News Article | November 14, 2016
Large-scale plasma simulation is an increasingly demanding area of computational physics with applications in a variety of research and industries. In particular, simulations of ultra-intense laser pulses interaction with various targets currently play a key role in discovering ways of using intense lasers for important applications ranging from creating compact ion sources for hadron therapy to fundamental experiments in quantum electrodynamics, as well as nuclear and quark-nuclear physics. A collaborative team created a Particle-in-Cell plasma simulation tool called PICADOR that is being used in this research. PICADOR is a tool for Particle-in-Cell plasma simulation on heterogeneous cluster systems. The core of the code is developed at Lobachevsky State University of Nizhni Novgorod (Russia) by an interdisciplinary team of researchers in physics, computer science and high performance computing (http://hpc-education.unn.ru/en/research/overview/laser-plasma). PICADOR is used and extended in collaboration with the Institute of Applied Physics of the Russian Academy of Sciences and Chalmers University of Technology (Sweden). “There is a growing need for carrying out large-scale 3D particle-in-cell simulations in several research directions of plasma physics,” says Dr. Iosif Meyerov, vice-head of mathematical software and supercomputing technologies department at Lobachevsky State University of Nizhni Novgorod, Russia. “Performing such simulations is possible on supercomputers with specialized parallel codes. The particle-in-cell method inherently allows massively parallel processing and thus can be efficiently implemented on supercomputers. The PICADOR code is an important tool in a multitude of research projects that can benefit from using the novel architecture of Intel systems.” “The growth of computational power accompanied with multilevel parallelization and optimization leads to gradual extension of capabilities of particle-in-cell codes, giving access to fascinating studies that have been previously impossible,” says Dr. Arkady Gonoskov, researcher, Lobachevsky State University of Nizhni Novgorod, Institute of Applied Physics of RAS, Chalmers University of Technology, who coordinates the PICADOR code development and use in research projects. PICADOR helps to discover new approaches to laser-drive ion acceleration Using intense lasers for accelerating ions during interaction with special targets is one of the most interesting applications of intense lasers that could have a high impact in industry, medicine and science. Although various approaches have been proposed, finding a way to accelerate ions to a sufficiently high energy remains one of the greatest challenge in this area for more than 15 years. Recently, simulations with PICADOR code helped theoreticians from Chalmers University of Technology (Sweden) Felix Mackenroth, Arkady Gonoskov and Mattias Marklund discover and propose a new basic approach that they called Chirped-Standing-Wave Acceleration . The distinguishing feature of the approach is a complete control of the acceleration process achieved via frequency variation within a laser pulse, so-called chirp. Simulations indicate the possibility of using currently available lasers for creating a source of protons with energy of 100 MeV, which is sufficient for many topical applications. Another interesting research activity performed based on simulations with PICADOR code is identifying how light of extraordinary intensity can produce avalanches of electron-positron pairs, creating a plasma, something which will be observable with the next generation of high intensity lasers facilities, such as XCELS [http://www.xcels.iapras.ru/]. According to Dr. Arkady Gonoskov, “The physics involved, as well as being computationally demanding, is extremely complex, which required developing a variety of sophisticated algorithms [A. Gonoskov et al. Phys. Rev. E 92, 023305 (2015)]. Simulations show that the collective dynamics of particles under these extreme conditions gives rise to a rich variety of unexpected phenomena, and yields new opportunities to increase our understanding of light, matter and the vacuum. For example, one expects particles to be pushed out of the regions of highest intensity, due to light pressure. However, as we recently discovered, the particles can behave counter-intuitively and be attracted to these regions of extreme intensity, because of so-called anomalous radiative trapping . As a result, an extremely dense bunch of particles forms and interact with the strong electromagnetic field of the laser, giving rise to a unique source of energetic particles and photons.”
Snetkov I.L.,RAS Institute of Applied Physics |
Yasuhara R.,Japan National Institute for Fusion Science |
Starobor A.V.,RAS Institute of Applied Physics |
Palashov O.V.,Lobachevsky State University of Nizhni Novgorod
Optics Express | Year: 2014
A Faraday isolator with compensation of thermally induced depolarization outside magnetic field was implemented for the first time on TGG ceramics. Stable isolation ratio of 38 dB in steady-state regime at a laser power of 300 W was demonstrated in experiment. Theoretical estimates show a feasibility of a device that would provide an isolation ratio higher than 30 dB up to laser power of 2kW. © 2014 Optical Society of America.
Zorine A.V.,Lobachevsky State University of Nizhni Novgorod
Queueing Systems | Year: 2014
A polling system with switchover times and state-dependent server routing is studied. Input flows are modulated by a random external environment. Input flows are ordinary Poisson flows in each state of the environment, with intensities determined by the environment state. Service and switchover durations have exponential laws of probability distribution. A continuous-time Markov chain is introduced to describe the dynamics of the server, the sizes of the queues and the states of the environment. By means of the iterative-dominating method a sufficient condition for ergodicity of the system is obtained for the continuous-time Markov chain. This condition also ensures the existence of a stationary probability distribution of the embedded Markov chain at instants of jumps. The customers sojourn cost during the period of unloading the stable queueing system is chosen as a performance metric. Numerical study in case of two input flows and a class of priority and threshold routing algorithms is conducted. It is demonstrated that in case of light inputs a priority routing rule doesn't seem to be quasi-optimal. © 2014 Springer Science+Business Media New York.
