetic fluids. It requires experimental equipment that includes a special magnetic system. The described magnetic system, a vector magnet, will allow one to change the direction of the magnetic field in three directions, to place a temperature-control device inside at low and ultra-low temperatures, and will have an aperture that allows one to place a system for detecting neutrons and gamma radiation outside. According to calculations, the cryomagnet will allow the application of a maximum field of up to 3 T in the vertical plane, and of up to 1 T in the horizontal plane. It is proposed to use a 4 mm wide high-temperature superconductor tape to manufacture the vector magnet. A cryostat with a vector magnet will be installed on the REMUR reflectometer on the eighth channel of the IBR-2 reactor.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):27-35
pages 27-35 views

Multiwire Position-Sensitive Neutron Detector with Two Layers of Boron-10

Potashev S., Afonin A., Burmistrov Y., Drachev A., Kasparov A., Karaevsky S., Meshkov I., Ponomarev V., Razin V.

Resumo

Multiwire position-sensitive neutron detector with two layers of boron-10 was developed to detect both thermal and fast neutrons. Sensitive dimensions of two coordinate neutron detector are 50 × 50 mm. New detector characteristics are compared with ones of 100 × 100 mm detector built earlier which we used in neutron flux spatial distribution measurement. Plane-parallel design of new detector has symmetrical structure with respect to wire anode and also includes two intermediate grids and two cathodes made of parallel wires with 2 mm pitch and two silicon substrates coated boron-10 layers of 0.003 mm thickness. Detector geometry, working gas mixture and pressure are chosen so as to ensure full absorption of secondary alpha particle from reaction with thermal neutron within detector gas medium half thickness. Neutron coordinates are determined from measured ionization loss pulse heights produced by secondary nucleus. Detector expected efficiency to thermal neutrons is about 5%. The detector can be used in small-angle and diffraction scattering setups in condensed matter physics.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):36-41
pages 36-41 views

Rotating Magnetic Gravitational Trap for Storing Ultracold Neutrons

Serebrov A., Fomin A., Klyushnikov G., Koptyukhov A., Murashkin A.

Resumo

The paper proposes an experiment to measure the neutron lifetime by storing ultracold neutrons in a rotating magnetic trap. The magnetic trap is a set of NdFeB permanent magnets. By rotating the trap around a horizontal axis, it is possible to carry out gravitational capture of ultracold neutrons and their holding. A design option is presented when two traps are located in one installation on the same axis: material and magnetic. The sensitivity of the magnetic trap was assessed in comparison with the material one under equal measurement conditions. One of the factors influencing the systematic error of the experiment will be the process of neutron depolarization in a magnetic field. Therefore, the paper considers the issue of developing a magnetic system that minimizes the probability of neutron depolarization. The so-called turbine effect is also considered, which can manifest itself in a change in the energy of ultracold neutrons during rotation due to interaction with the flat faces of the trap. The proposed gravitational capture of ultracold neutrons in a magnetic trap is a fundamentally new approach that has never been implemented before. The experiment can be carried out on the ultracold neutron source under construction at the PIK reactor.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):42-49
pages 42-49 views

Relationship of Locally Inhomogeneous, Elastic and Magnetic Fields in Mn–Zn Ferrites

Samoylenko Z., Ivakhnenko N., Pushenko E., Badekin M., Sycheva V.

