Table of contents

This paper is a preface to the proceedings of the XXX International Conference on Interaction of Intense Energy Fluxes with Matter, which was held in Elbrus settlement, in the Kabardino-Balkar Republic of the Russian Federation, from March 1-6, 2015.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

We studied the shock-wave and ablation phenomena in tantalum films of submicron thicknesses irradiated by femtosecond laser pulses. The single-shot spectral interferometry was used for continuous diagnostics of movement in a picosecond range both the frontal and rear surfaces of a sample. Measured displacement histories were converted into surface velocity histories. As a result, the new data on shear and tensile strength have been obtained for solid and molten tantalum at strain rate ∼ 10⁹ s^-1.

Spallation phenomena in graphite targets were investigated experimentally under nano- and picosecond shock-wave action at laser facilities "Kamerton-T" (GPI RAS) and PHELIX (GSI). In the range of strain rates of 1 to 10 μs⁻¹ at the first time, data of dynamic tensile strength of the material were obtained. At maximal realized strain rate of 14 μs⁻¹, the spall strength value 2.1 GPa has been achieved that is 64% of the theoretical ultimate tensile strength of the graphite. Spallation was observed not only on the backside of the target, but also on its front (irradiated) surface. The morphology of the front and rear surfaces of the targets was studied using the optical and scanning electron microscopy. The structure of the graphite in irradiated area on the facial side as well as in the spallation zone on the rear side of the target was investigated by Raman scattering method. A comparison of the dynamic strength of the graphite with the dynamic strength of a synthetic diamond is done.

Femtosecond laser irradiation of a thin gold film deposited on the thick glass substrate is considered. The thickness of a film has the order of a few microns and focal focal spot is small. Underlying physics of processes after irradiation is studied with combined approach of two-temperature hydrodynamic and MD simulations. Found are two adsorbed fluence thresholds F_s < F_a and three regimes of motion, in comparison with the freestanding film. There is oscillatory mode when the film oscillates remaining on substrate for 0 < F < F_s. For F_s < F < F_a the film breaks away from substrate because negative pressure overcomes the cohesion strength of the film-substrate contact. For F_a < F there is inner disruption of the film happened before the separation of metal from dielectric substrate.

The permittivity of Lorentz plasmas and wide-range expression for effective frequency of collisions of electrons are considered in wide temperature range. The proposed expression fulfills all limiting cases (high- and low-frequency skin effect, degenerate and nondegenerate plasmas) and permits one to incorporate different physical phenomena in warm dense matter like contribution of electron-phonon collisions and umklamp process to permittivity. For the case of aluminum plasmas, the model takes into account both intraband and interband contributions to permittivity via semi-empirical Huttner model modified in such a way to ensure proper description of optical properties of aluminum at room temperatures.

This paper presents the results of three-dimensional (3D3V) particle-in-cell modeling of the interaction of a femtosecond laser pulse with a two-dimensional inhomogeneous plasma corona of subcritical density. It was shown that in the presence of sufficiently steep temporal pulse edge the excitation of plasma waves, electron trapping and generation of collimated beams of accelerated electrons with energy of about 0.2-0.5 MeV may occur. The simulation results are compared with experiments on the generation of collimated beams of accelerated electrons from metal targets irradiated by intense femtosecond laser radiation.

The generation of hot electrons at grazing incidence of a subpicosecond relativistic-intense laser pulse onto the plane solid target is analyzed for the parameters of the petawatt class laser systems. We study the preplasma formation on the surface of solid Al target produced by the laser prepulses with different time structure. For modeling of the preplasma dynamics we use a wide-range two-temperature hydrodynamic model. As a result of simulations, the preplasma expansion under the action of the laser prepulse and the plasma density profiles for different contrast ratios of the nanosecond pedestal are found. These density profiles were used as the initial density distributions in 3-D PIC simulations of electron acceleration by the main P-polarized laser pulse. Results of modeling demonstrate the substantial increase of the characteristic energy and number of accelerated electrons for the grazing incidence of a subpicosecond intense laser pulse in comparison with the laser-target interaction at normal incidence.

Plasma created by femtosecond laser pulse of high intensity can be used as the brilliant source of high energy electrons, ions and x- or γ-rays. In most cases, laser pulses with high contrast are used for particle acceleration. But, it has been shown, that changing parameters of pre-plasma layer on the surface of the target can significantly increase electron energies. In this work we present the results of the experimental and numerical studies of the abnormally hot electron generation mechanisms in the case of long scale pre-plasma layer subcritical density.

The results of a study of structure and mechanical properties of welding joints, superconducting characteristics of the material after joining of welded components of superconducting radio frequency cavities are presented. The paper also describes the results of testing of the RF 1.3 GHz single-cell niobium cavity manufactured in the PTI NAS Belarus.

Investigation of the polymeric material properties under powerfull energy flux impact is relevant as for basic research (mathematical modeling of polymeric materials behavior in extreme conditions, testing the state equations), as for practical applications (for testing of protective coatings for space research and laboratory facilities). This paper presents the results of experimental studies of the interaction of polymeric materials with a relativistic electron beam produced by a high-current electron accelerator Calamary. Calamary facility provides a wide range of electron beam parameters: diameter 10-15 mm, the voltage on the diode up to 300 kV, the current through the diode up to 30 kA. New method of beam-target interaction area measurement was developed. The original method for the mechanical kick impulse measuring based on piezoelectric vibration sensor was presented. The dependence of the kick impulse from the power flux was obtained.

The metal behavior under the action of high-current electron irradiation is an example of a complex problem with a large number of involved physical processes. In this paper, we develop a continuum model of dynamic fracture of a metal melt in the energy absorption zone of a high-current electron beam and present a two-dimensional version of this model. The 2D model is necessary for the description of the action of a narrow-focused electron beam on matter. Fracture of copper and aluminum in the molten state in the energy absorption zone of the electron beam is numerically simulated, and the spatial distribution of the droplet size is investigated. Action of a high-current electron beam with the electron energy of about 1 MeV leads to the formation and subsequent breakup of the melt to droplets with diameters from 0.5 μm to several tens of micrometers. The finest droplets (0.5-5 μm) are generated in the center of the energy absorption zone, while the droplet sizes increase up to several tens of micrometer at the edge of the energy absorption zone, where matter is colder. Keeping the melt in a metastable (expanded and overheated) state provides a tension wave with an amplitude of about 3-4 GPa following the shock wave and propagating deep into the target.

On the basis of a set of critical parameters, we construct and study the phase diagram of sodium chloride at sufficiently high temperatures and pressures.

The results of theoretical and experimental study of the nanocomposites laser ablation have been used to predict its optical strength dynamics under laser irradiation. A practical application of statistical regularities observed in the laser ablation destruction of materials using Weibull-Gnedenko three-parameter statistics has been proposed.

The study of detonation-like mode of laser induced damage propagation is presented. This mode is new investigation object of laser destruction of silica-based optical fibers. The fiber destruction images were obtained in evolution and in static (on saved samples).

The goal of this paper is experimental study of the mechanism of initiation of secondary explosives (SE) by short laser pulse. Laser initiation of SE is much more difficult in comparison with initiation of primary explosives. Using of some special methods is typically requested to realize laser initiation of SE: using of porous SE, putting it in a closed envelope, and using some optically dense additives. In this paper we consider interaction of laser pulse with open surface of non-porous, optically uniform SE. Only pure chemical methods were used to control the light sensitivity of SE. Implementation of the method of laser initiation is reduced to the optimization of composition and molecular structure of the explosives, along with the optimization of the laser pulse (its duration, energy density and wavelength).

This paper is devoted to the development of the technique to estimate a distribution of the mechanical stress on the strained specimen based on the data about terahertz absorption. This hypothesis is based on the relation between density of the stressed body and absorption of THz radiation. Using the experimental setup developed by the NeTHIS the authors estimate the stress distribution near the holes with different diameters in stressed polymeric foams. The experimental results are in a good agreement with the numerical simulation of foams deformation process.

In the project of Advanced European Infrastructures for Detectors at Accelerators (AIDA), the Institute of Nuclear Research designed and tested the Totally Active Scintillator Detector (TASD). This paper reports the results of design of TASD prototype and outlines requirements for a test beam at CERN to test these, tentatively planned on the H8 beamline in the North Area, which is equipped with a large aperture magnet. TASD consists of 50 modules of plastic scintillators. Each module is instrumented with one X and one Y plane, with 90 scintillator bars per plane. The bar width, height and length are 1.0 cm, 0.7 cm and 90 cm respectively. The distance between modules can be varied from 0 to 2.5 cm. Other components such as active detectors or passive sheets of material can be inserted in these 2.5 cm gaps if required. The full detector depth can therefore be varied from 75 cm to 200 cm and in its compact form, it is 1 m³ in volume. The paper presents measurement results for the TASD elements that included in the prototype elements (measurement of crosscurrents, the light yield of scintillators, and the characteristics of photodiodes).

The spectra and decay time of pulsed cathodoluminescence (PCL) of a scintillating crystals excited by the electron beam is compared to the spectra and decay time of the luminescence of the same crystals initiated by γ-rays (GL). It is shown that spectra and decay time of PCL and GL are identical within the experimental errors. The explanation of these results is based on taking into account the physical processes within the crystal media under the irradiation by high-energy particles. The results of this study confirm that the PCL method may be used for the rapid analysis of the luminescent properties of scintillators.

In the fields of gamma-neutron radiation the accuracy measurement of gamma- ray doses depends on their sensitivity to concomitant neutron radiation. In this connection, verification results of gamma-dosimetry on the installation with isotope cobalt or cesium sources are not always adequate to measurement results in real gamma-neutron fields. The data prove, that the sensitivity coefficients of gas-discharge gamma-dosimeters at PRIZ-M reactor is 1.23 larger as compared to Co⁶⁰ source, due to the effect of the concomitant neutrons on their indications. The error due to the neutrons effect can be significantly reduced or eliminated completely, if gamma-dosimeters calibrated in the field of gamma-neutron radiation, adequate spectral and dose characteristics to radiation fields in which they are used.

Development of neutron generators using plasma focus (PF) chambers is being conducted in the All-Russia Scientific Research Institute of Automatics (VNIIA) during more than 25 years. PF is a source of soft and hard x-rays and neutrons 2.5 MeV (D) or 14 MeV (DT). Pulses of x-rays and neutrons have a duration of about several tens of nanoseconds, which defines the scope of such generators—the study of ultrafast processes. VNIIA has developed a series of pulse neutron generators covering the range of outputs 10⁷–10¹² n/pulse with resources on the order of 10³–10⁴ switches, depending on purposes. Generators have weights in the range of 30–700 kg, which allows referring them to the class of transportable generators. Generators include sealed PF chambers, whose manufacture was mastered by VNIIA vacuum tube production plant. A number of optimized PF chambers, designed for use in generators with a certain yield of neutrons has been developed. The use of gas generator based on gas absorber of hydrogen isotopes, enabled to increase the self-life and resource of PF chambers. Currently, the PF chambers withstand up to 1000 switches and have the safety of not less than 5 years. Using a generator with a gas heater, significantly increased security of PF chambers, because deuterium-tritium mixture is released only during work, other times it is in a bound state in the working element of the gas generator.

The one-dimensional problem on two-sided irradiation by proton beams of the plane layer of condensed DT mixture with density ρ₀ = 100ρ_s, where ρ_s is the fuel solid-state density at atmospheric pressure, is considered. The effect of the plasma self-radiation on the thermonuclear burn-up factor as well as the role of the inverse Compton effect are studied. It is shown that the inverse Compton effect decreases the burn-up factor down to about 3% while the plasma self-radiation in whole decreases it down to about 9%.

Mathematical modelling of radiative and gas-dynamic processes in substances at high energy density is carried out for experiments, where both laser and heavy ion beams are used. Important features of the theoretical model, known as the ion model (IM), which is used for quantum mechanical calculations of radiative opacity, are discussed. Reliability of (IM) results is tested with experiment, where measurements of x-pinch radiation energy yield for two exploding wire materials, NiCr and Alloy 188 were made. Theoretical estimations of radiative efficiency are compared with experimental results, and (IM) calculations agree well with the experimental data. Subsequently, the theoretical approach was used for temperature diagnostics of CHO plasma target in combined laser-heavy ion beam experiments. Joint radiative and gas-dynamic calculations are performed for comparison with experiment, where hohlraum radiation transmits through the CHO plasma target, and the share of absorbed radiation energy is compared with experiment. Study of radiative properties of CHO plasma with little admixture of gold is carried out as well. Specific dependence of the Rosseland mean on plasma temperature is discussed for gold plasma.

