Despite careful optimization, the separation capacity of gas centrifuges (GC) has always been less than the upper limit determined by the Dirac formula. It was recently shown that this limit was greatly overestimated. Nevertheless, the separation capacity of modern GC remains several times lower than the upper limit specified by us. The purpose of this work is to identify the causes of the separation capacity deficit and identify measures that would increase it. Our analysis shows that the suppression of separation occurs in rarefied regions of the gas, where the rate of radial diffusion exceeds the rate of axial convection. This leads to a solid-state concentration distribution and suppression of separation. We assumed that an increase in the density of the mass flow in a sparse region should lead to an increase in the separation capacity of GC. In the direct-flow GC model, we obtained an increase in the separation capacity of the optimal GC to a value only three times less than the Dirac upper limit due to an increase in the density of the mass flow in a sparse region.

In the present work we study dynamics of vacancy-type defects in Fe–Ga alloys (galfenols) with gallium content ranging from 16.5 to 33.0%. At the beginning, a brief overview of the basic properties and crystal structure of Fe–Ga alloys is presented. Positron Annihilation Lifetime Spectroscopy (PALS), Neutron Diffraction and X-Ray Diffraction (XRD) methods show a high degree of correlation in changes in the positron lifetime and phase composition of the samples. A comparison of positron data and the results of structural analysis reveal notably different behaviour of defects ordering in alloys with gallium content x higher and lower than 25%. All the alloys quenched at 1000°C demonstrate high concentration of iron monovacancies (>2 × 10⁻⁴ at⁻¹), and positron lifetime linearly grows from ~160 ps at x = 16.5% to ~180 ps at x = 33.0% (tangent 1.5 ps/1%Ga). The observed changes of the positron lifetime correlate with phase composition of the samples.

The results of a detailed study of the structure and behavior of boron in the specimens of the high temperature nickel superalloy EP741NP produced by the PM HIP technology using the rapidly quenched powder PREP after high-temperature compression tests are presented. Compression tests of cylindrical specimens were carried out at a temperature of 1050°C and strain rates of 10^–3 and 10^–4 s^–1. The method of track autoradiography on boron, in combination with methods of metallography (LM), (SEM), (EDX) and OIM, was used to identify the regularities of influence of changes in structural-phase state during high-temperature deformation on the features of boron distribution. The method of track autoradiography on boron provides an opportunity to study macro-, meso-, and micro-heterogeneity of boron distribution in correlation with the features of the structure-phase state. The effect of dynamic strain aging DSA involving boron in the zone of intensive plastic deformation and the occurrence of dynamic recrystallization DRX with the formation of a “necklace” structure at a deformation rate of 10^–3 s^–1 has been revealed. This effect consists in the intensive migration of boron in the zone of plastic deformation, resulting in the enrichment of the “necklace” area with boron and the decoration of it with dispersed precipitates of M₃B₂ boride phase. A decrease in the strain rate to 10^–4 s^–1 leads to flow instability with the manifestation of the PLC type effect and flow localization with the manifestation of a PLC type serration on the flow curve at the DRX softening stage under conditions of increased heterogeneity of the DRX structure with the formation of PLC type meso shear bands, compared to the DRX “necklace” structure. The revealed effect of DSA involving boron with the formation of meso shear bands PLC-type at the stage of DRX softening is similar to the effect of DSA involving carbon and the formation of PLC-type shear bands decorated with dispersed carbides in nickel-based superalloys and austenitic stainless steels at the stage of work hardening.

Development and application of multilayer semiconductor catalytic nanostructures based on transition metal chalcogenides with a given energy band structure is a promising direction in the hydrogen industry. Electric fields in the contact region of heterojunctions promote separation and accelerated transfer of nonequilibrium light-induced carriers in the volume of photoactive material of nanocatalysts. The paper studies the nanostructure and photocatalytic properties of two-stage MoS₂/WS₂/WSe₂ heterostructures obtained by pulsed laser deposition. A significant increase in the photocurrent in the heterostructure was achieved compared to photocathodes based on individual films included in the heterostructure. The use of highly informative analysis methods (high-resolution transmission electron microscopy, Raman spectroscopy), as well as quantum-chemical calculations using the density functional theory method, allowed us to identify factors that can have an important effect on the functional characteristics of the created heterostructure.

This paper investigates the characteristics of CORC cable as a current carrying element of a superconductor inductive energy storage device. CORC cables based on second generation industrial HTS tapes (RE)Ba₂Cu₃O_7–x produced by S-Innovations with one and two layers of HTS tapes have been wound. The critical current values of the cables in the initial state and after bending deformation were measured at diameters of 50, 40, 23, 15, 10, 5 cm (simulated coil winding). The development of numerical models of CORC cables and analysis of their transport and thermal characteristics have been carried out. Subcritical modes of operation, places of occurrence of possible thermal instabilities of the system have been determined, and recommendations on the operation of elements in the design of a superconducting inductive energy storage device have been given.