Resumo

Using the methods of X-ray diffraction analysis, X-ray spectroscopy and theoretical physics, we studied the patterns of changes in the atomic, electronic and magnetic subsystems in ferrites of variable composition MnxZnyFezO4 associated with the formation of clusters differing in the composition of cations. Experimentally detected clusters, which appear in X-ray diffraction patterns as a halo, are characterized by a certain superposition of ion states, the magnetic moment of which depends not only on the spin of the electron, but also on its orbital moment and the spin of the nucleus. A phase transition was discovered in the mesoscopic cluster structure from manganese-containing clusters, caused by the interaction of trivalent manganese ions with oxygen ions, to clusters with a predominance of di- and trivalent manganese ions with oxygen ions. It is found that the clustered structure of manganese-zinc ferrites is responsible for the appearance of extreme magnetic properties; the maximum corresponds to a change in the dominant type of clusters. It is found that with an increase in mass density, a repopulation of energy states occurs as a decrease in the states of the low-energy electron group and an increase in the high-energy Fermi surface in the form of a saddle. It has been established that the peculiarities of condensation of the fundamental and soft modes of complexes (clusters) containing manganese and oxygen ions lead to changes in the physical parameters of the samples.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):50-60
pages 50-60 views

Analysis of the Phospholipid Transport Nanosystem Structure using Small Angle X-Ray Scattering

Maslova V., Kiselev М., Zhuchkov P., Tereshkina Y., Tikhonova E.

Resumo

The structure of aqueous dispersions of phospholipid transport nanosystem (PhTNS) based on soybean phospholipids, developed at the Institute of Biomedical Chemistry (Moscow, Russia), was studied by the method of small-angle X-ray scattering. The PhTNS concentrations in water were 20, 25, 31.25, and 37.5%. The structural parameters of vesicles (inner radius, thicknesses of the regions of hydrophobic tails and polar heads) were determined in the “core multi shell model” approximation with variations in the scattering length densities of vesicle different parts, as well as the solution that was inside and outside the vesicle. A difference in the photon scattering length densities was detected between the solution volume and the inner region of the vesicle, due to the uneven maltose dissolution, which is part of PhTNS. With an almost constant thickness of the lipid bilayer, a decrease in the vesicle radius from ~150 to ~130 Å was observed with increasing concentration of the system which due to increasing osmotic pressure. The hydrophobic volume of vesicles was determined to be 7.45 × 106 Å3 at the lowest concentrations of 20% and 5.85 × 106 Å3 at the highest concentration of 37.5%.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):61-68
pages 61-68 views

Topological Defects in Aggregation of the C60 Fullerene in the Isotactic Polypropylene Matrix

Elnikova L., Ozerin A., Shevchenko V., Nedorezova P., Palaznik O., Ponomarenko A., Skoi V., Kuklin A.

Resumo

Basing on the data of small-angle neutron scattering for the nanocomposite composed of fullerene C60 (16.5 wt. %) in the matrix of isotactic polypropylene, we received information on clusterization of nanoparticles and defined their geometric parameters and dimensionality. In this paper, we propose interpretation of particle aggregation possessing the properties of surface fractal in the size range up to 80 nm observed using small-angle neutron scattering method. Basing on the well-known theories of defect structures of a fullerene molecule C60 in non-Euclidean metrics, in particular, of disclinations and monopole in two-dimensional spherical Gödel space—time, we formulate a lattice version for the action of monopole gas, in which with the lattice Monte Carlo method, using abelian projection, we estimate the energy of monopole currents at different monopole concentrations. In frames of the proposed model, it is possible to calculate fractal properties of the fullerene C60 in a polymer composite and also to interpret evolution of disclinations.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):69-77
pages 69-77 views

Skyrmions and Fluctuations of Spin Spirals in Strongly Correlated Fe1–хCoхSi with Noncentrosymmetric Cubic Structure

Povzner А., Volkov А., Nogovitsyna Т.