The Spectr-W³ information-reference system was developed in 2001-2013 and realized as an online Web resource based on the factual atomic database Spectr-W³. The information accumulated in the Spectr-W³ atomic database contains about 450,000 records and includes the experimental and theoretical data on ionization potentials, energy levels, wavelengths, radiation transition probabilities, and oscillator strengths, and the parameters of analytical approximations of electron-collisional cross-sections and rates for atoms and ions. Those data were extracted from publications in physical journals, proceedings of the related conferences, special-purpose publications on atomic data, provided directly by authors. The information is supplied with references to the original sources and comments, elucidating the details of experimental measurements or calculations. To date, the Spectr-W³ atomic database is still the largest factual database in the world, containing the information on spectral properties of multicharged ions. In 2014, the new stage in the development of the Spectr-W³ atomic database started. The purpose of this stage is the creation of a new information section of the Spectr-W³ database. This section would contain the information on the x-ray emission spectrograms registered from various plasma sources.

This paper studies the influence of inertial gases admixtures (Ar, Kr, Xe) to deuterium in plasma focus (PF) chambers. Experiments were realized in PF chambers with discharge currents of 350, 650 and 1000 kA. The measurements of the hard x-ray (HXR) emission were carried out by the scintillation detector SSDI38 with time resolution of 2.5 ns. Experiments show the existence of optimum amount of inertial gases, which corresponds with the atomic number of added gas. At the optimum amount of inertial gas and deuterium in PF chamber, the HXR yield rises up to 10 times in comparison with HXR yield only for deuterium filling. This work shows the dependence of HXR emission on PF device stored energy. The mechanism of inertial gases admixtures influence that leads to rise of HXR yield has been discussed. The mechanism concerns with different behavior of deuterium ions and ions of inertial gases during the pinch decay phase when the discharge current compression force has reduced. Inertial gas ions locate near the axis of the pinch and deuterium ions go to the near plasma area. Local positive charge in plasma forms on this axis because of multiply charged ions of inertial gases. Then electrons gather to the axis area and electron density increases. This electrons form high current electron beam under the influence of the induced electromotive force during the pinch decay phase. HXR emission is generated after the electron beam interaction with the anode target in PF chamber.

The energy of electromagnetic radiation (the black body radiation) is generalized for the system containing an ultra-relativistic fully ionized plasma. It is shown that the radiation energy depends monotonically on one dimensionless characteristic parameter, which includes particle density and plasma temperature.

DD neutrons from microfusion in the interelectrode space of a table-top low energy nanosecond vacuum discharge with a deuterium-loaded Pd anode have been demonstrated earlier. The detailed particle-in-cell (PIC) simulation of the discharge experimental conditions have been developed using a fully electrodynamic code. The principal role of a virtual cathode and the corresponding deep potential well (PW) formed in the interelectrode space are recognized. The PIC modeling has allowed identifying the scheme of small-scale experiment with a rather old branch of plasma physics as inertial electrostatic confinement fusion. Deuterons being trapped by this well are accelerating up to the energies of a few tens of keV that provides the DD nuclear synthesis under head-on collisions. Meanwhile, any ions of other elements like He, C, O, Si (as main elements of different shells of stars) being placed in the PW (even with low Z charges) have to be accelerated easily up to the head-on collisions energies, which are corresponding to the temperatures of ignition T_ign for different shells. We conclude that hypothesis on some imitation of different stages of stellar nucleosynthesis by nuclear burning in the potential well of virtual cathode in vacuum discharge seems to be reasonable and stimulating in the future study of complex element burning including advanced fuel like p-B¹¹.

In this paper, we continue the discussion of the experimental results on the yield of DD neutrons and hard x-rays in the nanosecond vacuum discharge (NVD) with a virtual cathode, which was started in the previous article of this issue, and previously (Kurilenkov Y K et al 2006 J. Phys. A: Math. Gen.39 4375). We have considered here the regimes of very dense interelectrode aerosol ensembles, in which diffusion of even hard x-rays is found. The yield of DD neutrons in these regimes is conditioned not only by the head-on deuteron-deuteron collisions in the potential well of virtual cathode, but also by the channel of "deuteron-deuterium cluster" reaction, which exceeds overall yield of neutrons per a shot by more than an order of magnitude, bringing it up to ∼ 10⁷/(4π). Very bright bursts of hard x-rays are also represented and discussed here. Presumably, their nature may be associated with the appearance in the NVD of some properties of random laser in the x-ray spectrum. Good preceding agreeing of the experiment on the DD fusion in the NVD with its particle-in-cell (PIC) simulations provides a basis to begin consideration of nuclear burning "proton-boron" in the NVD, which will be accompanied by the release of alpha particles only. With this objective in view, there has been started the PIC-simulation of aneutronic burning of p-B¹¹, and its preliminary results are presented.

Spherically bent crystals are widely used in focusing monochromators, spectrometers and other x-ray optical systems. In particular, they are used in focusing spectrometers with spatial resolution, applied in high energy density diagnostics and warm dense matter studies. In this case, plasma parameters are obtained via measurements of relative intensities of characteristic spectral emission lines for multiply charged ions, which are affected by an instrumental function. Here we develop and use the ray-tracing computer simulations to study reflectivity properties of spherically bent crystals in a particular experimental conditions and to provide the method to adjust and validate the measured spectral line intensities on quantitative basis.

Modeling an irradiation process of a copper plate for studying the formation and evolution of point defects, that are vacancies and interstitials, is presented in this work. The point defects formation energies were estimated for fcc Cu using molecular dynamics simulation. These values were applied at calculations of atomic concentrations of vacancies and interstitials by numerically decision of kinetic equations. The results of molecular dynamics simulation showed that the interstitial formation energy is more than the vacancy formation energy. These values are in satisfactory agreement with the experimental data. The results of calculations of atomic concentrations of defects confirmed that interstitials are more mobile and their absorption by stocks is more intense.

Atomic resonance absorption spectroscopy has been used to study the yield of molybdenum atoms in the process of ultraviolet laser pulse photo-dissociation of Mo(CO)₆ vapor. Molybdenum atoms in a ground state were formed by the quenching of the electronically excited Mo atoms generated during photolysis and were detected using the resonance absorption at a wavelength of 386.41 nm. The effective quenching rates were measured in the presence of various bath gases.

Effect of torrefaction on consumer characteristics of fuel pellets made of low-grade and agricultural waste is shown. Data on the volatile content, ash content, calorific value and hygroscopicity for initial pellets and pellets, heat-treated at various temperatures are presented. The experimental study of the combustion process of initial and heat-treated pellets showed that torrefaction of pellets leads to a decreasing of the ignition temperature and an increasing of the efficiency of boiler plant.

The paper presents results of simulation of a process for the two-stage thermal conversion of wood biomass into the synthesis gas. The first stage of process is pyrolysis of raw materials, the second stage is cracking of volatile pyrolysis products which blown through the char at a temperature of about 1000° C. Char is a porous biomass residue with carbon content about 90%. The simulation based on the results of experimental investigations of a pilot plant with capacity up to 50 kg of raw material per hour. The main result of simulation is estimation of an energy conversion efficiency of wood biomass into synthesis gas for three different operation modes. The first mode is conversion of biomass into fuel gas and char, and the char is not further used. The second mode is the same, but char used as fuel for producing heat for own demand of the process. The third mode includes gasification of char by means of water steam, aimed to obtaining an additional yield of synthesis gas. The simulation shown, that total efficiency of power plant was 17.1% in the first mode, 22.4% in the second mode and 22.6% in the third mode.

The experimental investigations of pyrolysis process sewage sludge at different conditions are presented. As a result of executed investigations it was shown that syngas (mixrure of CO and H₂) used in gas engine can be obtained in pyrolysis process.

For the synthesis of high pressure phases from natural minerals and the shock wave treatment of fluid bearing phases a halide based method was developed. The experiments were performed in the pressure range between 25 and 162 GPa with a success rate for the new method of 100% for the new method. Based on the Impedance Corrected Sample Recovery Capsule under avoiding the adiabatic decompression a direct comparison between different loading paths and sample holder geometries is possible. The recovered samples show neither indications of melting in the case of kaolinite and very limited degassing in the case of carbonates. The recovery of amorphous water bearing Al-Si-phases with Aluminum in four-, five- and six-fold coordination was possible. The samples were analyzed with scanning electron microscopy, x-ray diffraction, nuclear-magnetic-resonance- and infra-red-spectroscopy and the results were directly compared.

A series of experiments was carried out to investigate the relaxation properties of glycerol under shock-wave loading. The strain rates at the compression wave front were in the range of 10⁵-10⁷ s^-1. A modified version of the wire explosion set-up was used. Free surface velocity profiles were recorded by VISAR with fiber-optic sensor. We found that the glycerol exhibits the non-Newtonian liquid behavior: viscosity is higher at the high strain rate. Strain rate at the compressive wave front is found to be dependent on the wave amplitude in power of 1.3.

The behavior of docosane (C₂₂H₄₆) and cerium (Ce) under shock-wave action has been investigated. It was shown that the solid docosane demonstrate elastic-plastic properties and has abnormal compressibility at pressures below 100 MPa. It was found that the strength of docosane remains practically constant and equals to about 24 MPa when passing through the melting point. We determined the shear stress and evolution of compression wave in the area of cerium anomalous compressibility. The value of longitudinal stress at which the γ-α phase transition occurs is also determined. It is shown that the phase transition pressure, under dynamic and static compression coincides and is equal to 0.8 GPa. The spall strength of cerium rises from 0.3 to 0.7 GPa when strain rate increase from 2.1 x 10⁴ to 1.02 x 10⁶ s^-1.

This paper is devoted to the problem of development and optimization of schemes for explosive compaction of mixtures of solid powder materials with metal bond. For this purpose, experiments were conducted on explosive compaction of mixtures of tungsten carbide (WC) and cobalt (Co) using a simple cylindrical compaction system. In addition, a numerical simulation of shock waves propagation in two-phase porous medium WC+Co was carried out. Based on experimental and numerical studies of shock wave propagation, the optimal modes of explosive compaction of two-phase powder media, representing mixtures of solid powder materials with metal bond, were found. It is shown that the most preferable compaction mode for obtaining a uniform durable compact of a mixture of powders WC+Co with ratio 9:1 by volume in axially symmetric scheme with central mandrel corresponds to the detonation velocity of 4.6 km/s followed by sintering.

The experiments on explosive compaction of Ni and Al micron powders mixtures in cylindrical recovery assemblies are reported. Synthesized NiAl compacts were characterized by optical microscopy and x-ray diffraction. The found porosity of the compacts was decreasing with dynamic pressure growth. The geometry of dendrite NiAl grains was associated with the dynamics of pressure waves inside the assembly.

In the paper, the behavior of ice and natural limestone under explosion condition was investigated. The objects of study were the river ice and natural limestone quarry on Siberia. The practical significance of research due to the need to increase production of oil and gas in permafrost regions, the fight against ice jams, etc. We organized a mobile laboratory ''Explosive destruction of the natural materials" at the National Research Tomsk State University. The main purpose of the laboratory is express analyzing of explosive destruction of natural materials. The diameters and depths of explosive craters in the limestone and explosive lane in the ice were obtained. The results can be used to test new models and numerical methods for calculating shock and explosive loading of different materials, including ice.

A mixture of powdered Al and Al₂O₃ has been subjected to a shock-wave pressure of ≈ 170 kbar, followed by vacuum-encapsulating and quenching of the product to liquid nitrogen. The ac magnetic susceptibility measurements of the samples have revealed metastable superconductivity with T_c ≈ 37 K, characterized by glassy dynamics of the shielding currents below T_c. Comparison of the ac susceptibility and the dc magnetization measurements infers that the superconductivity arises within the interfacial granular layer formed between metallic Al and its oxide due to the shock-wave treatment.