In this work we investigate a one-dimensional quantum mechanical model of a single particle with non-trivial dispersion relation in a harmonic potential. The model is motivated by the study of the properties of graphene and accounts for the tunneling between two adjacent Dirac cones in wavenumber space. It is shown that such tunneling leads to the splitting of energy levels even in simple harmonic trap. Results were obtained using two different methods: Monte Carlo simulation and numerical solution of the Schrodinger equation. A potential application of this effect for the creation of two-level quantum systems is discussed.

The paper presents the results of the analysis of pinning mechanisms at the level of separate types of radiation defects during irradiation of exposed YBCO films on a metal substrate with iron ions. It is shown that the introduction of additional pinning centers without large-scale overlapping of potential defect wells leads to an increase in the critical current for columnar and conical defects of various sizes. Depending on the magnitude of the external magnetic field, the relative increase in the critical current of the samples varies from 4 to 47%. Deeper defects lead to better transport characteristics of the superconductor in higher fields. In higher magnetic fields under conditions of weak intrinsic pinning and relatively low anisotropy of superconducting properties, the increase in the critical current of YBCO for columnar defects is several times lower than that for conical defects.

The article presents the results on MNT-CUDA 3.0 verification and validation on full-scale calculations of light-water ZR-6 and ZR-6M and fast-neutron BFS-49/1A critical assemblies. MNT-CUDA 3.0 – a newly developed high-precision engineering code – is aimed at conducting neutron-physical core calculations of various types of nuclear reactors using the multi-group Monte Carlo method. The leverage of graphic processing units’ (GPUs) parallel processing capabilities significantly reduces calculation time. MNT-CUDA 3.0 has a flexible module architecture. Modules of multi-group libraries generation allow to conduct calculations using the data either prepared by the MCU precise code or from multi-group constants library of general purpose ABBN-RF. For full-scale calculations a preprocessor was developed allowing to build a system’s geometry from primitives created by user. It provides the opportunity to describe benchmark models of ZR-6 and BFS critical assemblies without using any significant simplifications. The comparison between multiplication factor calculation results and experimental ones are presented in the paper as well as the discrepancies in flux in every fuel rod, generation rates in every out of 65 energy groups, radial and axial flux distributions between MNT-CUDA calculation results and MCU and MCNP precise codes calculations.

for the problems of development of table-top charged particle accelerators and ion traps of various modifications, quantum-mechanical aspects of the interaction of particles with a potential having movable boundaries are studied. The case of a constant expansion rate of positive and negative potential regions is considered. Using a one-dimensional system as an example, it is shown that the behavior of the de Broglie wave of a particle is determined by the ratio of the potential value and the expansion rate of its boundaries. The results of calculations in MATLAB are given.

In this paper an electrical conductivity in the extended Hubbard model on a hexagonal lattice is computed as a function of the intensity of the electrons’ interaction at neighbouring lattice sites in the region of the phase diagram where the neighbouring interaction and the on-site interaction approximately compensate each other. The study was performed using the Hybrid Monte Carlo method with Hubbard node and link fields. A regular excess of conductivity over a ballistic one was found.

The paper considers a model describing the evolution of the active medium. The model is a cellular automaton with stochastic rules for the transition of a cell from one state to another depending on its state and the states of other cells of the automaton. The model describes the transport of activity in such an environment. It is shown that for certain values of the parameters that define the transition rules, a phase transition from a state of rest to a state of bursts of activity is observed in the behavior of the system. The behavior of the system in the vicinity of the phase transition was studied and it was shown that it exhibits signs of critical self-organization. Automata with different systems of interrelations between cells were studied: both regular lattices and automata with random connections between cells. It is shown that critical behavior is characteristic of all such systems.

 Abstract—In muonic atoms of 238U, nuclei can undergo prompt fission via nonradiative muon transitions: 2p−1s, 3p−1s, 3d−1s, etc. The main features of fission dynamics in prompt fission are studied: barrier increase, saddle-to-scission transition dynamics, muon conversion, and characteristic X-ray emission from fission fragments provide comprehensive information on fission dynamics and fragment properties. The effect of fission suppression in muonic 238U atoms on the GDR shape and the probability of its radiationless excitation in the 3p−1s transitions is demonstrated. A simple interpretation of the energy dependence of the observed GDR width is proposed.

For a hollow cathode discharge in helium, a combined method for obtaining the EEDF by “stitching” its low-energy and high-energy parts is proposed. Each part is determined by applying a filter (Savitzky-Golay or Blackman) with specific parameter values. The dynamic range of the measured EEDF that can be obtained using the method was 4 orders of magnitude. The theoretical EEDF, calculated for experimental conditions, agrees well with the measured one.

In a glow discharge supported by a hollow cathode and a mesh anode, three-dimensional distributions of the parameters of the electronic component of the plasma were obtained for the first time by the Langmuir probe method both in the discharge volume and in the post-anode plasma. It has been experimentally established that the anode glow formed under discharge conditions in this work completely surrounds the anode. A mechanism for plasma formation behind the anode is proposed, when most of the electrons fly around the anode, thus there are curved trajectories of electron movement in the discharge, which ensure their entry into the anode from the opposite side to the cathode.