Erofeeva E.A.,Lobachevsky State University of Nizhni Novgorod
Dose-Response | Year: 2014
Chlorophyll and carotenoid content (ChCar), lipid peroxidation (LP) and growth parameters (GP) in plants are often used for environmental pollution estimation. However, the nonmonotonic dose-response dependences (hormesis and paradoxical effects) of these indices are insufficiently explored following exposure to different pollutants. In this experiment, we studied nonmonotonic changes in ChCar, LP, GP in wheat seedlings (Triticum aestivum L.) upon exposure to lead, cadmium, copper, manganese, formaldehyde, the herbicide glyphosate, and sodium chloride in a wide range from sublethal concentration to 102-105 times lower concentrations. 85.7% of dose-response dependences were nonmonotonic (of these, 5.5% were hormesis and paradoxical effects comprised 94.5%). Multiphasic dependences were the most widespread type of paradoxical effect. Hormesis was a part of some multiphasic responses (i.e. paradoxical effects), which indicates a relationship between these phenomena. Sublethal pollutant concentrations significantly increased LP (to 2.0-2.4 times, except for manganese and glyphosate) and decreased GP (to 2.1-36.6 times, except for glyphosate), while ChCar was reduced insignificantly, normalized or even increased. Lower pollutant concentrations caused a moderate deviation in all parameters from the control (not more than 62%) for hormesis and paradoxical effects. The seedling parameters could have different types of nonmonotonic responses upon exposure to the same pollutant. © 2014 University of Massachusetts.
Fedoseev V.B.,Lobachevsky State University of Nizhni Novgorod
Physics of the Solid State | Year: 2015
Conditions for the formation and existence of stable and metastable thermodynamic states in a system with phase transformations have been considered. As the system decreases to nano- and submicron sizes, the degeneracy of the phase diagram in stratified mixtures is removed, due to which images of phase equilibria in the diagram has variants that substantially differ from the diagram of a macroscopic system by critical stratification temperatures, composition of coexisting solutions, and region of existence of metastable phases. This size effect is considered using the example of phase transformations in the Bi-Sb solid solution. © 2015, Pleiades Publishing, Ltd.
Tokita M.,Lobachevsky State University of Nizhni Novgorod
Nanotechnologies in Russia | Year: 2015
This article describes recent trends in Spark Plasma Sintering (SPS) technology. The SPS method is widely recognized as a useful sintering technique to develop various kinds of attractive ceramics, metals, and composite materials due to its excellent features of rapid heating, electromagnetic field effect, and a well-controlled microstructure. © 2015, Pleiades Publishing, Ltd.
Dubkov A.,Lobachevsky State University of Nizhni Novgorod
Acta Physica Polonica B | Year: 2012
The stochastic Verhulst equation for the population density with fluctuating volume of resources is considered. Using the exact solution of this equation, the conditional probability density function is calculated for the excitation in the form of Lévy white noise with one-sided stable distribution. The phenomenon of transient bimodality and non-monotonic relaxation of mean population density for the white noise with Lévy-Smirnov stable distribution are found. An exact expression for the transitional time from bimodality to unimodality is obtained. It is interesting that for such a case the correlation function of population density in a steady state has a simple exponential form, and the correlation time does not depend on noise parameters.
Chernov A.V.,Lobachevsky State University of Nizhni Novgorod
Automation and Remote Control | Year: 2014
The paper is devoted to finding sufficient conditions for an ε-equilibrium in the sense of piecewise-program strategies in antagonistic games associated with nonlinear controlled functional operator equations and cost functionals of a rather general form. The concept of piecewise-program strategies is defined based on the concept of Volterra set chain for operators involved in equations controlled by opponent players. Reduction of distributed control systems to equations of this type is illustrated by examples. © 2014 Pleiades Publishing, Ltd.
Lobachevsky State University of Nizhni Novgorod | Date: 2012-07-11
The device comprises a ball and a panel that is made in the form of a periodic corrugation. The amplitude of the corrugation at least 10 times smaller than the period of corrugation, and the ball has a diameter which is at least 10 times smaller than the period of corrugation. Corrugations of the panel can be made sinusoidal, trapezoidal, triangular, or have other more complex forms. The device can be provided with a means for throwing the ball at different angles to the plane of the panel and at different initial velocities. The technical result obtained when using the claimed invention is a device that has broad potential as a visual aid in learning the peculiarities of motion of bodies under the action of external forces.
Lobachevsky State University of Nizhni Novgorod | Date: 2012-08-03
The invention relates to table or floor games based on throwing a ball into the game field, and can be used in organizing leisure and entertainment for both children and adults. The game comprises a game field with a plurality of holes and at least one movable trap for the ball outside the game field. The trap for the ball may be fixed to a rod, which is slidably mounted on a bar, said bar being attached to the sidewall, which limits the game field. The trap for the ball may be fixed to a rod, which is mounted on a movable platform.