The paper presents a multi-line diagnostic system for measuring the surface velocity in shock physics experiments. This system is designed for simultaneous measurement of surface velocity at multiple points. It is free from ambiguity caused by harmonic dependence of interference signals on the velocity and has a time resolution of 0.8 ns.

In this paper, we investigate the dynamic shear strength of perfect monocrystalline metals using the molecular dynamics simulation. Three types of deformation (single shear, uniaxial compression and tension) are investigated for five metals of different crystallographic systems (fcc, bcc and hcp). A strong dependence of the calculated shear strength on the deformation type is observed. In the case of bcc (iron) and hcp (titanium) metals, the maximal shear strength is achieved at the uniaxial compression, while the minimal shear strength is observed at the uniaxial tension. In the case of fcc metals (aluminum, copper, nickel) the largest strength is achieved at the pure shear, the lowest strength is obtained at the uniaxial compression.

A computational plasticity model with accounting of coupled evolution of the dislocations and twins in metals under the dynamic loading is presented. The model is based on our previous results for the dislocation plasticity, but generalizes them and accounts mechanical twinning in addition. It includes equations of the mechanics of continua for elastic-plastic medium, where the plastic deformation tensor is determined through the structural defects evolution in the material. The model is self-consistent and allows determining of mechanical properties in wide range of strain rates and thermodynamic conditions as well as modification of the defect subsystems. The equations and parameters, its numerical implementation and some of obtained results are presented.

Experimental methods of observation of early stage of shock-induced ejecta from metal surface with micrometer-sized perturbations are still limited in terms of following a complete sequence of processes having microscale dimensions and nanoscale times. Therefore, simulations by the smoothed particle hydrodynamics (SPH) and molecular dynamics (MD) methods can shed of light on details of micro-jet evolution. The size of simulated sample is too restricted in MD, but the simulations with large enough number of atoms can be scaled well to the sizes of realistic samples. To validate such scaling the comparative MD and SPH simulations of tin samples are performed. SPH simulation takes the realistic experimental sizes, while MD uses the proportionally scaled sizes of samples. It is shown that the velocity and mass distributions along the jets simulated by MD and SPH are in a good agreement. The observed difference in velocity of spikes between MD and experiments can be partially explained by a profound effect of surface tension on jets ejected from the small-scale samples.

The paper deals with modeling the high-speed impact of metal plates. In one-dimensional formulation, we numerically solve equations of continuum mechanics, supplemented by equations of dislocation plasticity, twinning and fracture models. The thermodynamic state of matter is described by means of interpolation equations of state. A comparison with experimental data in the form of velocity profiles of the free rear surface of a target is presented. Dynamics of shock waves in thin metal foils is numerically investigated.

Using the Maxwell model of viscoelastic medium, we numerically investigate the influence of the viscoelastic properties of polymethylmethacrylate on the variation of the shock wave amplitude with depth. Parameters of the Maxwell model are chosen by comparison with experimental data on the high-speed impact of plates in order to fit the modeling results with the experimentally measured profiles of the free-surface velocity. A caloric equation of state is used to calculate the pressure from density and internal energy. It is shown that at the limit of weak shock waves, the accounting of the viscoelastic properties allows one to achieve a better agreement between calculated and experimental data for the magnitude of the shock wave velocity in comparison with the case of hydrodynamic calculations. Using the viscoelastic and hydrodynamic approaches, we investigated the dynamics of shock waves in polymethylmethacrylate initiated by micro-, nano- and picosecond pulses of pressure on the sample surface. The calculation results show that the changes in the shock wave amplitude with depth are approximately identical in the hydrodynamic and viscoelastic cases.

We investigate regularities of the shock wave propagation and fracture in the Al-Cu composite under high-current electron irradiation. A model of multiphase medium mechanics is used, which takes into account the finite rate of stress relaxation between phases, the heat transfer, and the relative motion and friction between components. The multiphase medium model is supplemented by the models of plasticity and fracture. The presence of inclusions in the matrix significantly influences the generation and propagation of stress waves in the irradiated target. In addition, molecular dynamics calculations of tensile strength are performed, which show that the presence of copper inclusions reduces the strength of the material. The reason for softening is the stress concentration near the inclusion, rather than the weak adhesion between copper and aluminum.

This work presents results of integrated experimental and numerical study of destruction of reinforced concrete beam made of concrete and fiber concrete under shortterm dynamic loading. Experimental studies were carried out using pile driver. Short-term dynamic loading acting on a beam was applied by falling weight, 450 kg, from the height 700 mm. The value of dynamic load in experiments was defined by means of force gauge, linear displacement transducers were used to define linear displacements. Numerical simulation was held three-dimensionally within phenomenological approach of continuum mechanics, the reinforcing elements were clearly defined. Finite element method was modified to solve dynamic tasks. Impact of load on a beam in calculations was replaced by impulse. The dependence of impulse on time was defined from the experiment. The influence of reinforcement on deformation and beam destruction was studied. Correlation of experimental and numerical data was performed.

This paper presents results of numerical simulation of interaction between aircraft Boeing 747-400 and protective shell of nuclear power plant. The shell is presented as complex multilayered cellular structure comprising layers of concrete and fiber concrete bonded with steel trusses. Numerical simulation was held three-dimensionally using the author's algorithm and software taking into account algorithms for building grids of complex geometric objects and parallel computations. The dynamics of stress-strain state and fracture of structure were studied. Destruction is described using two-stage model that allows taking into account anisotropy of elastic and strength properties of concrete and fiber concrete. It is shown that wave processes initiate destruction of shell cellular structure—cells start to destruct in unloading wave, originating after output of compression wave to the free surfaces of cells.

The paper is discussing problems connected with embedment of the incubation time criterion for brittle fracture into finite element computational schemes. Incubation time fracture criterion is reviewed; practical questions of its numerical implementation are extensively discussed. Several examples of how the incubation time fracture criterion can be used as fracture condition in finite element computations are given. The examples include simulations of dynamic crack propagation and arrest, impact crater formation (i.e. fracture in initially intact media), spall fracture in plates. Applicability of the approach to model initiation, development and arrest of dynamic fracture is claimed.

In this paper dynamic fracture process due to high-speed impact of steel plunger into ceramic sample is simulated. The developed numerical model is based on finite element method and a concept of incubation time criterion, which is proven applicable in order to predict brittle fracture under high-rate deformation. Simulations were performed for ZrO₂(Y₂O₃) ceramic plates. To characterize fracture process quantitatively fracture surface area parameter is introduced and controlled. This parameter gives the area of new surface created during dynamic fracture of a sample and is essentially connected to energetic peculiarities of fracture process. Multiple simulations with various parameters made it possible to explore dependencies of fracture area on plunger velocity and material properties. Energy required to create unit of fracture area at fracture initiation (dynamic analogue of Griffith surface energy) was evaluated and was found to be an order of magnitude higher as comparing to its static value.

This experimental study is devoted to the electric and optical phenomena, that becomes apparent during the combustion of the two-layer heterogeneous energetically-condensed solid-phase systems with the (Zr+CuO+LiF)/(Zr+BaCrO₄+LiF) structure. It was found that such systems combustion is accompanied by an electric pulse signal generation with duration ∼ 1.0 s at half-width and the maximal amplitude 1.2-1.5 V. The signal arises at the combustion beginning and is continuing to the reaction completion. For the mentioned systems it was firstly registered a flame optical emission from the reaction zone within the visible spectral region (λ ∼ 300-700 nm). The initial (green) mixtures and combustion products were explored by x-ray diffraction and scanning electron microscopy. The combustion experiments were carried out by using a home-made experimental mounting, allowing in on-line regime to record the physical parameters of the energetically-condensed systems during a combustion process.

Chemically prepared metal nanopowders are normally pyrophoric, i.e. are liable to ignite spontaneously on exposure to air because of high reactivity and developed specific surface. On the other side, reliable theoretical models for spontaneous self-ignition of fine dispersed powders at room temperature have not been suggested so far. A deeper insight into the mechanism of the phenomenon would shed new light on the critical conditions for self-inflammation and thus would provide some clues for optimization of the passivation of fine dispersed powders. In this work, we formulated and analyzed an entry-level model for ignition of pyrophoric powders. Analysis of such a model in terms of the ignition theory gave the following results. Depending on the width of the reaction zone, the ignition may get started in either one or two stages. The duration of each stage was evaluated by using the approximate methods of combustion theory. The parametric limits for the model applicability were derived and the influence of sample length on the ignition process was explored as well.

Using a laser interferometer VISAR the measurements of the particle velocity profiles in detonation waves for nitromethane/methanol mixtures with additions of a sensitizer diethylenetriamine were conducted. It is shown that the detonation front in a mixture of nitromethane/methanol is unstable and sensitizer is an effective method for the flow stabilization. If the diluent concentration is less than 10%, the detonation front is stabilized by adding of 1% diethylenetriamine. At higher concentrations of methanol, the sensitizer does not reject instability, but the amplitude of oscillations decreases in several times. An increase of the limit concentration of methanol at the addition of diethylenetriamine to the mixture was found.

Based on the assumption of the existence of the partial chemical equilibrium in the detonation products, an approximate method for calculating composition of the detonation products is developed. The method uses the assumption of the existence of extremum of Helmholtz free energy for a given density, temperature, and molecular weight of the detonation products mixture. Without significant loss of accuracy to the solution of stiff differential equations, detailed kinetic mechanism can be replaced by one differential equation and a system of algebraic equations. This method is always consistent with the detailed mechanism and can be used separately or in conjunction with the decision of a stiff system, replacing it when bimolecular reactions are near equilibrium.

A multicomponent equation of state with wide range of applicability is required to simulate shock waves in C_xN_yO_z mixtures. This problem demands fine molecular interaction model due to competition between repulsion and attraction forces during shock compression process. A self-consistent Ornstein-Zernike application (SCOZA) based on distribution function integral equation theory can be used for it. The hypernetted-chain/soft core mean spherical approximation (HMSA) for SCOZA has been successfully applied to dense fluid systems with ambidextrous interactions. However, it was not designed to simulate mixtures, such as shock products of C_xN_yO_z system. The convenient way to simulate multicomponent systems is the van der Waals one-fluid model (vdWlf). It has been shown, that vdWlf is not good enough for CO₂ shock products at pressures higher, than 50 GPa. The multicomponent HMSA closure application based on partial version of the virial theorem has been offered in this paper. It is verified by molecular Monte-Carlo simulation at pressures up to 160 GPa with accuracy about 1–2%.

We present results of the classical molecular dynamics simulation of detonation initiation in simple AB model of a high explosive compressed by ultra-short shock wave (SW). The simplified reactive empirical bond order potential (REBO) defines interatomic forces in the AB model explosive made up of diatomic AB molecules. Simulation of ultra-short piston-driven compression of AB explosive with duration of picoseconds represents an indirect initiation via a thin metal foil irradiated by a femtosecond laser pulse. We studied transition of SW to a detonation wave (DW), including evolution of calculated pressure profile in a sample. A run distance to detonation of such AB explosive film, which is required for detonation initiation, was obtained. Variation of loading time and piston velocity gives a 2D region of transition from SW to DW. The influence of pores on detonation initiation threshold is discussed.

In experiment influence of the acoustic impact on streams reacting and nonreacting gases is investigated. Visualization of streams was carried out by a shadow method on the basis of the shadow IAB-451 device. It is revealed that in some cases at acoustic impact on a gas stream bifurcation of a stream is observed. Dependences of a corner of disclosure of a stream and distance are received from the open end of a tube to a place of division of a stream from the frequency of acoustic influence and level of sound pressure.

An influence of haloalkanes CF₃H and CCl₄ (known as inflammation and explosion suppressors) on combustion and pyrolysis of acetylene behind shock waves was experimentally studied. While ignition delay times in stoihiometric acetylene-oxygen mixtures were expectedly increased by halogenoalkanes admixtures, the induction times of carbon particle formation at acetylene pyrolysis were dramatically reduced in presence of CCl₄. A simplified kinetic model was suggested and characteristic rates of diacetylene C₄H₂ formation were estimated as a limiting stage of acetylene polymerization. An analysis of obtained data has indicated that promoting species is atomic chlorine forming in CCl₄ pyrolysis, which interacts with acetylene and produces C₂H radical, initiating a chain mechanism of acetylene decomposition. The results of kinetic modeling agree well with experimental data.