Resumo

Strongly correlated Fe1–хCoxSi solid solutions with broken B20-type cubic structure are studied. Within the framework of the spin-fluctuation theory and in the model of the density of electronic states, arising from first-principles calculations within the framework of the generalized gradient approximation taking into account strong Coulomb correlations (GGA+U) temperature transitions are considered in strongly correlated Fe1–хCoxSi alloys (for example, x = 0.2, 0.3) with the Dzyaloshinskii–Moriya (DM) interaction. It is shown that in the compositions under consideration, a first-order magnetic phase transition, which is prolonged in temperature, occurs, during which the sign of the intermode coupling parameter in the Ginzburg–Landau functional changes. It is found that such a transition results in the formation of skyrmion A-phases in limited ranges of temperatures and external magnetic fields, beyond which the experimentally observed fluctuations of spin spirals are realized. The constructed (hТ)-diagrams (which indicate the range of long-range order, fluctuation and skyrmion phases) of Fe1–хCoxSi at x = 0.2 and 0.3 are consistent with the experiment.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):78-84
pages 78-84 views

Comparative Analysis of the Surface Morphology of Dense Membrane Filters Pd95Pb5 and Pd93.5In6.0Ru0.5

Akimova O., Кaminskaya T., Gorbunov S.

Resumo

Features of the dense palladium-based membrane filters surface morphology are studied in this work using atomic force microscopy and scanning electron microscopy methods. Element compositions of the filters are Pd95Pb5 and Pd93.5In6.0Ru0.5 (hereafter numerical coefficients determine the composition in wt.%). The thickness of dense membrane filters is 50 and 70 μм, respectively. Samples from metals of high purity were made by methods of electric arc fusion in a protective atmosphere and cold rolled with intermediate vacuum annealing. Morphology of the filter surface shows differences due to the element composition of the alloys. Manifestations of cavitation in the form of micron-sized funnels were found in palladium doping with lead and the absence of such funnels for palladium alloy with indium and ruthenium. Differences in the surface roughness of the samples are shown. In the mode of contrast of lateral forces, the atomic force microscopy method determined the presence of surface areas of different hardness. The obtained results are important for the choice of material for the manufacture of membrane filters with improved performance characteristics and for the development of the elemental composition of membrane filters in order to optimize their operation in high-tech modern technological processes.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):85-93
pages 85-93 views

Organosilicon Polymeric Acetylene Derivatives: X-Ray Spectral Study and Quantum-Chemical Calculations

Tatevosyan M., Vlasenko V., Shirayeva A., Zhukova T.

Resumo

The atomic and electronic structure of two organosilicon polymers [–Ph2Si(C≡C)2]n (P1) and [–Ph2Si(C≡CC≡C)2]m (P2) (where Ph — is phenyl group) of acetylene and diacetylene types by methods of density functional theory and X-ray emission spectroscopy. The interpretation of X-ray emission SiKβ1-spectra of these polymers was carried out based on an analysis of the distribution of partial electronic states obtained from quantum chemical calculations. Quantitative characteristics of the parameters of the chemical interaction of atoms, such as populations, natural charges, and electronic configurations in the studied polymers, were obtained based on the analysis of hybrid natural bond orbitals. The obtained values of the natural bond orbitals polarization coefficients indicate that the electron density is localized predominantly on carbon atoms. The electronic configurations for carbon atoms in different fragments differ significantly. For C atoms of ethynyl (diethynyl) fragments, they are close to linear σ-bond with sp1.03 (P1) and sp0.95 (P2) configurations, while for C atoms of phenyl fragments it is sp2.42, intermediate between sp2 and sp3 configurations. The natural charges on Si in both polymers are almost the same: +1.58e, +1.59e, while the natural charges on the carbon atoms of the diethynyl group decrease in comparison with the charge on the carbon atom of the ethynyl group from –0.42e to –0.36e.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):94-101
pages 94-101 views

Kinetics of Sodium Borohydride Hydrolysis in Comparison with Ammonia Borane Using Cobalt Catalysts

Dyankova N., Lapin N., Grinko V., Bezhok V., Vyatkin A.

