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Karpov S.A.,Dukhov All Russia Research Institute of Automatics | Potapenko I.F.,RAS Keldysh Institute of Applied Mathematics
Plasma Physics Reports | Year: 2015

A stochastic method of simulation of Coulomb interaction is considered. The main idea of the method is to approximate the nonlinear Landau kinetic collision integral by the Boltzmann integral. In its realization, the method can be attributed to a wide class of Monte Carlo-type methods. It is easily combined with the existing particle methods used to simulate collisionless plasmas. This is important for simulation of the dynamics of both laboratory and space plasmas when the mean free path of plasma particles is comparable with the plasma inhomogeneity scale length. Illustrative examples of relaxation of two-temperature plasma being subject to a high-frequency alternating electric field are given, and differences from their classical description are considered. The method satisfies the conservation laws for the number of particles, momentum, and energy and is simple and efficient in implementation. © 2015, Pleiades Publishing, Ltd. Source

Ashitkov S.I.,RAS Joint Institute for High Temperatures | Komarov P.S.,RAS Joint Institute for High Temperatures | Ovchinnikov A.V.,RAS Joint Institute for High Temperatures | Struleva E.V.,RAS Joint Institute for High Temperatures | And 3 more authors.
Quantum Electronics | Year: 2014

Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ∼109 s-1. © 2014 Kvantovaya Elektronika and Turpion Ltd. Source

Bork L.V.,Institute of Theoretical and Experimental Physics | Ogarkov S.L.,Dukhov All Russia Research Institute of Automatics
Theoretical and Mathematical Physics | Year: 2014

We study the problem of the condensate (stochastic average) origination for an auxiliary field in the Kardar-Parisi-Zhang equation and its matrix generalization. We cannot reliably conclude that there is a condensate for the Kardar-Parisi-Zhang equation in the framework of the one-loop approximation improved by the renormalization group method. The matrix generalization of the Kardar-Parisi-Zhang equation permits a positive answer to the question of whether there is a nonzero condensate, and the problem can be solved exactly in the large-N limit. © 2014 Pleiades Publishing, Ltd. Source

Kosov M.V.,Dukhov All Russia Research Institute of Automatics | Chertkov A.V.,Skolkovo Institute of Science and Technology
Instruments and Experimental Techniques | Year: 2015

A numerical analysis of the confidence of detecting a significant deviation from the background distribution according to the Neumann-Pirson for random quantities, which obey the Poisson criterion, was performed. Relationships are established between such quantities as the signal-to-background ratio, the expected mean background value, the detection threshold, and the detection confidence. To completely define the problem, it is sufficient to know two of these four parameters. Because the distribution of events in each bin of a histogram at unit weights of events obey the Poisson distribution law, the obtained mutual dependences of variables are of fundamental importance and can be used in searches for a deviation from predictions of standard models or for a desired-signal detection against a background of known background distributions. The determined confidence values comply with the values that were obtained using the χ2 method (Pirson criterion). © 2015, Pleiades Publishing, Inc. Source

Inogamov N.A.,Russian Academy of Sciences | Zhakhovskii V.V.,Dukhov All Russia Research Institute of Automatics | Khokhlov V.A.,Russian Academy of Sciences
Journal of Experimental and Theoretical Physics | Year: 2015

It is well known that during ablation by an ultrashort laser pulse, the main contribution to ablation of the substance is determined not by evaporation, but by the thermomechanical spallation of the substance. For identical metals and pulse parameters, the type of spallation is determined by film thickness df. An important gauge is metal heating depth dT at the two-temperature stage, at which electron temperature is higher than ion temperature. We compare cases with df < dT (thin film) and df ≫ dT (bulk target). Radius RL of the spot of heating by an optical laser is the next (after df) important geometrical parameter. The morphology of film bulging in cases where df < dT on the substrate (blistering) changes upon a change in radius RL in the range from diffraction limit RL ∼ λ to high values of RL ≫ λ, where λ ∼ 1 μm is the wavelength of optical laser radiation. When df < dT, RL ∼ λ, and Fabs > Fm, gold film deposited on the glass target acquires a cupola-shaped blister with a miniature frozen nanojet in the form of a tip on the circular top of the cupola (Fabs and Fm are the absorbed energy and the melting threshold of the film per unit surface area of the film). A new physical mechanism leading to the formation of the nanojet is proposed. © 2015, Pleiades Publishing, Inc. Source

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