Problems related to the autoignition of hydrogen-air mixtures are highly important for the operation safety of nuclear reactors and for hydrogen power engineering. In spite of extensive studies in this area, there are still many problems directly concerned with the ignition delay times of H₂/O₂ mixtures and with the conditions under which these processes occur. This paper deals with the numerical analysis of the data available in the literature on O, H, and OH yields in order to determine the influence of the primary channels of the initiation of H₂/Air mixtures. The numerical modeling of the available literature data on the ignition delays of hydrogen-air mixtures made it possible to describe the shock tube measurements of ignition delays within the framework of a unified kinetic mechanism over a temperature range of 930-2500 K at pressures from 0.1 to 8.7 MPa.

The specific features of the combustion waves propagating through the channels filled with chemically active gaseous mixture and non-uniformly suspended micro particles are studied numerically. It is shown that the heat radiated by the hot products, absorbed by the micro particles and then transferred to the environmental fresh mixture can be the source of new ignition kernels in the regions of particles' clusters. Herewith the spatial distribution of the particles determines the features of combustion regimes arising in these kernels. One can highlight the multi-kernel ignition in the polydisperse mixtures and ignition of the combustion regimes with shocks and detonation formation in the mixtures with pronounced gradients of microparticles concentration.

The aim of the paper was to analyze the structure and the stability of the chocked flames to understand the origins of different possible combustion modes, including quasi-stable supersonic flames and deflagration-to-detonation transition. By means of numerical analysis, it is shown that the chocked flame structure and its stability are defined by two basic mechanisms: compression of the fresh mixture ahead of the flame front and compression of the reacting mixture inside it. The first mechanism provides burning velocity increase; the second one can either accelerate or decelerate reaction depending on the pressure-dependent reaction behavior in the observed pressure range and depending on the rate of compression. In case of reaction intensification with rising pressure, a detonation forms on the leading edge of the flame front. Otherwise, the flame propagates in a quasi-stable supersonic regime consisting of consequential stages of deceleration and re-acceleration of the flame. On the deceleration stage, the compressed fresh mixture priorly chocked by the supersonic flow near the flame tip flows downstream generating the compression wave ahead. The new contact surface between this packet of compressed mixture and the fresh mixture ahead of the flame front can become the kernel of the exothermal reaction, evolving in a new deflagration wave or even detonation.

Features of the unsteady flames propagating in channels filled with gaseous combustible mixtures are studied numerically. The analysis is based on the model treating the flame as a moving energy source. It is shown that the crucial role in flame dynamics and its structure evolution belongs to the compression waves emitted by non-steady flame itself. The compression waves establish flow pattern, temperature and pressure fields near the flame front, which in turn determine the features of flame evolution on the different stages of its propagation.

We propose a new conceptual approach for direct detonation initiation in the gaseous mixtures seeded with micro particles via the radiative heating from the external energy source. The basic mechanisms of energy absorption, ignition and detonation formation are analyzed numerically on the example of hydrogen-oxygen mixture. Obtained data is very promising and allows us to formulate conditions for the source power to ignite detonation in certain system geometry.

A process of deflagration-to-detonation transition in propane-butane-oxygen and acetylene-oxygen mixtures, in an open channel with a circular cross section with a diameter of 3 mm, was investigated experimentally. Detonation initiation was carried out by burning the mixture in the prechamber connected to the channel. The prechamber was considered as an extended source for the initiation of the detonation of a finite volume. To measure the velocity of a flame front, photodiodes, installed along the axis of the channel, were used. To determine the boundary conditions at the entrance to the channel, a piezoelectric pressure transducer was used. The influence of the dimensions of the prechamber, equivalence ratio and fuel on the pressure profile, and evolution of the flame front along the axis of the channel are presented. It was shown that, the dynamics of the flame front and shock waves in the channel can occur in different scenarios depending on the geometry of the prechamber and equivalence ratio. Two limit effects of the prechamber detonation initiation in the channel have been analyzed. The pre-detonation distances and the minimal energy of direct initiation of the detonation were determined.

Influence of an ejector nozzle extension on gas flow at a pulse detonation engine was investigated numerically and experimentally. Detonation formation was organized in stoichiometric hydrogen-oxygen mixture in cylindrical detonation tube. Cylindrical ejector was constructed and mounted at the open end of the tube. Thrust, air consumption and parameters of the detonation were measured in single and multiple regimes of operation. Axisymmetric model was used in numerical investigation. Equations of Navies-Stokes were solved using a finite-difference scheme Roe of second order of accuracy. Initial conditions were estimated on a base of experimental data. Numerical results were validated with experiments data.

Formation of an overdriven detonation wave in methane-oxygen mixtures in a channel was investigated experimentally The gas mixture was ignited by a spark gap, located at the closed end of the combustion chamber. To create the overdriven detonation wave, a decay of the stationary detonation wave in the transition to a channel with a larger cross-section was carried out. Then, a complex of a shock wave and flame front moved into the channel with converging section. Formation of the overdriven detonation wave with parameters several times greater than those of the Chapman-Jouguet detonation was recorded at the outlet of the conical section. The velocities of the detonation front depend upon the composition of the mixture.

Using of sound-absorbing surfaces to weaken and decay of a detonation wave in hydrogen-air mixtures was investigated experimentally. Experiments were carried out in a cylindrical detonation tube open at one end. Initiation of the explosive mixture was carried out by a spark discharge, which is located at the closed end of the detonation tube. Acoustical sound absorbing foam element of a specific weight of 0.035 g/cm³ with open pores of 0.5 mm was used. The degree of attenuation of the intensity of the detonation wave front was determined.

The process of the issuing of a supersonic jet from a flat tapered nozzle has been investigated with two values of ratio of isobaric to isochoric specific heats (γ = c_p/c_V) and different parameters NPR (nozzle pressure ratio) on the basis of numerical modeling. NPR parameter represents the ratio of the pressure at the nozzle inlet to the pressure in the environment. As a result the solid state grid model have been created for the numerical simulations of the flow of gas inside the nozzle and jet formation of compressed gas from the nozzle, which can be used to analyze the data structure. For the same value of the parameter NPR, but at a smaller value of γ an intersection point shifts further away from the inlet section of the nozzle. The flow separation becomes substantially less.

By means of particle image velocimetry method shock-wave boundary layer interaction on the pre-heated ramp surface was investigated. The influence of surface heating on separation region unsteadiness was proved. It was found experimentally that increasing of wall to outer flow temperature ratio raises amplitude of separation region oscillation.

Development of novel hypersonic technologies necessarily requires the development of methods for analyzing a motion of hypervelocity vehicles. This paper could be considered as the initial stage in developing of complex computational model for studying flows around hypervelocity vehicles of arbitrary shape. Essential part of the model is a solution to three-dimensional transport equations for mass, momentum and energy for the medium in the state of both LTE (local thermodynamic equilibrium) and non-LTE. One of the primary requirements to the developed model is the realization on the modern heterogeneous computer systems including both CPU and GPU. The paper presents the first results on numerical simulation of hypersonic flow. The first problem considered is three-dimensional flow around curved body under angle of attack. The performance of heterogeneous 4-GPU computer system is tested. The second problem highlights the capabilities of the developed model to study heat and mass transfer problems. Namely, interior heat problem is considered which takes into account ablation of thermal protection system and variation of the surface shape of the vehicle.

The paper presents the modified method for the supersonic nozzle profiling with respect to non-monotonic dependence of adiabatic index on temperature, as well as the results of nozzle profile calculation for two sets of input parameters, based on independently determined specific heat curve for molecular nitrogen N₂ and products of its thermal decomposition in the temperature range of T = 260-100000 K and atmospheric pressure.

A new implicit velocity-pressure split method is discussed in the given presentation. The method implies using conservative velocities, obtained at the given time step, for integration of the momentum equation and other convection-diffusion equations. This enables simulation of super- and hypersonic flows with account of motion of solid boundaries. Calculations of known test cases performed in the FlowVision software are demonstrated. It is shown that the method allows one to carry out calculations at high Mach numbers with integration step essentially exceeding the explicit time step.

With the use of the author's theoretical model are discussed geological structures which can be created by fallings of galactic comets on terrestrial planets: Mercury, Mars, Earth, Venus and the Moon. The model predicts that depending on combination of a number of conditions galactic comets may form on these planets following types of structures: craters, diatremes, lava sheets, volcanoes, dome-shaped surface uplift, as well as coronae and montes (on Venus). The main factors that influence on origin of these structures on planets are (i) density of gas shell, (ii) thickness of planetary lithosphere, (iii) composition and degree heating of lithosphere rocks, (iv) frequency of fallings galactic comets. We are discussing specific features of these structures on the Moon, Mars, Earth and Venus.

The refined semiclassical method based on the Thomas-Fermi statistical model takes into account the shell effects by means of an additive correction. The method has been verified in the calculations of a plasma equation of state at high temperatures. To expand its application range to low temperatures some assumptions are revised that have been made to obtain the simple formula for a shell correction. The validity of the assumptions is discussed and the results of their refusal are analyzed. As examples, a number of single-particle states in the ideal plasma of a few elements with strongly differing atomic numbers is calculated.

Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atoms in their unit cell: tI11* in Bi, Sb, As, Ba, Sr, Sc and tI19* in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au₃Cd₅-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere-Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.

The collective dynamic phenomena accompanying the collision of high-energy heavy ions are suggested to be approximately described in the framework of ideal relativistic hydrodynamics. If the transition from hadron state to quark-gluon plasma is the first-order phase transition (presently this view is prevailing), the hydrodynamic description of the nuclear matter must demonstrate several anomalous wave phenomena—such as the shock splitting and the formation of rarefaction shock and composite waves, which may be indicative of this transition. The present work is devoted to numerical study of these phenomena.

Thermodynamic consequences of subdivision for all first-order phase transitions (PT) into enthalpy- and entropy-driven ones (H-PT and S-PT), proposed previously [arXiv:1403.8053], are under discussions. Key-value for proposed discrimination is main benefit (decreasing) in enthalpy or (nega)entropy in spontaneous phase decomposition, i.e. the sign of latent heat of PT and consequent slope of its P(T)-dependence. The main driving mechanism for many isostructural S-PT is the decay (delocalization) of some kind of bound complexes, e.g. atoms, molecules etc. Thermodynamic features of H-PT and S-PT differ significantly. Entropic PT are always the part of more general thermodynamic anomaly—domain where great number of usually positive second cross derivatives (e.g. Grüneisen parameter, thermal pressure coefficient etc.) became negative simultaneously. This domain is restricted (in the case of isostructural S-PT) by remarkable bound, where all mentioned second derivatives are equal to zero. Isostructural S-PT has more complicated topology of stable, metastable and unstable states and their boundaries—binodals and spinodals in comparison with ordinary enthalpic PTs. Two new thermodynamic objects accompany isostructural S-PT: (i) appearance of third (additional) region of metastable states with positive compressibility, isolated from the regions of stable states; (ii) appearance of new additional spinodal, topped with a new singular point, separating metastable and unstable states. These additional spinodal and singular point obey to relation (∂P/∂V)_T = ∞. All thermodynamic anomalies of entropic PTs correspond to conclusive and transparent geometrical feature of such PTs: multilayered structure of thermodynamic surfaces for temperature, entropy and internal energy as pressure- density functions U(P, V), S(P, V) and T(P, V).

The simplest model for non-congruent phase transition of gas-liquid type was developed in frames of modified model with no associations of a binary ionic mixture (BIM) on a homogeneous compressible ideal background (or non-ideal) electron gas /BIM(∼)/. The analytical approximation for equation of state equation of state of Potekhin and Chabrier of fully ionized electron-ionic plasma was used for description of the ion-ion correlations (Coulomb non-ideality) in combination with "linear mixture" (LM) approximation. Phase equilibrium for the charged species was calculated according to the Gibbs-Guggenheim conditions. The presently considered BIM(∼) model allows to calculate full set of parameters for phase boundaries of non-congruent variant of phase equilibrium and to study all features for this non-congruent phase transition realization in Coulomb system in comparison with the simpler (standard) forced-congruent evaporation mode. In particular, in BIM(∼) there were reproduced two-dimensional remarkable ("banana-like") structure of two-phase region P — T diagram and the characteristic non-monotonic shape of caloric phase enthalpy-temperature diagram, similar to the non-congruent evaporation of reactive plasma products in high-temperature heating with the uranium-oxygen system. The parameters of critical points (CP) line were calculated on the entire range of proportions of ions 0 < X < 1, including two reference values, when CP coincides with a point of extreme temperature and extreme pressure, X_T and X_p. Finally, it is clearly demonstrated the low-temperature property of non-congruent gas-liquid transition — "distillation", which is weak in chemically reactive plasmas.

