13 results on '"S. I. Lashkul"'
Search Results
2. Particle source and radial electric field shear as the factors affecting the LH-transition possibility and dynamics in a tokamak
- Author
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A. Yu. Yashin, D. V. Kouprienko, V. A. Kornev, A. A. Belokurov, G. I. Abdullina, Susan Leerink, A. V. Petrov, Timo Kiviniemi, V. V. Bulanin, P. Niskala, S. I. Lashkul, N. A. Zhubr, L. G. Askinazi, A. S. Tukachinsky, A. D. Gurchenko, E. Z. Gusakov, S. V. Lebedev, L. Chôné, D. V. Razumenko, and S. V. Krikunov
- Subjects
Physics ,Tokamak ,Shear (geology) ,law ,Electric field ,Particle source ,Plasma ,Mechanics ,Condensed Matter Physics ,Mathematical Physics ,Atomic and Molecular Physics, and Optics ,law.invention - Published
- 2020
3. Runaway electron studies with hard x-ray and microwave diagnostics in the FT-2 lower hybrid current drive discharges
- Author
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I.A. Polunovsky, V.O. Naidenov, A. B. Altukhov, D. V. Kouprienko, V. G. Kiptily, V.V. Plyusnin, A.V. Sidorov, D. Gin, S. I. Lashkul, D.N. Doinikov, A. E. Shevelev, Santosh P. Pandya, E.M. Khilkevitch, I.N. Chugunov, L. A. Esipov, V.V. Rozhdestvensky, and M. Iliasova
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Nuclear and High Energy Physics ,Materials science ,Tokamak ,Plasma parameters ,Electron ,Plasma ,Condensed Matter Physics ,01 natural sciences ,Electromagnetic radiation ,010305 fluids & plasmas ,Computational physics ,law.invention ,Physics::Plasma Physics ,law ,0103 physical sciences ,Cathode ray ,Limiter ,010306 general physics ,Microwave - Abstract
Studies of the super-thermal and runaway electron behavior in ohmic and lower hybrid current drive FT-2 tokamak plasmas have been carried out using information obtained from measurements of hard x-ray spectra and non-thermal microwave radiation intensity at the frequency of 10 GHz and in the range of (53 ÷ 78) GHz. A gamma-ray spectrometer based on a scintillation detector with a LaBr3(Ce) crystal was used, which provides measurements at counting rates up to 107 s−1. Reconstruction of the energy distribution of RE interacting with the poloidal limiter of the tokamak chamber was made with application of the DeGaSum code. Super-thermal electrons accelerated up to 2 MeV by the LH waves at the high-frequency pumping of the plasma with low density ~ 2 × 1013 cm−3 and then up to 7 MeV by vortex electric field have been found. Experimental analysis of the runaway electron beam generation and evolution of their energy distribution in the FT-2 plasmas is presented in the article and compared with the numerical calculation of the maximum energy gained by runaway electrons for given plasma parameters. In addition, possible mechanisms for limiting the maximum energy gained by the runaway electrons are also calculated and described for a FT-2 plasma discharge.
- Published
- 2017
4. Observation of the ETG mode component of tokamak plasma turbulence by the UHR backscattering diagnostics
- Author
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D. V. Kouprienko, M. Yu. Kantor, E. Z. Gusakov, S. I. Lashkul, V. V. Dyachenko, A. Yu. Stepanov, L. A. Esipov, A. B. Altukhov, and A. D. Gurchenko
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Physics ,Nuclear and High Energy Physics ,Tokamak ,Turbulence ,business.industry ,Plasma turbulence ,Mode (statistics) ,Resonance ,Condensed Matter Physics ,Computational physics ,law.invention ,Optics ,Physics::Plasma Physics ,law ,Wave mode ,Wavenumber ,business ,Wave number spectrum - Abstract
A fine scale drift wave mode possessing unusually high frequency 2?3?MHz and radial wave number is observed using the correlative upper hybrid resonance backscattering technique at the FT-2 tokamak under conditions when the ETG mode should be unstable. The radial wave number spectrum of turbulence is measured and shown to be maximal at values 120?170?cm?1 corresponding to the largest ETG instability growth rate.