Resumo

The kinetics of the sodium borohydride catalytic hydrolysis with cobalt catalysts Co3O4/ZnO, Co/ZnO, Co3O4/zeolite, Co/zeolite, Co(OH)2, Co3O4, Co–B was studied and the kinetic characteristics of the process were compared with the same characteristics during the catalytic hydrolysis of ammonia borane. The concentrations of sodium borohydride and NaOH in aqueous solution in all cases were 0.064 and 0.06 M, respectively. The apparent activation energy and the rate of hydrogen evolution during the sodium borohydride hydrolysis in the temperature range 35–80°C were determined in each case. Kinetic data were processed using zero-order, first-order, and Langmuir–Hinshelwood reaction models. The apparent activation energies during the sodium borohydride hydrolysis ranged from 37.0 for Co3O4 to 72.6 kJ/mol for Co3O4/ZnO. These values exceeded similar values for the ammonia borane hydrolysis, which were in the range 26.0–47.4 kJ/mol. A higher rate of hydrogen evolution was observed during the sodium borohydride hydrolysis compared to ammonia borane when using these catalysts, except for Co–B and Co/ZnO catalysts. The maximum rates of hydrogen evolution 3510 and 3140 mL H2 (g cat)–1 min–1 were observed when using Co(OH)2 and Co–B catalysts, respectively.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):102-111
pages 102-111 views

Influence of Pulsed Beam-Plasma Impact on a Tungsten–Copper Pseudoalloy in the Plasma Focus Device

Borovitskaya I., Demin A., Epifanov N., Latyshev S., Maslyaev S., Morozov E., Pimenov V., Sasinovskaya I., Bondarenko G., Gaidar A.

Resumo

The results of a study of the combined effect on the W–Cu pseudoalloy of pulsed flows of deuterium ions with a power density qi ≈ 1 × 109 W/cm2 at an exposure duration of τi = 20 ns and deuterium plasma with parameters qpl ≈ 1 × 108 W/cm2 and τpl = 20 ns generated in the Plasma Focus setup “Vikhr” are presented. It is shown that in the implemented mode of irradiation, the nature of the damage to the surface layer of the tested material depends on the state of the surface of the irradiated samples and the number of pulsed impacts of energy flows. The impact of pulsed irradiation on the polished surface of pseudoalloy samples leads to the appearance of extended copper drops on the tungsten surface and to the formation of many pores, which are observed both in Cu drops and in the W matrix. In addition, microcracks appear on the W surface, as well as islands of a copper film of arbitrary configuration. Repeated irradiation of samples of the studied material with an unpolished surface leads to the formation of chains of tungsten droplets located in the upper parts of extended ridges formed during grinding of the original samples. Bursting bubbles are also visible on the irradiated surface, which arose as a result of the boiling of copper inclusions and a copper film deposited on tungsten. Clusters of such bubbles are often localized along ridges on the tungsten surface. The results obtained are discussed using numerical calculations and analysis of the thermal effect on the considered pseudoalloy under pulsed irradiation.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):112-122
pages 112-122 views

Effect of Phosphorus-Containing Dispersant on the Microstructure and Optical Properties of Scintillation Ceramic (Gd, Y)3(Al, Ga)5O12:Ce with Garnet Structure

Karpyuk P., Ermakova L., Dubov V., Lelekova D., Saifutyarov R., Zhdanov P., Malozovskaya M., Komendo I., Sokolov P., Bondarau A., Korzhik M.

Resumo

Phosphoric acid ester, a typical component of commercial dispersants, affects the functional properties of Gd1.494Y1.494Ce0.012Al2Ga3O12 ceramics. In sintered ceramics, the residual phosphorus can reach up to 40–70% of the introduced amount. The admixture of phosphorus located on the surfaces of the particles activates the grain growth during sintering and leads to the formation of secondary phases of rare-earth phosphates. With increasing phosphorus concentration, the density and optical transmittance of ceramics decrease. Relatively small amount of phosphorus can improve the luminescence properties of ceramics, but large amounts can increase phosphorescence and reduce the scintillation light yield.

Poverhnostʹ. Rentgenovskie, sinhrotronnye i nejtronnye issledovaniâ. 2024;(8):123-132
pages 123-132 views