The results of calculations of thermodynamic properties of aluminum under shock compression in the framework of the Thomas-Fermi model, the Thomas-Fermi model with quantum and exchange corrections and the Hartree-Fock-Slater model are presented. The influences of the thermal motion and the interaction of ions are taken into account in the framework of three models: the ideal gas, the one-component plasma and the charged hard spheres. Calculations are performed in the pressure range from 1 to 10⁷ GPa. Calculated Hugoniots are compared with available experimental data.

The pressure–volume–temperature equations of state have been constructed by combining experimental data and semiempirical estimations for a number of compounds recently synthesized under extreme pressure–temperature conditions. The solids with various bonding types were considered: covalent hard and superhard boron-rich and diamond-like compounds (e.g. B₆O, B₁₃N₂, BP, c-BC₅, and nano-cBN), ionic semiconductors (e.g. Mg₂C and Mg₂C₃), as well as intercalation compounds (e.g. clathrates Na₄Si₂₄ and Na_24+xSi₁₃₆), and simple substances (e.g. boron allotropes γ-B₂₈ and t'-B₅₂, and open-framework silicon allotrope o-Si₂₄ with quasi-direct bandgap). We also showed how the reliable p-V-T equations of state may be constructed using different types of data available.

A caloric model, which describes the pressure-density-internal-energy relationship in a broad region of condensed-phase states, is applied for tungsten. As distinct from previously known caloric equations of state for this material, a new form of the cold-compression curve at T = 0 K is used. Thermodynamic characteristics along the cold curve and shock Hugoniots are calculated for the metal and compared with some theoretical results and experimental data available at high energy densities.

Study of thermodynamic parameters of magnesium in the near-critical point region of the liquid-vapor phase transition and in the region of metal-nonmetal transition was carried out. Measurements of the electrical resistance of magnesium after shock compression and expansion into gas (helium) environment in the process of isobaric heating was carried out. Heating of the magnesium surface by heat transfer with hot helium was performed. The registered electrical resistance of expanded magnesium was about 10⁴-10⁵ times lower than the electrical resistance of the magnesium under normal condition at the density less than the density of the critical point. Thus, metal-nonmetal transition was found in magnesium.

New method for calculation of critical point parameters and binodal of vapor-liquid (dielectric-metal) phase transition is suggested. Method is based on the hypothesis that cohesion, which determines the main properties of solid state, determines also the properties in vicinity of critical point. Comparison with known experimental data for rare gases and mercury shows satisfactory agreement with our calculations.

Here we suggest semiempirical equations of state defining the behavior of some solid metals at pulsed energy flows impact. A new wide-range two-phase equation of state of metals is proposed. These equations have few free parameters. They are estimated for Na and Cu. Melting curves of metals are defined within both one-phase approximation using Lindeman criterion, and two-phase-approximation. Volume and entropy discontinuities are calculated as a function of pressure at melting curve for Na and Cu. We also compared all the simulations results to the available experimental data for these metals.

As part of a unified system of the few-parameter equation of state, an approach is implemented to calculate the mechanical properties of materials behind the front of strong shock waves. For aluminum and copper, the results of calculations are compared with the experimental data available for high energy densities; a close match is observed.

In this work, the model of thermodynamic and transport properties of copper and gold at electron-ion non-equilibrium state is presented. Accepted here ranges of electron temperature and pressure are enough to describe the experimentally achievable states. The changes in electron spectra due to electron heating and compression or expansion are taken into account using two-parabolic model. In our previous works, thermal conductivity and electron-ion coupling were considered as dependencies on electron and ion temperatures. Now the dependence on density for these coefficients is taken into account. To include exchange-correlation effects on electron-electron collisions we have found out how this effect can be included in electron screening. In addition, we have renewed our approach for heat conductivity calculation to include thermoelectric phenomena, which are significant at high electron temperatures. The effect of electron heating on sound velocities in aforementioned metals is investigated. The two-temperature hydrodynamics simulation of film expansion was provided with the use of the model presented here.

Data on thermal conductivity in states with hot electrons are necessary for the calculation of ultrashort laser exposure and the behavior of matter near the tracks of fast particles penetrating the condensed phase. The paper presents new analytical expressions describing the state of gold with the extra-high heat conductivity within a broad range of two-temperature phase diagram including the melting curve. This is a region in the threedimensional space defined by the electron temperature T_e, ion temperature T_i and the density ρ, at which the thermal conductivity κ is one order of magnitude larger than the value related to the room temperature. The growth of heat transfer is due to a sharp increase in the heat capacity of carriers (electrons) when they are heated and, accordingly, the gradual loss of the degeneracy. The developed model is based on an exact solution of the kinetic equation, involving experimental data and calculations of the electronic spectrum by the density functional method. The model works well also at low temperatures T_e that allows describing the crystallization of the melt as it cools down.

Within the inhomogeneous electron gas theory, a model is considered for calculations of static polarizability of matter. The analysis confirms the high accuracy of the new model. Among the main advantages of the model are its simplicity and physical transparency, as well as lack of computational problems.

This work covers an ab initio calculation of transport and optical properties of plastics of the effective composition CH₂ at density 0.954 g/cm³ in the temperature range from 5 kK up to 100 kK. The calculation is based on the quantum molecular dynamics, density functional theory and the Kubo-Greenwood formula. The temperature dependence of the static electrical conductivity σ_1DC (T) has an unusual shape: σ_1DC(T) grows rapidly for 5 kK ≤ T ≤ 10 kK and is almost constant for 20 kK ≤ T ≤ 60 kK. The additional analysis based on the investigation of the electron density of states (DOS) was performed. The rapid growth of σ_1DC(T) at 5 kK ≤ T ≤ 10 kK is connected with the increase of DOS at the electron energy equal to the chemical potential ɛ = μ. The frequency dependence of the dynamic electrical conductivity σ₁(ω) at 5 kK has the distinct non-Drude shape with the peak at ω ≈ 10 eV. This behavior of σ₁(ω) was explained by the dip at the electron DOS.

The experimental data on graphite melting temperature remain poorly determined despite the long history of investigations. The experimental results cover the wide span from 3800 to 5000 K that is an essentially larger uncertainty than the errors of individual experiments. In this work, we deploy the molecular dynamics method and expand our previous study of the kinetics of graphite melting comparing different carbon interatomic potentials. Here we consider the melting front propagation rate, the aspects of defect formation and single graphene layer decay. The results obtained allow us also to discuss the aspects of graphite-vapor and possible graphite-carbyne phase transitions at low pressures.

Quenching of liquid carbon (T = 6600 K) on a cold diamond substrate at T = 300 K in conditions close to the experimental laser melting of dispersed graphite on the substrate of natural diamond is investigated using molecular dynamics (MD) simulations. Quenching was carried out for two types of boundary conditions on the side opposite to the diamond substrate. The simulations confirmed the experimental result of the formation of amorphous carbon under such conditions. The calculations showed that the destruction of the diamond substrate did not take place because of its very high thermal conductivity. The estimation of the cooling rate of liquid carbon was done, the result is 10¹⁵ K/s. Temperature profiles in different layers of liquid carbon were restored to reproduce the detailed picture of the quenching process. We evaluated the radial distribution functions (RDF), the distribution of carbon atom bond fractions sp¹-sp²-sp³, the average bond length and the azimuthal angles distributions for amorphous carbon atoms. This analysis confirmed that the amorphous carbon obtained by quenching in MD-simulations had a graphite-like structure.

Phase transition in uranium mononitride (UN) at high pressure has been studied using molecular dynamics. At low pressure, UN has the cubic structure like NaCl (with the space group Fmm). The research based on Gibbs energy calculation shows that cubic UN turns into rhombohedral face-centered structure (with the space group Rm) at pressure about 32 GPa. It is shown that parameters of Rm-structure change at increasing of the pressure. At various pressures, the parameters of structures with isotropic stress tensor are different.

A multi-scale model of the tensile fracture of metal melts is developed based on a combination of molecular dynamics (MD) simulations and continuum description of kinetics and dynamics of voids; the model considerably extends the time and length scales of MD. Nucleation of voids due to thermal fluctuations is taken into account. Growth of a void in melts is well described by the Rayleigh-Plesset equation, while in the case of a solid metal we propose a dislocation-based model of the void growth. Based on the MD simulations, we investigate the nucleation rates in the uniform monocrystalline metals and metal melts, dynamics of pre-existing voids and compare them with the continuum model (equations of nucleation and growth). Using of the literature data on the surface tension and viscosity of melts allows us to get a correspondence between the continuum description and MD. With the use of the model, we calculated the strength of the uniform melts of Al, Cu, Ni, Pb, Fe and Ti within a wide range of strain rates (from 10³-10⁴ to 10⁹-10¹¹ s^-1) and temperatures (from melting temperature to 70-80% of critical temperature). Calculations show that the tensile strength of homogeneous melts decreases slowly with the strain rate decrease. As a result, within the range of strain rates of 10⁶-10⁸ s^-1, a homogeneous nucleation mode can be realized, in which the dynamic strength of a melt can be comparable to, or even higher than the strength of a solid metal.

In this work, we investigate the initiation of fracture in an aluminum sample with the help of molecular dynamics simulations. The critical negative pressures in different simulated regions as a function of the system size and initial structure are obtained. Tension in regions with defect structures, such as initial voids or dislocations and vacancies, leads to a decrease in tensile strength. In case of initial voids, a decrease in the ratio of the void radius to the system size causes an increase in the system's tensile strength, while rising temperature causes a linear drop of tensile strength. We propose a continuum dislocation based model of nanovoids growth to describe the critical negative pressure in systems with a void. Nucleation of dislocations near a growing void is taken into account with the Arrhenius-type law for the nucleation rate.

Effect of high pressure induced spin crossover on the magnetic, electronic and structural properties of the minerals forming the Earth's low mantle is discussed. The low temperature P, T phase diagram of ferropericlase has the quantum phase transition point P_c = 56 GPa at T = 0 confirmed recently by the synchrotron Mössbauer spectroscopy. The LDA+GTB calculated phase diagram describes the experimental data. Its extension to the high temperature resulted earlier in prediction of the metallic properties of the Earth's mantle at the depth 1400 km < h < 1800 km. Estimation of the electrical conductivity based on the percolation theory is given. We discuss also the thermodynamic properties and structural anomalies resulting from the spin crossover and metal-insulator transition and compare them with the experimental seismic and geomagnetic field data.

A possibility of formation of novel carbon phases from graphite at continuous exposure under pressures of 18 GPa to 45 GPa at room temperature was examined. Features in the pressure dependence of resistance as well as its relaxation times were found in the range 27-35 GPa. The scanning electron microscope image of the sample subjected to the pressure of 45 GPa shows the inclusion of a new phase, which did not disappear after removal of the load. However, the new phase is poorly seen in the pressure dependence of resistivity because of shunting by a large amount of non-transformed graphite.

We report on our study of electrical resistance of double-walled carbon nanotubes (DWCNTs) at pressure up to 30 GPa. High pressure has been generated in the diamond anvil cell with conductive synthetic diamonds. We detect a decrease in DWCNTs resistance with increasing pressure and correlate the results with the corresponding structural transformations. Analysis of the DWNTs Raman spectra confirms the irreversible structural changes.

This paper discusses the influence of high pressures (up to 50 GPa) on the electrical properties of the polycrystalline materials (InSe)_x(CuAsSe₂)_1-x, x = 0.05 and 0.5. It was found that, for each compound, features in the pressure dependence of all the physical parameters of interest occur in the same pressure intervals, which can be due to structural transitions and a change in the electron structure.

Samples of high pressure perovskite-like phases CaCu₃Ti_4-xV_xO₁₂, x = 0.1, 0.2, 0.3, 0.4 and 0.5 were synthesized at high-pressure and high-temperature conditions in a toroid-type high-pressure chamber. Their electrical properties were studied by impedance spectroscopy in the frequency range from 1 Hz to 30 MHz at temperatures of 300 to 600 K and at pressures of 10 to 30 GPa.

