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Kononenko T.V.,National Research Nuclear University | Dyachenko P.N.,Russian Academy of Sciences | Konov V.I.,National Research Nuclear University
Optics Letters | Year: 2014

2D photonic crystals formed inside monocrystalline diamond to operate in the IR spectral range are reported. The photonic structures consisting of 150-μm-long graphitized wires arranged in a square matrix with a period of 4 μm were produced by laser writing with ultrashort pulses. Transmittance spectra (γ = 1-14 μm) measured for the structures with increasing thickness demonstrate the occurrence of few minima being different for TM and TE polarization modes. Complex refraction index of the laser-modified material was evaluated for the first time in order to be used in computer simulation of the structures. © 2014 Optical Society of America.

Kalashnikov O.A.,National Research Nuclear University
Proceedings of the European Conference on Radiation and its Effects on Components and Systems, RADECS | Year: 2011

Analysis of total dose failure level variations of different manufacturer's integrated circuits is presented. More than double difference of failure levels within a lot and between lots proved to be rather typical. The variations distribution for different manufacturers is presented. © 2011 IEEE.

Lozovik Y.E.,Moscow Institute of Physics and Technology | Ogarkov S.L.,National Research Nuclear University | Sokolik A.A.,Russian Academy of Sciences
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Condensation of pairs formed by spatially separated electrons and holes in a system of two isolated graphene layers is studied beyond the mean-field approximation. Suppression of the screening of the pairing interaction at large distances, caused by the appearance of the gap, is considered self-consistently. A mutual positive feedback between the appearance of the gap and the enlargement of the interaction leads to a sharp transition to a correlated state with a greatly increased gap above some critical value of the coupling strength. At a coupling strength below the critical value, this correlation effect increases the gap approximately by a factor of 2. The maximal coupling strength achievable in experiments is close to the critical value. This indicates the importance of correlation effects in closely spaced graphene bilayers at weak substrate dielectric screening. Another effect beyond the mean-field approximation considered is the influence of vertex corrections on the pairing, which is shown to be very weak. © 2012 American Physical Society.

Ivanov Y.B.,National Research Nuclear University | Soldatov A.A.,National Research Nuclear University MEPhI
Physical Review C - Nuclear Physics | Year: 2015

Analysis of directed flow (v1) of protons, antiprotons, and pions in heavy-ion collisions is performed in the range of incident energies sNN=2.7-27 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS involving deconfinement transitions: a first-order phase transition and a smooth crossover transition. High sensitivity of the directed flow, especially the proton one, to the EoS is found. The crossover EoS is favored by the most part of considered experimental data. A strong wiggle in the excitation function of the proton v1 slope at the midrapidity obtained with the first-order-phase-transition EoS and a smooth proton v1 with positive midrapidity slope, within the hadronic EoS unambiguously disagree with the data. The pion and antiproton v1 also definitely testify in favor of the crossover EoS. The results obtained with deconfinement EoS's apparently indicate that these EoS's in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. © 2015 American Physical Society.

Ivanov Y.B.,National Research Nuclear University | Soldatov A.A.,National Research Nuclear University MEPhI
Physical Review C - Nuclear Physics | Year: 2015

The transverse-momentum-integrated elliptic flow of charged particles at midrapidity, v2(charged), and that of identified hadrons from Au+Au collisions are computed in a wide range of incident energies 2.7 ≤sNN≤39 GeV. The simulations are performed within a three-fluid model by employing three different equations of state (EoSs): a purely hadronic EoS and two versions of the EoS involving the deconfinement transition - a first-order phase transition and a smooth crossover one. The present simulations demonstrate low sensitivity of v2(charged) to the EoS. All considered scenarios equally well reproduce recent STAR data on v2(charged) for mid-central Au+Au collisions and properly describe its change of sign at the incident energy decrease below sNN≈3.5 GeV. The predicted integrated elliptic flow of various species exhibits a stronger dependence on the EoS. A noticeable sensitivity to the EoS is found for antibaryons and, to a lesser extent, for K- mesons. In particular, the v2 excitation functions of antibaryons exhibit a nonmonotonicity within the deconfinement scenarios that was predicted by Kolb, Sollfrank, and Heinz. However, low multiplicities of antibaryons at sNN≤10 GeV result in large fluctuations of their v2, which may wash out this nonmonotonicity. © 2015 American Physical Society.