- Published
- 2007
5. Investigation of small-scale tokamak plasma turbulence by correlative UHR backscattering diagnostics
- Author
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D. V. Kouprienko, A. B. Altukhov, V. V. Bulanin, E. Z. Gusakov, A. Yu. Stepanov, L. A. Esipov, A. D. Gurchenko, A. V. Petrov, M. Yu. Kantor, and S. I. Lashkul
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Physics ,Tokamak ,Turbulence ,Resonance ,Plasma ,Condensed Matter Physics ,Spectral line ,law.invention ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,law ,Physics::Space Physics ,Wavenumber ,Electron temperature ,Atomic physics ,Phase velocity - Abstract
Fine scale turbulence is considered nowadays as a possible candidate for the explanation of anomalous ion and electron energy transport in magnetized fusion plasmas. The unique correlative upper hybrid resonance backscattering (UHR BS) technique is applied at the FT-2 tokamak for investigation of density fluctuations excited in this turbulence. The measurements are carried out in Ohmic discharge at several values of plasma current and density and during current ramp up experiment. The moveable focusing antennas set have been used in experiments allowing probing out of equatorial plane. The radial wave number spectra of the small-scale component of tokamak turbulence are determined from the correlation data with high spatial resolution. Two small-scale modes possessing substantially different phase velocities are observed in plasma under conditions when the threshold for the electron temperature gradient mode excitation is overcome. The possibility of plasma poloidal velocity profile determination using the UHR BS signal is demonstrated.
- Published
- 2006
6. Processes in SOL plasma at the transition into improved confinement mode in FT-2 tokamak
- Author
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P. R. Goncharov, M. Yu. Kantor, A. D. Lebedev, D. V. Kouprienko, V. N. Budnikov, S. V. Shatalin, E. O. Vekshina, L. A. Esipov, S. I. Lashkul, V. V. Dyachenko, and E. R. Its
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Materials science ,Tokamak ,Plasma parameters ,Magnetic confinement fusion ,Plasma ,Condensed Matter Physics ,law.invention ,symbols.namesake ,Nuclear Energy and Engineering ,law ,Electric field ,Limiter ,symbols ,Langmuir probe ,Plasma diagnostics ,Atomic physics - Abstract
Studies of processes in the scrape-off layer (SOL) of the tokamak show a direct influence of periphery effects on confinement parameters of the plasma core. This paper illustrates experimentally observed transport barrier formation initialized by the low hybrid (LH) heating of the hydrogen plasma. The experimental data near last close flax surface (LCFS) and in SOL were obtained by means of an enhanced movable multielectrode Langmuir probe and spatially resolved spectroscopic technique retooled with additional helium puffing. The edge diagnostics show a strong change of a radial electric field and plasma parameters near LCFS. The alteration at the plasma edge is generated by high LH ion heating. It was found that the L-H transition is accompanied by a noticeable reconstruction of the poloidal and radial plasma parameters profiles in the SOL and in the limiter shadow region.