This work demonstrates experimental possibility of investigation of high refractory materials around its melting point, particularly in premelting region with high accuracy. In this article authors describe the developed experimental setup based on rapid resistive self-heating of a sample by a large current pulse generated by a capacitor discharge circuit that allow fast pulse interruption by temperature feedback signal. The sample temperature was measured with a two-channel microsecond radiation pyrometer. Preliminary experiments were conducted on tantalum and molybdenum at heating speed of 10⁸ K/s. The method allows investigating thermophysical properties of refractory conductive materials such as melting temperature, melting heat, specific resistivity, specific enthalpy and specific heat capacity in solid and liquid phase, especially in premelting area.

Numerical simulation of the experiment of Korobenko et al (2007 Phys. Rev. B 75 064208) in strongly coupled plasma of aluminum have been fulfilled. The results of numerical simulation and the experiment are compared. It is established that the hydrodynamic flows in the experiment can be assumed one-dimensional. The elastic-plastic effects in the dynamics of aluminum foil are also insignificant. The focus in the modeling is devoted to the study of the dynamics of the thermodynamic states of aluminum and their spatial homogeneity. It is emphasized the strong influence of the thermal conductivity for such experiments.

Two methods for determining of the true (thermodynamic) temperature via thermal radiation spectrum of an opaque heated object are presented. The first method is based on the relative emissivity. It is shown that in many cases, the range of the true temperature values may be narrowed down using the "convex-concave" criterion. As shown, that any relative spectral emissivity dependence can be approximated by the same parametric model. The second method is based on the use of the Wien displacement law for real materials. This method is effective when the radiation of the object close to the gray-body radiation in the region of the spectral emission maximum. It is shown that these two methods complement each other.

In present work, phase transitions in strongly-coupled two-dimensional dissipative Yukawa systems are studied. The thermodynamic characteristics of these systems are calculated, namely the internal energy, the specific heat and the entropy. The considered characteristics have two singular points; one of these points corresponds to the first-order phase transition from crystal to the hexatic phase, and another point corresponds to the second-order phase transition from the hexatic phase to the isotropic liquid. The dependence of the position of the melting lines and the range of existence of the hexatic phase on the concentration of the grains in the considered system is studied. The special attention is paid to the comparison of our results to the existing numerical and analytical data.

Numerical analysis of development of vortex cascades in a three-dimensional inviscid shear layer depending on the method of determining and the value of artificial viscosity is done. At the developed stage of turbulence the spectral analysis of kinetic energy is carried out and the law -5/3 of Kholmogorov is confirmed. Pulsation and correlation functions of the flow are investigated.

An analytical solution for the capillary oscillations of the charged drop in dielectric medium obtained with taking into account the damping due to viscosity. The model has been applied for the estimation of even-even spherical nuclei surface tension and nuclei viscosity. Attenuation factor to nuclear capillary oscillation frequency ratio has been found.

Viscosity and diffusion are chosen as an example to demonstrate the universality of diagnostics methods in the molecular dynamics method. To emphasize the universality, three diverse systems are investigated, which differ from each other drastically: liquids with embedded atom method and pairwise interatomic interaction potentials and dusty plasma with a unique multiparametric interparticle interaction potential. Both the Einstein-Helfand and Green-Kubo relations are used. Such a particular process as glass transition is analysed at the simulation of the aluminium melt. The effect of the dust particle charge fluctuation is considered. The results are compared with the experimental data.

Molecular modelling is used to calculate transport properties and to study relaxation of liquid n-triacontane (C₃₀H₆₂). The problem is important in connection with the behavior of liquid isolators in a pre-breakdown state. Two all-atom models and a united-atom model are used. Shear viscosity is calculated using the Green-Kubo formula. The force fields are compared with each other using the following criteria: the required time for one molecular dynamics step, the compliance of the main physical and transport properties with experimental values. The problem of the system equilibration is considered. The united-atom potential is used to model the n-triacontane liquid with an initial directional orientation. The time of relaxation to the disordered state, when all molecules orientations are randomized, are obtained. The influence of the molecules orientations on the shear viscosity value and the shear viscosity relaxation are treated.

Consideration is given to the filtration process of the two-phase multicomponent mixture in the porous. It is shown that "mixture-porous medium" system becomes self- oscillating one during filtration process under special conditions when there is a region of retrograde condensation on the phase diagram of the mixture. A mathematical model of the hydrocarbon mixtures filtration process of the methane series has been developed and a computer program for calculating hydrodynamic and thermodynamic characteristics of this process under isothermal conditions with phase transitions has been created. Consideration is given to the basic mechanisms influencing the filtration dynamics. Limits of the model applicability are discussed. Condition range for occurring self-oscillatory properties in "mixture-porous medium" system is determined by medium permeability, viscosity of the mixture, initial and boundary filtration conditions. Experimental filtration research of mixtures "methane-n-butane", "methane-propane-butane", "methane-pentane" under the thermodynamic conditions corresponding retrograde condensation region on the phase diagram have shown validity of this model. It is argued that any multicomponent mixture having a retrograde condensation region on the phase diagram appears as self-oscillating system under right conditions.

Some literature sources and web sites are analyzed in this report. These sources contain an information about thermophysical properties of H₂O including the vapor pressure P_s. (P_s,T)-data have a form of the international standard tables named as "IAPWS-IF97 data". Our analysis shows that traditional databases represent (P_s,T)-data at t > 0.002, here t = (T_c − T)/T_c is a reduced temperature. It is an interesting task to extrapolate IAPWS-IF97 data in to the critical region and to get (P_s,T)-data at t < 0.002. We have considered some equations P_s(t) and estimated that previous models do not follow to the degree laws of the scaling theory (ST). A combined model (CM) is chosen as a form, F(t,D,B), to express a function ln(P_s/P_c) in the critical region including t < 0.002, here D = (α, P_c,T_c,...) are critical characteristics, B are adjustable coefficients. CM has a combined structure with scaling and regular parts. The degree laws of ST are taken into account to elaborate F(t, D, B). Adjustable coefficients (B) are determined by fitting CM to input (P_s,T)-points those belong to IAPWS-IF97 data. Application results are got with a help of CM in the critical region including values of the first and the second derivatives for P_s(T). Some models P_s(T) are compared with CM.

The analysis of the response of dense plasma to electromagnetic waves of moderate intensity can be used as a tool to investigate the validity of the physical models describing the behavior of matter under extreme conditions. Within this work, the new experimental data on oblique incidence of polarized electromagnetic wave are presented. The plasma composition was calculated within a chemical picture and the integration of Maxwell equations to construct the spatial profile of the density of charge carriers of plasma was based on an interpolation formula for dc conductivity.

Experimental results for Brewster angle measurements are used to estimate the width of the shock front in xenon. The possible influence of the shock front width on the dense xenon reflectivity is discussed. The calculated values of the Brewster angle are shifted with respect to the experimental values. It may be partially related to the nonzero width of the wave front. The estimated values of the widths are 161, 154, and 145 nm for the wavelengths 1064, 694, and 532 nm respectively. These values are obtained within the framework of the Drude theory of reflection in the optically nonuniform media. The density functional theory (DFT) is applied to calculate values of the dielectric function and refraction. The effect is discussed if the widths found could influence the normal reflectivity obtained in the framework of the DFT.

The approach is developed to calculate reflectivity and high-frequency dielectric permeability of dense plasmas. The Kubo-Greenwood formula is applied. One-electron wave functions are used. Plane waves are substituted for the wave functions of the free states. Hydrogen-like wave functions are substituted for the wave functions of the bound states. The restriction of the excited pair bound states is included in the approach. Calculations are performed for the shock-compressed xenon. The results are in the fair agreement with the experimental data for densities ρ > 2 g/cm³ whereas the remarkable discrepancy appears at low densities. The discrepancy can be attributed to a finite width of the shock front. The width increases with the decrease of density and can contribute to the reflectivity at low densities.

The uniform electron gas (UEG) at finite temperature has recently attracted substantial interest due to the experimental progress in the field of warm dense matter. To explain the experimental data accurate theoretical models for high density plasmas are needed which crucially depend on treatment of quantum effects in electron-electron interaction as well as in the interaction of electrons with uniform positive background. To comply with these requirements we have developed the new quantum path integral model of the UEG and present the results of related direct path integral Monte-Carlo (DPIMC) simulations. Contrary to the known in literature approaches treating the electron-background interaction classically our simulations take into account the quantum effects in this interaction. We have observed very good agreement with known in literature results only up to moderate densities when the ratio of the average interparticle distance to the Bohr radius is of order four (r_s ≥ 4) and observe deviations for higher densities. At very high electron density (r_s ≈ 1) presented in literature approaches as well as our simulations are problematic due to the strong degeneracy of electrons and increasing fermion sign problem.

Thermodynamic properties of relativistic spinless particle described by the Klein–Gordon equation have been studied using the Newton–Wigner theory of particle in external potential field. Concept of Wiener path integral was extended on relativistic case. A new path integral Monte–Carlo method was developed for relativistic particle in external potential field. The bounds of applicability of available analytical approaches and related results have been specified by comparison with Monte–Carlo calculations. Developed path integral formalism can be directly extended on systems of many identical Newton–Wigner particles, which interact with external field and each other.

A new method for calculating the population of excited levels of helium atoms and ions is suggested. The method is based on direct solution of a system of balance equations for all energy levels for which it was possible to obtain process speed constants. The equations include terms for the processes of particle loss and income by excitation and deexcitation, ionization and recombination as well as losses due to diffusion and radiation. The challenge of solution of such large system is also discussed.

A model for the radio waves backscattering from both penetrable plasma and reflecting plasma is developed. The technique proposed is based on Huygens's principle and reduces the radar cross-section estimation to numerical integrations.

This paper presents the model variants of plasma layer creating by microwave discharges and plasma jet sources. Methods of creation a model quasi-dynamic plasma antenna on the basis of plasma jet and antenna type plasma structures of microwave range are also considered. Pulsed discharge in a capillary with ablative wall can be used as a method of creating plasma antenna. A microwave discharge is another perspective method for plasma antennas creation in centimeter-decimeter wavelengths range that allows us to apply this approach for modeling different types of plasma antennas (dipole, traveling wave antenna, spiral antenna, and others). Numerical modeling was initiated to analyze the interaction of microwave radiation with plasma layer. It is assumed that 2D consideration will allow investigating the influence of various types of regular spatial plasma structures on the characteristics of the transmission and scattering of EM waves beams. The model allows investigating also the development of MW plasma structures (it is virtually impossible to implement in the framework of 3D modeling).

The numerical technique was developed to solve heat and mass transfer problem in 3D hypersonic flow taking into account destruction of thermal protection system. Described technique was applied for calculation of heat and mass transfer in sphere-cone shaped body. The data on temperature, heat flux and mass flux were obtained.

The specific features of numerical method for gas dynamics problems are considered in this paper. The viscous flows are considered in a wide range of Mach number. The numerical method is based on conservation laws applied on unstructured heterogeneous mesh with further integration on complex cluster architectures. Application of unstructured mesh allows one to perform calculation of geometrically complex 3D objects with strict conservation properties. The developed numerical method includes multiple flux solvers (Godunov's, HLLC, Roe-Fix, AUSM, etc), first and second order spatial approximation, and explicit, semi-implicit or implicit first order time schemes. The method utilizes heterogeneous GPU HPC clusters. A wide range of problems is used for verification of the developed computational complex. All results on these problems had a good agreement with reference data.

Theory and numerical simulations of degradation spectra of electrons in gases are presented. Theory is based on the power spectra of degradation charged particles as the spectra with fluxes in energy space. Numerical calculations of the electron energy distribution function have been performed for ionospheric gas mixtures constituted of molecules N₂, O₂ and atom O under influence of high energy electron source with detailed elementary electron collision processes with molecules and atoms being taken into consideration. The energy expenses of electrons into ionization, dissociation and excitation of various levels have been obtained so that to determine the rates of electron collision processes. The dependence of the electron energy expenses into various inelastic electronic processes upon the energy of primary electron source has been revealed. The results are presented for the rates of numerous elementary processes of electron interaction with basic ionospheric components to be suitably determined.