A two-stream instability for electron beam ion sources (EBIS) is investigated. The dependence of the instability increment on the charge compensation coefficient and on the overlap coefficient of the electron and ion beams at different electron beam energies is determined. An influence of the charge state of Gold and Cadmium ions on the radiative recombination cross section for different electron beam energies is studied. The results of our calculations in MATLAB are given.

The paper presents the results of experimental studies on the use of RF waves in the ion cyclotron resonance (ICR) frequency range for plasma preionization at the small spherical tokamak MEPhIST-0. The conditions of resonant interaction of the ICR wave with plasma particles, as well as the main mechanisms of plasma formation using ICR waves are described. The results of experiments on preionization are presented, in which the generator frequency, the level of the toroidal magnetic field, and the composition of the working gas were varied. It is shown that stable low-temperature plasma can be obtained at the MIFIST-0 tokamak using ICR ionization.

This work is devoted to the first observation of the B+c→J/ψρ+(ρ+→π+π0) decay and determination of the ratio of branching fractions of decays: \mathcal{R} \equiv {{{{\mathcal{B}}_{{{\text{B}}_{{\text{c}}}^{ + } \to {\text{J}}/\psi {{\pi }^{ + }}{{\pi }^{0}}}}}} \mathord{\left/ {\vphantom {{{{\mathcal{B}}_{{{\text{B}}_{{\text{c}}}^{ + } \to {\text{J}}/\psi {{\pi }^{ + }}{{\pi }^{0}}}}}} {{{\mathcal{B}}_{{{\text{B}}_{{~c~{\text{\;}}}}^{ + } \to {\text{J/}}\psi {{\pi }^{ + }}}}}}}} \right. \kern-\delimiterspace} {{{\mathcal{B}}_{{{\text{B}}_{{~c~{\text{\;}}}}^{ + } \to {\text{J/}}\psi {{\pi }^{ + }}}}}}}, which is found to agree with theoretical predictions. The mode B+c→J/ψπ+ is used as a normalization channel. Decay channel B+→J/ψ(K*+→K+π0) is used to control potential mass resolution effects. The intermediate state of the π⁺π⁰ system is found to contain mainly a ρ⁺ component in accordance with QCD factorization model predictions. The study was carried out by analyzing the data collected from 2011 to 2018 in proton-proton collisions corresponding to an integrated luminosity of 9 fb^–1 at c.m. energies of 7, 8 and 13 TeV by the LHCb spectrometer.

The paper presents diagnostics of high-energy ions (more than 1 MeV per particle) emitted in the axial direction from a laser-induced spark discharge in the pinching mode at a current of up to 80 kA and an energy input of up to 120 J. A characteristic feature of the discharge is the rapid increase in current to its maximum value within a time of ≈100 ns. To initiate the discharge, a YAG:Nd⁺³ laser with an energy of 150 mJ and a duration of 10 ns was used, the radiation of which was focused on a high-voltage electrode made of cobalt. Using the time-of-flight collector technique, up to 10¹⁰ cobalt ions were recorded per pulse in a solid angle of 0.04 rad. Calculations were performed and a model of a mass spectrometer was developed, optimized for an experiment to register fast highly charged cobalt ions.

The multiple small-angle scattering of neutrons has been analyzed taking into account the pseudomagnetic interaction. A kinetic equation that is valid in the principal order for scattering at one scattering center has been derived. It has been shown that the spin part of neutron scattering with the collinear orientation of the initial polarization of neutrons and nuclei is determined by the average value of the pseudomagnetic nuclear field, and field fluctuations lead to neutron depolarization.

The results of the analysis of pulse-height distributions measured during the registration of the DT-neutrons by a detector with a diamond sensitive element are presented. It is shown that a three-component representation should be used to describe the response function of the considered detector.

In the framework of the dispersion approach to the axial anomaly, both Abelian and non-Abelian cases are considered. Anomalous sum rules for isovector, octet and singlet currents are derived, which allow us to relate the experimentally observed quantities, the transition form factors π0,η,η′→γγ(∗), with the non-perturbative gluon matrix element ⟨0|GG˜|γγ(∗)⟩. A description of this matrix element is obtained as a function of the photon virtuality in various kinematic regions.

The stability of the determination of particle size distributions using model small-angle scattering intensity from mixtures of polydisperse spherical and cylindrical particles has been analyzed. It is shown that when using a parametric distribution model, the probability of obtaining the correct nonlinear least squares solution decreases when the range of starting parameter values is expanded, and the scatter of solutions corresponding to local minima of the target function increases. Ambiguity of solutions occurs in most cases with overestimations of the average size of cylindrical particles and their polydispersity compared to the exact solution. To avoid the minimization target function falling into local minima, a good starting approximation is required, within 50% of the relative detuning of the model parameters from their exact values.