Персона: Степаненко, Александр Александрович
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Институт лазерных и плазменных технологий
Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.
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- ПубликацияОткрытый доступВлияние неупругих столкновений частиц на процессы переноса в частично ионизованной многокомпонентной плазме(НИЯУ МИФИ, 2014) Степаненко, А. А.; Степаненко, Александр Александрович; Жданов, В. М.
- ПубликацияТолько метаданныеSpatial–Temporal Properties of Current-Convective Turbulence in Divertor Plasma under DIII-D-Like Detached Conditions(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.
- ПубликацияТолько метаданныеBoundary slip phenomena in multicomponent gas mixtures(2019) Zaznoba, V. A.; Stepanenko, A. A.; Zhdanov, V. M.; Степаненко, Александр Александрович© 2019 Author(s).The slip phenomena in multicomponent gas mixtures are studied. The moment equations, derived from the linearized Boltzmann equation by using the 13-moment approximation of the Grad's method, are used to obtain the full (containing the contribution from the Knudsen layer) and asymptotic (valid far from the plane physical boundary of the domain) expressions for the nonequilibrium macroscopic parameters of the mixture species. The latter relations are employed to deduce the expressions for the mixture slip velocity and the viscous, thermal, and diffusion slip coefficients by using the modified Maxwell method and the diffuse-specular model of molecule scattering on the wall. The derived relations for the slip coefficients are given in the convenient form expressed in terms of basic transport coefficients, such as partial viscosity and thermal conductivity coefficients, diffusion and thermal diffusion coefficients, and coefficients of molecule momentum accommodation at the wall. The expressions found are used to calculate the slip coefficients for binary (He-Ar) and ternary (He-Ar-Xe) gas mixtures. The numerical results are in good agreement with the data calculated by using other methods.
- ПубликацияОткрытый доступImpact of divertor plasma parameters on characteristics of current-convective turbulence under DIII-D-like detached conditions(2019) Wang, H. Q.; Krasheninnikov, S. I.; Stepanenko, A. A.; Степаненко, Александр Александрович© 2019 Author(s).Recent observations of turbulence in plasma of a DIII-D inner divertor revealed the formation of poloidally localized fluctuations with frequencies in the low-kilohertz range, when the machine was operating in the fluctuating state of detachment. This phenomenon can be related to the onset of the current-convective instability (CCI). In this contribution, we use the basic physical model of the instability to simulate the saturated current-convective turbulence under the DIII-D-like detached conditions. Parameter scans of turbulence characteristics are performed. The spatial and temporal spectra of fluctuations are obtained and compared with the available experimental data. It is demonstrated that simulations are able to qualitatively reproduce most of the distinct features of turbulence found in the experiments, indicating that the CCI can be a plausible mechanism responsible for plasma activity recently observed in DIII-D.
- ПубликацияТолько метаданныеEnhanced particle flux due to localized divertor MHD instability in DIII-D tokamak(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.