The hypothesis of antigravitational interaction of elementary particles and antiparticles is applied to the simple two-component hydrodynamic model Λ-CDM (Lambda cold-dark matter) with gravitational repulsion and attraction. An increase in the Jeans instability rate, the presence of antiscreening, and the dominant role of the gravitational repulsion as a possible mechanism of spatial separation of matter and antimatter in the Universe are shown, as well as the observable acceleration of far galaxies. The sound wave is found for the two-component gravitational-antigravitational system. The suggested approach permits to reestablish the idea about baryon symmetry of the Universe, causing its steady large-scale flatness and accelerated Universe expansion.

A sole proton energy loss processes in an electron gas and the dependence of these processes on temperature and magnetic field are studied using molecular dynamics techniques in present work. It appears that for electron temperatures less than 100 K many body collisions affect the proton energy loss and these collisions must be taken into account. The influence of a strong magnetic field on the relaxation processes is also considered in this work. Calculations were performed for electron densities 10 cm^-3, magnetic field 1-3 Tesla, electron temperatures 10-50 K, initial proton energies 100-10000 K.

In this work, we discuss two-photon excitation and diagnostic of ultracold Rydberg atoms in a magneto-optical trap. Lithium atoms were excited by using ultraviolet cw laser. For identification of Rydberg transitions, we recorded resonance fluorescence of ultracold atoms. Spectra of transitions 2P-nS, 2p-nD were measured. Our results are in good agreement with calculations and experimental data available in literature. Presented work is a part of our project focused on preparation and study of Rydberg matter and ultracold plasma.

Earlier a two-component pseudopotential plasma model, which we called a "shelf Coulomb" model has been developed. A Monte-Carlo study of canonical NVT ensemble with periodic boundary conditions has been undertaken to calculate equations of state, pair distribution functions, internal energies and other thermodynamics properties of the model. In present work, an attempt is made to apply so-called hybrid Gibbs statistical ensemble Monte-Carlo technique to this model. First simulation results data show qualitatively similar results for critical point region for both methods. Gibbs ensemble technique let us to estimate the melting curve position and a triple point of the model (in reduced temperature and specific volume coordinates): T* ≈ 0.0476, v* ≈ 6 × 10^-4.

This paper is devoted to a careful study of two charge interaction in an equilibrium plasma within the Debye approximation. The effect of external boundary conditions for the electric field strength and potential on the electrostatic force is studied. The problem is solved by the method of potential decomposition into Legendre polynomials up to the fifth multipole term included. It is shown that the effect of attraction of identically charged macroparticles is explained by the influence of the external boundary. When the size of a calculation cell is increased the attraction effect disappears and the electrostatic force is well described by the screened Debye-Hückel potential.

In the present paper the dust particle charging is studied in a dry air plasma created by an external ionization source. The ionization rate is changed in the range 10¹-10²⁰ cm^-3s^-1. It is found that the main positive ion of the plasma is O⁺₄ and the main negative ones are O⁻₂ and O⁻₄. The point sink model based on the diffusion-drift approach shows that the screening potential distribution around a dust particle is a superposition of four Debye-like exponentials with four different spatial scales. The first scale almost coincides with the Debye radius. The second one is the distance, passed by positive and negative plasma components due to ambipolar diffusion in their recombination time. The third one is defined by the negative ion conversion and diffusion. The fourth scale is described by the electron attachment, recombination and diffusion at low gas ionization rates and by the recombination and diffusion of negative diatomic ions at high ionization rates. It is also shown that the electron flux defines the microparticle charge at high ionization rates, whereas the electron number density is much less than the ion one.

The current-pressure (I-P) characteristics of axially symmetric dc discharge of planar magnetron sputter were studied. The characteristics in argon and krypton gases for copper and aluminum cathodes and the spatial distributions of the plasma glow at different pressures are obtained. The sequence of local maximum and minimum is observed on current- pressure characteristics under defined conditions. The necessity of taking into account the gas heating by sputtered atoms for explaining the observed features of I-P characteristics is shown. Numerical simulation has allowed explaining the observed significant difference between the values of the discharge current density in argon and krypton.

Homogeneous incorporation of a small amount of binding material or modifying agent in the batch consisting of micron size particles is a problem of a composite material production process. In this work the problem is solved by deposition of a thin coating consisting of binding material on the initial powder particles by means of high-rate magnetron sputtering. The confinement of dusty particles in plasma was used in fine powder processing procedure. Composite powders based on the Al-Cu-Fe quasicrystalline particles with nickel coating were obtained. Their investigation showed that the method provides uniform incorporation of small quantities of additives (at concentration of about 3 wt. %) to fine powders. The powders were pressed at room temperature under quasi-hydrostatic conditions at high pressures. After pressing the samples were sintered in hydrogen at normal pressure. Structure and mechanical properties of the sintered samples were studied. The conditions of sintering the composite powder, which provide producing compacts with improved performance data, were established.

In this work the method of a single particle charge and mass measurement in electrodynamic Paul trap is proposed. In the experiments polydisperse Al₂O₃ particles were used. The measured masses were in the range from 1 × 10^-8 to 9 × 10^-8 g. The measured charges were in the range from 2 × 10⁵ to 1.3 × 10⁶ e.

The paper presents the numerical studies of effective forces acting on a charged microparticle inside the linear Paul trap in gas media. The locations of the microparticle trapping as the dependence on microparticle and trap parameters have been studied.

In this paper, we present the experimental results demonstrating the charged microparticles confinement in an electrodynamic trap in a gas flow and prove the selective possibility of these traps to capture charged microparticles in gas flows in a wide range of microparticle and trap parameters.

The influence of dust particles on the concentration of metastable neon atoms and ionization was investigated using the developed drift/diffusion model for plasma of positive column of glow discharge. The detailed de-excitation in neon was considered. In addition to usual plasma losses in dusty plasmas, the quenching of metastable atoms on dust particle surface was considered. The strong influence of dust particles on the ionization rate and concentration of metastable neon atoms in a positive column of glow discharge is shown to result from the change in the longitudinal electric field strength.

The formation of cryogenic colloid of charged particles in static magnetic traps was studied for the first time. We presented experimental results of formation of strongly correlated structures consisting of about 10³ particles. Ordered structures were formed by particles with a diameter of 30-60 microns with a charge up to 10⁷e. Estimates of mean interparticle distance, dust particle charges, coupling parameter and Lindemann parameter, which turned out to be typical for strongly coupled crystalline or glass-like systems.

In this work, the cryogenic dusty plasma, which is represented by a mixture of two dust components with different structural and dynamical properties, was experimentally investigated. Experiments were conducted in dc glow discharge at temperatures 10 and 77 K using CeO₂ micron powder as a dust. In dust structures obtained one of the components consists of dust particles with chain-like ordering (dust chains) and another component consists of fast- moving particles orbiting horizontally through the first component ("crazy" particles). Dust particle velocity distribution functions were obtained. The possible reasons of two-component dust structure formation were discussed.

In present work, the results of the numerical simulation of the dynamics of twodimensional clusters of 7 and 18 particles interacting via the Yukawa potential are presented. The simulation was carried out by the Langevin molecular dynamics method. We have numerically obtained the MFPT entropy functions for the systems of 7 and 18 particles for the various values of kinetic temperature, corresponding to the conditions of the laboratory experiments with gas-discharge dusty plasma. Three phase states of the considered small systems are registered: crystal, liquid and transitional. The mechanism of phase transitions in the systems under study is described. The suggested technique of the analysis of the system dynamics can be applied to the structures as small as desired.

We present the results of an experimental study of many-body correlations (three- and four-) of three-dimensional dust formations, confined in the plasma of high-frequency capacitive discharge. The analysis of dusty plasma system, based on the reconstruction of three coordinates of dust particles using the method of binocular observation, has been made for the first time. The obtained experimental results are compared with the superposition approximation.

Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.

One of the mechanisms of energy transfer between degrees of freedom of dusty plasma system can be described by equations similar to Mathieu equation with account of stochastic forces. Such equation is studied by analytical approach. The solutions for higher order of accuracy are obtained. The method for numerical solution and resonance zone detection is proposed. The solution for the extended Mathieu equation is obtained for wide range of parameter values. The results of numerical solution are compared with analytical solutions of different order and known analytical results for Mathieu equation.

One of the main problems of future missions to the Moon is associated with lunar dust. Solar wind flux and ultraviolet radiation interact with the lunar surface. As a result, there is a substantial surface change and a near-surface plasma sheath. Dust particles from the lunar regolith, which turned in this plasma because of any mechanical processes, can levitate above the surface, forming dust clouds. In preparing of the space experiments "Luna-Glob" and "Luna-Resource" particle-in-cell calculations of the near-surface plasma sheath parameters are carried out. Here we present some new results of particle-in-cell simulation of the plasma sheath formed near the surface of the moon as a result of interaction of the solar wind and ultraviolet radiation with the lunar surface. The conditions of charging and stable levitation of dust particles in plasma above the lunar surface are also considered.

Dynamical properties of particles in the chain-like and layered structures are studied with the help of Langevin MD approach. We considered infinite, confined chain-like structures, and extended layered structures with vertical (chain-like) and hexagonal ordering of particles in adjacent layers over a wide range of parameters, corresponding to the experimental conditions in the laboratory dusty plasmas. The nonreciprocal anisotropic interparticle interaction leads to a growth of kinetic energy of stochastic motion of particles especially its vertical component. Efficacy of the heating depends on the thermal particle motion, the anisotropy of the considered interparticle interaction and with decreasing the friction coefficient.

Two simplified variants of a dusty, condensed dispersed phase and colloid plasmas models are considered as a thermodynamically equilibrium combination of classical Coulomb particles: a 2-component electroneutral system of macro- and micro-ions (+Z, – 1) and a 3-component electroneutral mixture of macro-ions and two kinds of micro-ions (+Z, –1, +1). The base for a consideration is a phase diagram of dusty plasma by Hamaguchi et al (1997 Phys. Rev. E 56 4671) for an equilibrium charged system with the Yukawa potential. Parameters of a splitting the one-dimensional melting boundaries of the Hamaguchi diagram (i.e. hypothetical melting density gap between separate freezing liquid line (liquidus) and melting crystal line (solidus)) are discussed. Estimation of a density gap value is made. Additional splitting of all phase boundaries in the three-component model because of so-called non-congruency of all phase transitions in this model is discussed also.

Spectral measurements of Doppler profiles of the hydrogen H_α spectral line in a glow direct current discharge in a mixture of 1% hydrogen in argon at pressures of 60, 120 and 180 Pa were performed. Solid and mesh cathodes were used. It is brought out that the line shapes are Gaussian with the width corresponding to the effective temperature of the excited atoms of 35-60 eV for emission from the cathode region. The line width does not change with the pressure and the distance from cathode in the region of negative glowing and increases slightly with the distance from the mesh cathode outside of the discharge gap.

The nonlinear diffusion of a magnetic field and the large-scale instabilities arising upon an electrical explosion of conductors in a superstrong (2-3 MG) magnetic field were investigated experimentally on the MIG high-current generator (up to 2.5 peak current, 100 ns current rise time). It was observed that in the nonlinear stage of the process, the wavelength of thermal instabilities (striations) increased with a rate of 1.5-3 km/s.

The paper reports on an experimental study of the X-pinch soft x-ray source dynamics at a subnanosecond time resolution with the use of an x-ray imaging technique based on an AXIS-NX streak camera. The study was performed on a compact generator with a current amplitude of 300 kA to a short-circuit load and current rise time of 180 ns. It is shown that in the spectral range 1-1.55 keV, the X-pinch soft x-ray source in whole represents a set of sources which can be radially offset by ∼ 10 microns about the X-pinch axis. Each of the sources generates a pulse of duration 0.2-0.7 ns. The interval between the formation of the sources and hence between their radiation pulses is 0.5 ns and longer.