Skorobogatov P.K.,National Research Nuclear University
Russian Microelectronics | Year: 2013

The adequacy of the laser simulation of volume ionization effects (dose rate) in microcircuits is violated due to the influence of surface metallization. It is shown that the optical diffraction of the laser emission restricts possible applications of this method by 0.18-μm design rules and higher. © 2013 Pleiades Publishing, Ltd.

Ivanov Y.B.,National Research Nuclear University
Journal of Physics: Conference Series | Year: 2016

It is argued that an irregularity in the baryon stopping is a natural consequence of onset of deconfinement occurring in the compression stage of a nuclear collision. It is an effect of the softest point inherent in an equation of state (EoS) with a deconfinement transition. In order to illustrate this effect, calculations within the three-fluid model were performed with three different EoS's: a purely hadronic EoS, an EoS with a first-order phase transition and that with a smooth crossover transition.

The results of experimental studies and simulations of transient radiation effects in microwave monolithic integrated circuits, based on heterostructure field-effect transistors, affected by the pulse ionizing radiation, are presented. The physical model, which adequately describes transient radiation effects in field-effect transistors in dose rate range up to 1012 rad/s, is proposed. Based on the physical model, the equivalent electric circuit, taking into account the dominating ionization effects, intended for using in the computer-aided design (CAD), is constructed. The simulated ionizing responses of the microwave low-noise amplifier (LNA) MIC are in accordance with the experimental data. © 2014 Pleiades Publishing, Ltd.

News Article | December 13, 2016
Site: www.cemag.us

National Research Nuclear University (MEPhI) scientists have figured out how the change of nanostructure of materials for energy reactors of the future will affect their plasticity, heat resistance, and other important properties. Currently, one of the most promising areas in nuclear power are the development of new fast reactors and the creation of a workable fusion reactor. The first will allow close the nuclear fuel cycle and make nuclear energy more environmentally friendly. If the second becomes possible, then in the future there will be a chance to produce energy in a brand new way. The most famous project is designed to bring the appearance of an energy fusion reactor — ITER (International Thermonuclear Experimental Reactor). One difficulty in creating new energy devices is that they all suggest the presence of extreme conditions of use in the energy zone. Therefore, the materials to be used in the active areas of new reactors must meet extremely high demands. Being exposed to high temperatures and the flow of high-energy radiation, modern materials are rapidly degraded. Most of them can withstand strong irradiation dose, at which each atom in the material moves 80 to 90 times. For the energy of thermonuclear installations this parameter should be twice as much. This resistance of the materials in the area of ​​use of energy determines the effectiveness and safety of a nuclear reactor. MEPhI scientists consider it possible to solve this problem with the help of nanotechnology. Ferritic-martensitic steels based on Fe-Cr alloys and dispersion-hardened steel oxides are considered to be promising for future power plants. In their works, scientists managed to experimentally demonstrate the mechanisms of atomic-scale restructuring of these materials, as well as to show how redistribution of atoms happens, resulting in a significant increase in their fragility and loss of plasticity. The results of these studies have been published in the Journal of Nuclear Materials and Journal of Nuclear Materials and Energy. It is known that the change of the nanostructure can fundamentally change the properties of the structural material. And, as a result, significantly reduce the time of operation of settings’ active zones, made of it. In some cases, scientists, on the contrary, succeed in picking up such nanostructured changes that significantly extend the capabilities of the products and provide them with unique properties, such as large heat resistance. In their experiments, experts influenced in a different way the model alloys Fe-Cr and steels, dispersion-reinforced by oxides, and then recorded arising changes in the properties of materials on the nanoscale, using the atomic-probe tomography. "In our studies, we have analyzed the state of nanoscale materials and adjustment under different impacts. We carried out the thermal aging, and then, using beams of metal ions, found that their effects might lead to the reducing of nanostructures," says Deputy Head of MEPhI department of physics of extreme states of matter of the Institute of nuclear physics and technologies Sergey Rogozhkin. According to Rogozhkin, research results can be used both when creating materials for ITER, and for the future energy systems. "The aim of the ITER is to demonstrate the efficiency of the concept of fusion reactor. Requirements to the materials at this stage are severe, but a fusion plant of the next generation will create even more extreme conditions, for work in which, in fact, fundamentally new materials have been developed, including those that we are now investigating, " says Rogozhkin.

Researchers from the National Research Nuclear University, working as part of an IAEA project, have created the most accurate method to date of obtaining the data needed to reliably operate a thermonuclear reactor. The results were published in the Journal of Nuclear Materials.

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