arXiv subjects

Konstantin V. Khishchenko

Publications and source records attributed to Konstantin V. Khishchenko.

7 recordsLinked to original sources

arXiv2020

High- and low-entropy layers in solids behind shock and ramp compression waves

Non-uniform temperature fields are analyzed, which arise in the problems of formation of the steady shock wave at impact and ramp loading of metals, exit of the steady shock wave to the free surface, and the shock wave passing through the interface between two different materials. Theoretical analysis and computations show that high-entropy (with the temperature increase) and low-entropy (with the temperature decrease) layers arise near the interfaces in the above problems of shock and ramp loading. The impact produces the high-entropy layer; while the ramp loading can result in the both high- and low-entropy layers. At the shock wave passing through the interface, the high-entropy layer is formed in the lower-impedance material and the low-entropy -- in the higher-impedance one. The formation of high-entropy layer at impact is supported by molecular-dynamics simulations in addition to continuum modeling. The high- and low-entropy layers should be taken into account in simulations of shock-wave processes in thin targets or in other cases where surface effects are important.

physics.flu-dyn↗

arXiv2016

Study of extreme states of matter at high energy densities and high strain rates with powerful lasers

In the paper, a review of most important results of experimental studies of thermonuclear plasma in conical targets, generation of shock waves and spallation phenomena in different materials, which were carried out at laser facilities of the A M Prokhorov General Physics Institute RAS since 1977, is presented.

physics.plasm-ph↗

arXiv2015

Comparison of Hugoniots calculated for aluminum in the framework of three quantum-statistical models

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 $10^7$ GPa. Calculated Hugoniots are compared with available experimental data.

physics.plasm-ph↗

arXiv2015

Equation of state for tungsten over a wide range of densities and internal energies

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.

cond-mat.mtrl-sci↗

arXiv2014

Implementation of kinetics of phase transitions into hydrocode for simulation of laser ablation

We model an interaction of femtosecond laser pulses (800 nm, 100 fs, 1-100 TW/cm$^2$) with metal targets (Al, Au, Cu, and Ni). A detailed analysis of laser-induced phase transitions, melting wave propagation and material decomposition is performed using a thermodynamically complete two-temperature equation of state with stable and metastable phases. Material evaporation from the surface of the target and fast melting wave propagation into the bulk are observed. On rarefaction, the liquid phase becomes metastable and its lifetime is estimated using the theory of homogeneous nucleation. Mechanical fragmentation of the target material at high strain rates is also possible because of void growth and confluence. In our simulation several ablation mechanisms are observed but the major output of the material is found to originate from the metastable liquid state. It can be decomposed either into a liquid-gas mixture near the critical point, or into droplets at high strain rates and negative pressure. The simulation results correlate with available experiments.

physics.comp-ph↗

arXiv2014

Plane thermonuclear detonation waves initiated by proton beams and quasi-one-dimensional model of fast ignition

The one-dimensional (1D) problem on bilatiral irradiation by proton beams of the plane layer of condensed DT mixture with length $2H$ and density $ρ_0 \leqslant 100ρ_s$, where $ρ_s$ is the fuel solid-state density at atmospheric pressure and temperature of 4 K, is considered. The proton kinetic energy is 1 MeV, the beam intensity is $10^{19}$ W/cm$^2$ and duration is 50 ps. A mathematical model is based on the one-fluid two-temperature hydrodynamics with a wide-range equation of state of the fuel, electron and ion heat conduction, DT fusion reaction kinetics, self-radiation of plasma and plasma heating by alpha-particles. If the ignition occurs, a plane detonation wave, which is adjacent to the front of the rarefaction wave, appears. Upon reflection of this detonation wave from the symmetry plane, the flow with the linear velocity profile along the spatial variable $x$ and with a weak dependence of the thermodynamic functions of $x$ occurs. An appropriate solution of the equations of hydrodynamics is found analytically up to an arbitrary constant, which can be chosen so that the analytical solution describes with good accuracy the numerical one. The gain with respect to the energy of neutrons $G\approx 200$ at $Hρ_0 \approx 1$ g/cm$^2$, and $G>2000$ at $Hρ_0 \approx 5$ g/cm$^2$. To evaluate the ignition energy $E_{\mathrm{ig}}$ of cylindrical targets, the quasi-1D model, limiting trajectories of $α$-particles by a cylinder of a given radius, is suggested. The model reproduces the known theoretical dependence $E_{\mathrm{ig}} \sim ρ_0^{-2}$ and gives $E_{\mathrm{ig}} = 160$ kJ for $ρ_0 = 100ρ_s \approx 22$ g/cm$^3$.

physics.plasm-ph↗

arXiv2008

Modeling of optical, transport, and thermodynamic properties of Al metal irradiated by intense femtosecond laser pulses

A theoretical model is developed for the interaction of intense femtosecond laser pulses with solid targets on the basis of the two-temperature equation of state for an irradiated substance. It allows the description of the dynamics of the plasma formation and expansion. Comparison of available experimental data on the amplitude and phase of the complex reflection coefficient of aluminum with the simulation results provides new information on the transport coefficients and absorption capacity of the strongly coupled Al plasma over a wide range of temperatures and pressures.

physics.plasm-ph↗