Soft x-ray emission from CuXX L-shell lines emitted by a dense X-pinch plasma have been investigated with high-resolution curved Bragg crystals at different angles of orientation. Single shot time integrated spectra show clear evidences of polarization for the Ne-like spectral lines 2s²2p^{6 1}S₀ → 2s²2p⁵3s¹P₁ (λ = 12.570 Å), 2s²2p^{6 1}S₀ → 2s²2p⁵3s³P₁ (λ = 12.8277 Å). The variation of the intensity ratio of these two well-separated L-shell lines is discussed in view of its application for suprathermal electron characterization under real experimental conditions of pinch plasmas. We demonstrated that the simultaneous use of two different polarization spectrometers (means 4 Bragg crystals) permitted a high level of confidence for the analysis of the variation of the line ratios due to polarization.

The formation of the strata during fast explosion of metal foils at current densities of 0.1 GA/cm² has been studied experimentally. To observe the strata, the soft x-ray radiation generated by an X-pinch was used. The study of the process of stratification during the foil explosion was carried out with a setup consisting of three generators. One of the generators (WEG-2), was operated to initiate the explosion of the foils, while the others (XPG radiographs) were used for diagnostics. The generator WEG-2 has the capacitance of 250 nF, the charge voltage of 20 kV, and the current rate of 16 A/ns. The radiographs XPG have the capacitance of 1 μF, the charge voltage of 43 kV, the current of 300 kA, and the current rise time of 180 ns. X-pinch produced by four Mo wires was a load for the radiographs. The delay between the operation of the WEG-2 and XPG generators was set using a DPG trigger pulse generator. We performed the experiments with the Al and Cu foils. The length of foil was 2 cm, the foil width was 1 mm, and the foil thickness was 6 μm. It has been revealed that strata were formed early in the explosion, i.e. at the stage when the metal melted. Analysis of the experimental results suggests that the most probable reason for the stratification is the thermal instability developing because of the increase in resistivity of the foil metal with temperature.

We study the evolution of tube material during the power current pulse is passing. Modelling this process, we need the time dependence of current, restored according to the time dependence of the electric field intensity, measured at the inner tube surface. For this purpose, the inverse problem was solved; the data obtained were used in the MHD-simulation.

Magnetically driven plasma implosion is studied numerically with the use of a 3D radiative MHD model. We consider a Z-pinch formed by an array of thin tungsten wires. In our calculations we take into account a time-extended plasma production due to a material evaporation by an individual wire caused by the heating electric current. Using a detailed model of the pinch kernel, a soft x-ray radiation intensity is analyzed numerically with resolution of temporal, spatial, angular and spectral radiation characteristics. The results are represented for the conditions pertinent to experiments with cylindrical tungsten wire arrays at Angara-5-1 facility (TRINITI, RF).

Research results for discharge initiated by wire explosion in hydrogen at initial pressures up to 30 MPa and current amplitudes up to 1 MA are presented. Measurements of channel radius oscillation amplitude by magnetic probe diagnostics were made to calculate channel plasma parameters. The amplitude of channel radius oscillations was observed to decrease with growth of initial gas pressure and to increase with growth of current amplitude.

The paper describes investigations of formation of high current electrical discharges emerging under free surface of liquid metal in tasks of melting and mixing intensification with use of electrovortex flow control. Discharge electrical characteristics, parameters of its ignition, visualization pictures of free surface deformation are presented here. Mechanisms of formation of the discharge over the liquid metal are discussed.

Experimental results of laboratory investigation of nonlinear processes in moist soil near electrode simulating grounding of electric power facilities are presented. A method of optical recording of spark formation in the soil is developed. Investigations were carried out at voltage of 20-50 kV and current pulse duration of tens of microseconds. The critical electric field and delay of sparks beginning in soil in depending on the electrode construction, moisture and impulse duration are obtained. The images of sparks in soil are obtained for the first time.

Laboratory experiments on both metal and dielectric polarized solid particle levitation between plane electrodes at static electric field are performed. The dependence of particles charge on their mass is studied. The particle charge is found to increase with particle mass. The method to obtain extremely high electric charge on particles at atmospheric pressure is introduced. The maximum electric charge 2.8 × 10⁷e is achieved in experiments with heavy metal particles.

In this paper, we review a multiple-wavepacket version of the Antisymmetrized Wave Packet Molecular Dynamics (AWPMD), that may be utilized to increase the accuracy and the performance of this quantum simulation method. The original WPMD method is based on parameterization of the electron wave function by a single Gaussian wave packet. It gives qualitatively better results than the classical Molecular Dynamics but the quantitative description of essentially quantum systems is rather poor. In this work, we describe a new technique based on multiple Gaussian expansion of the single-electron wave function, which is called Split Wave Packet Molecular Dynamics (SWPMD). The related theoretical formalism is given, followed by the analysis of static and dynamical properties of a quantum system of several particles, where the simulation results may be compared to the theoretical predictions. The tests are based on ionization of hydrogen atom under a strong laser pulse. We demonstrate that the SWPMD method may significantly improve the accuracy of the model wave function and enables one to simulate the quantum branching processes, including the tunneling, which was impossible in the single-wavepacket version of the method.

Pressure of plasma is calculated by using classical molecular dynamics method. The formula based on virial theorem was used. Spectrum pressure's fluctuations of singly ionized non-ideal plasma are studied. 1/f-like spectrum behavior is observed. In other words, flicker noise is observed in fluctuations of pressure equilibrium non-ideal plasma. Relations between the obtained result and pressure fluctuations within the Gibbs and Einstein approaches are discussed. Special attention is paid to features of calculating the pressure in strongly coupled systems.

A research of the diffusion of an ion in a liquid is carried out. Dependences of the diffusion coefficient on the ion-molecule potential, ion mass, liquid temperature and density are defined. The results are related to the ion solvation. The classical molecular dynamics method is applied. The effect of the ion solvation is discovered. Firstly, ion mass has no influence on the diffusion coefficient. This is because the total mass of the cluster formed by the ion and the ion solvation shell varies slightly while the mass of the ion changes significantly. In addition, the dependence on short-range interaction is found to be rather weak. The dependence of the diffusion coefficient on long-range interaction is found to be really stronger than on short- range. The ion velocity autocorrelation function calculated reveals a strong oscillatory character superimposed on the conventional functional liquid-type form. It reflects the oscillations of the ion inside the solvation shell. The relation between the ion mobility and temperature is found to be of the Arrhenius-type form.

It was examined the effect of electrode material on the value of specific thrust of the synthetic jets produced by symmetric actuator. The dependences of specific thrust on the distance between external electrodes for copper, aluminium, nickel and titanium was made. A considerable effect of the shape of the external electrodes on the electric field and current density in the tape drive and the specific thrust of the synthetic jet were investigated. The role of autoelectronic emission on the current in streamers and the value of volume force acting on the stream were also evaluated.

Evolution of the spark channel created by the high voltage pulse generator in 15% isopropyl alcohol solution in tap water was investigated experimentally. Fast camera images show the start of spark discharge channel with the anode region glowing, which is due to ionization-overheating instability near the surface of anode electrode. Measured propagation velocity is about 4 m/s and points to thermal process of channel evolution. Partial discharges in gas bubbles near the spark channel were observed. When the channel bridges the gap the cathode flash of lightning occurs which is much brighter than anode glowing and channel one. After destruction of the spark channel the cathode glowing stays for a longer period than anode one.

A numerical simulation was performed to study the formation of a runaway electron (RAE) beam from an individual emission zone in atmospheric pressure air discharges with a highly overvolted interelectrode gap. It is shown that the formation of a RAE beam in discharges at high overvoltages is much contributed by avalanche processes.

An analytical model and the results of modeling are presented for movement of electrons in recombining hydrogen plasma. It is shown that in case of taking into account the magnetic moment and angular momentum as well as spin flip of electron in magnetic field the electron comes to the orbit with angular momentum ħ/2. If azimuthal and radial components of kinetic energy of electron are equal then the full energy of such the orbits is 13.6 eV.

Axial plasma jets at the final stage of plasma focus discharge filled by neon or argon were studied by the method of shearing interferometry. It was found that neon plasma is more stable than argon one and jets in neon are stronger than in argon. The velocity of current sheath, taken from experiment, is V_sh = (2-3) × 10⁶ cm/s, while the velocity of cumulative jet is Vj = (3-4) × 10⁷ cm/s. These features are supported by theoretical interpretation given in the frame of 2D MHD model.

A method to synthesize graphene-like materials using dc high current divergent anode-channel plasma torch has been developed. Carbon atoms are generated by decomposition of propane-butane and methane in a thermal plasma jet. Products of synthesis are characterized by electron microscopy, thermogravimetry, Raman spectroscopy and porosimetry. Effect of experimental conditions on the morphology, phase composition and porosity of the products of synthesis are investigated. The optimal conditions have been found.

Plasma sources of model substances are necessary to solve problems associated with development of the spent nuclear fuel (SNF) plasma separation method. Lead was chosen to simulate kinetic and dynamic properties of the heavy SNF components. In this paper we present the results of a study of a lead vapor discharge with a lead concentration of 10¹²-10¹³ cm^-3. Ionization was carried out by an electron beam (with energy of up to 500 eV per electron) inside a centimeter gap between planar electrodes. The discharge was numerically modeled using the hydrodynamic and single-particle approximation. Current-voltage characteristics and single ionization efficiency were obtained as functions of the vapors concentration and thermoelectric current. An ion current of hundreds of microamperes at the ionization efficiency near tenths of a percent was experimentally obtained. These results are in good agreement with our model.

Questions of generation buffer magnetized plasma and creation of given profile of the electrostatic potential in the working volume of the separators chamber were investigated for the purposes of plasma separation spent nuclear fuel method. Experimental researches with reflective discharge in helium were carried out. Pressures were 1 and 35 mTorr, the magnetic field was up to 2.1 kG and voltages were up to 1.2 kV. Volt-current characteristics of the discharge and the potential distribution profile, obtained using the isolated probe, were measured. Helicon discharge was chosen as a source of buffer plasma. For a discharge antenna characteristics required for generating buffer plasma in a volume of 2 m³ were calculated.

Experimental study of vacuum arc with distributed spot on plumbum cathode at temperatures 1.25-1.45 kK has been presented. At these conditions current density of thermionic emission from cathode was less than 1 μA/cm², while the mean current density on the cathode was about 10 A/cm². Plumbum was placed in heat-insulated crucible (cathode) with external diameter 25 mm. Electron-beam heater was situated under the crucible. Arc current was changed in the range 20-70 A, arc voltage was about 15 V. The studied arc is characterized by the absence of the random voltage fluctuations; the micro particles of cathode erosion products were observed only in transition regimes. Spectral data of plasma radiation and values of the heat flow from plasma to cathode were obtained. It has been experimentally established that the evaporation rate in arc approximately two times less than without discharge. The average charge of plumbum particles in the cathode jet was in range 0.2-0.3e. Comparison of the characteristics of studied discharge on thermionic gadolinium cathode and non-thermionic cathodes was fulfilled. One can assume that ions provide the charge transfer on the cathode in the studied discharge.

During study of vacuum discharge in plumbum evaporating from molybdenum crucible in identical geometry of discharge gap and the same crucible temperature existence of two different discharge forms were observed. These two forms are vacuum arc with current above 10 A and voltage about 15 V and high-voltage discharge with current about 10 mA and voltage of 340 V. Plumbum was placed in heat-isolated crucible (cathode). Electron-beam heater was situated under the crucible. At the temperature of 1.25 kK that corresponds to plumbum saturated vapor pressure about 0.1 kPa voltage from power source (380 V, 200 A) was applied to anode and high-voltage discharge initiated with characteristics mentioned above. After a few seconds this discharge could turn into arc or could exist hundreds of seconds until total plumbum evaporation. Glow of discharge could take the form of a cone, harness or plasma bunch that hanged at the appreciable distance from the electrodes. The estimations of plasma parameters are presented.

Megawatt generator of high-enthalpy air plasma jet (H ≥ 30 kJ/g) is constructed. Plasmatron belongs to the class of plasma torches with thermionic cathode, tangential swirl flow and divergent channel of an output electrode-anode. Plasma torch ensures the formation of the slightly divergent (2α = 12°) air plasma jet with the diameter D = 50 mm. The current-voltage characteristics of the plasma torch has virtually unchanged voltage relative to its current with enhanced (compared with arcs in cylindrical channels) stable combustion zone. Preliminary analysis of the obtained air plasma spectra shows that at a current of 1500 A near-axis zone of the plasma jet is characterized by a temperature of up to 15000 K, and the peripheral radiating area has a temperature of 8000-9000 K.