2019, Wang, H. Q., Stepanenko, A. A., Степаненко, Александр Александрович

© 2019, Pleiades Publishing, Ltd.Abstract: Recent experimental observations of divertor plasma turbulence at the ASDEX Upgrade tokamak have demonstrated the onset of strong fluctuations of plasma radiation intensity in the near X-point region within the inner divertor leg, when the machine was operating with the pronounced asymmetry in detachment of plasma between the inner and outer divertors. As been recently shown, one of the possible mechanisms responsible for these fluctuations can be related to the current-convective instability (CCI). In this contribution, we assess whether the CCI can drive turbulence with spatial and temporal parameters similar to those observed lately in DIII-D experiments. It is demonstrated that the CCI drives saturated plasma fluctuations, dominated by low-frequency modes with toroidal wavelengths on the order of the machine circumference in the inner divertor region—features that are similar to turbulence characteristics found in experiments.

2025, СРЕДИН, В. Г., ВОЙЦЕХОВСКИЙ, А. В., МЕЛЕХОВ, А. П., РАМАКОТИ, Р. Ш., СТЕПАНЕНКО, А. А., АНДРЕЙЧИКОВ, К. С., Степаненко, Александр Александрович, Мелехов, Андрей Петрович, Рамакоти, Рави Шрираджа

Рассмотрены процессы, протекающие в структурах поверхностный окисел – антимонида индия под действием мягкого рентгеновского излучения. Показано, что облучение приводит к генерации радиационных дефектов на поверхности кристалла.

2024, Stepanenko, A. A., Krat, S. A., Степаненко, Александр Александрович, Крат, Степан Андреевич

2021, Zhdanov, V. M., Stepanenko, A. A., Степаненко, Александр Александрович

© 2021, Springer Science+Business Media, LLC, part of Springer Nature.The authors have studied the influence of the adsorption and surface diffusion of one component of a binary gas mixture on pore walls on the effect of separation of the gas mixture during its flow through a nanosize porous membrane in a free molecular regime. A capillary porous-medium model obtained by the momentum-balance method was taken as a basis for analysis. Expressions have been determined for the separation factor and the concentration jump of the adsorbed component for an assigned pressure difference on the membrane, which make it possible to analyze the influence of the initial concentration of the adsorbable component and of the temperature on the separation effect. Calculations have been performed of the concentration jump for a number of commercial gas mixtures (CO2/H2, CO/H2, CH4/H2, and N2/He). It has been shown that taking account of surface diffusion may lead to appreciable variations (of several tens of percent) of the obtained values from Knudsen values of the effect in the absence of adsorption.

2022, Klemazov, K. V., Isaev, E. I., Stepanenko, A. A., Stepanov, V. A., Исаев, Евгений Игоревич, Степаненко, Александр Александрович, Степанов, Владимир Александрович

© 2022, Pleiades Publishing, Ltd.Abstract: The results of experimental determination of fluorozirconate glass crystallization temperatures by the methods of DSC and spectroscopy have been compared. It has been shown that the crystallization starting temperature, determined by an increase in the light scattering intensity, is 40° below the crystallization point, as seen by DSC. The effect of laser irradiation on the crystallization temperatures of glasses has been detected.

2023, Stepanenko, A. A., Marenkov, E. D., Pshenov, A. A., Kukushkin, A. S., Степаненко, Александр Александрович, Маренков, Евгений Дмитриевич

2026, Stepanenko, A. A., Степаненко, Александр Александрович

2021, Zaznoba, V. A., Zhdanov, V. M., Stepanenko, A. A., Степаненко, Александр Александрович

© 2021 Author(s).The binary gas mixture flow, diffusion, and heat transfer through a long tube in the near-continuum regime (moderately small Knudsen numbers) are analyzed. The system of linearized third-order moment equations, obtained by Grad's method, is used. An expression for the total mass flux of a binary gas mixture is deduced by using the extension of the procedure, proposed in the work by Zhdanov ["Slip and barodiffusion phenomena in slow flows of a gas mixture,"Phys. Rev. E 95, 033106 (2017)] for the study of slip phenomena in slow flows of a gas mixture. Relations for diffusion and heat fluxes are determined from the initial system of moment equations, averaged over the channel cross section, and supplied with several moments of the distribution function at the channel wall found with the modified Maxwell method. Analytical formulas for kinetic coefficients of the Onsager matrix, which connect averaged fluxes and gradients of the corresponding thermodynamic quantities, are obtained. It is shown that the employed approach automatically ensures the validity of the reciprocal relations for the cross terms in the Onsager matrix. The results of calculations of the derived kinetic coefficients for several binary mixtures of noble gases (He-Ar, Ne-Ar, and He-Xe) are presented and compared with numerical data found by the discrete velocity method on the basis of the linearized Boltzmann equation with the McCormack model.

2024, СРЕДИН, В. Г., СТЕПАНЕНКО, А. А., МЕЛЕХО, А. П., РАМАКОТИ, Р. Ш., АНДРЕЙЧИКОВ, К. С., Степаненко, Александр Александрович, Рамакоти, Рави Шрираджа, Мелехов, Андрей Петрович

Рассмотрено влияние облучения мягкого рентгеновского излучения на структуру анодный поверхностный окисел – антимонид индия. Показано, что изменение ее характеристик вероятно связано с возникновением заряженных состояний в слое окисла.

2020, Wang, H. Q., Watkins, J. G., Guo, H. Y., Leonard, A. W., Stepanenko, A. A., Степаненко, Александр Александрович

© 2020 Author(s).An MHD mode with a frequency of <10 kHz has been identified near the inner strike point from various diagnostics, i.e., divertor Langmuir probes, magnetics sensors, and interferometers, but does not appear in the upstream and core diagnostics. This MHD mode is associated with magnetic oscillations of ≳5 G, has a long wavelength in the toroidal direction with toroidal mode number n = 1, but is localized in a narrow radial region of a few cm. The mode appears when the outer strike point remains attached and the inner strike point nearly detaches, grows with increasing density, and eventually weakens and vanishes as the outer strike point detaches. This mode results in particle flux with an order of magnitude higher than the background plasmas near the inner strike point. The mode characteristics are consistent with the Current-Convective-Instability theory prediction. Initial simulations based on experimental input have found oscillations with similar frequencies but weaker amplitude.