- Published
- 2002
7. Poloidal inhomogeneity of turbulence in the FT-2 tokamak by radial correlation Doppler reflectometry and gyrokinetic modelling
- Author
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A. B. Altukhov, E. Z. Gusakov, L. A. Esipov, P. Niskala, D. V. Kouprienko, S. I. Lashkul, A. Yu. Stepanov, A. D. Gurchenko, Susan Leerink, M. Yu. Kantor, M. A. Irzak, and N. V. Teplova
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Physics ,Tokamak ,Turbulence ,business.industry ,Computation ,Plasma ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Computational physics ,law.invention ,symbols.namesake ,Optics ,Distribution function ,Nuclear Energy and Engineering ,Deuterium ,Physics::Plasma Physics ,law ,0103 physical sciences ,symbols ,010306 general physics ,business ,Reflectometry ,Doppler effect - Abstract
The poloidal dependence of the drift-wave turbulence characteristics is investigated at the FT-2 tokamak by radial correlation Doppler reflectometry (RCDR) technique and using the full distribution function global gyrokinetic modelling by ELMFIRE code. The poloidal variation of the turbulence radial correlation length from 0.2–0.55 cm is demonstrated both by measurement and computation. The turbulence correlation length rapidly decreases from the top of the poloidal cross-section to the high field side and then steadily grows in the poloidal direction. A well-pronounced excess of the turbulence radial correlation length in deuterium over its value in hydrogen discharges is demonstrated.
- Published
- 2016
8. Impact of isotopic effect on density limit and LHCD efficiency in the FT-2 experiments
- Author
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E. Z. Gusakov, Artur Perevalov, D. V. Kouprienko, M. A. Irzak, L. A. Esipov, A. N. Saveliev, V. V. Dyachenko, S. V. Shatalin, A. Yu. Stepanov, M. Yu. Kantor, A. D. Gurchenko, A. B. Altukhov, and S. I. Lashkul
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Nuclear and High Energy Physics ,Tokamak ,Materials science ,Isotope ,Hydrogen ,Resonance ,chemistry.chemical_element ,Plasma ,Condensed Matter Physics ,law.invention ,Ion ,chemistry ,Deuterium ,law ,Density limit ,Atomic physics - Abstract
Current drive by lower hybrid waves (LHCD) is the most effective method to sustain the plasma current, but it is feasible only at the plasma density not exceeding some density limit nDL. In the present work the main attention is paid to the investigation of this effect on the FT-2 (R = 0.55 m, a = 0.08 m, BT ≤ 3 T, Ipl = 19–40 kA, f0 = 920 MHz) tokamak. The dependence of LHCD efficiency on isotopic plasma content (hydrogen/deuterium) is studied. Characteristic features of such an experiment are a strong influence of the isotope plasma composition on the LH resonance density nLH. For hydrogen plasma nLH ≈ 3.5 × 1019 m−3, while for deuterium plasma nLH ≈ 2 × 1020 m−3. The suppression of the LHCD and beginning of the interaction of LH waves with ions are determined by the hydrogen/deuterium plasma density rise. In the hot hydrogen plasma (Te(r = 0 cm) ≈ 700 eV) the density limit nDL of LHCD is approximately equal to the resonance value nLH ≈ nLC, where nLC is the point of linear conversion. In the hot deuterium plasma one could expect an increase of nDL because of a much higher value of nLH ≥ nLC ≈ 1020 m−3. However it appeared that the observed density limit for LHCD generation nDL ≈ (3.5–4) × 1019 m−3 is not determined by nLH. The role of parametric instabilities in CD switch-off is considered in both cases. The cooling of the plasma column and density rise could lead to a reduction of the threshold for the parametric decay of f0 and result in early suppression of LHCD. In both cases the LHCD was inversely proportional to the density, which corresponds to the theoretical predictions. In order to analyse the experimentally observed LHCD efficiency the GRILL3D and FRTC codes have been used.
- Published
- 2015
9. Anomalous transport and multi-scale drift turbulence dynamics in tokamak ohmic discharge as measured by high resolution diagnostics and modeled by full-fgyrokinetic code
- Author
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D. V. Kouprienko, Victor Bulanin, E. Z. Gusakov, L. A. Esipov, A. D. Gurchenko, A. B. Altukhov, A. V. Petrov, N V Teplova, Salomon Janhunen, S. I. Lashkul, T. Korpilo, M. Yu. Kantor, Timo Kiviniemi, Jukka Heikkinen, and Susan Leerink
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Physics ,Tokamak ,Turbulence ,Spectral density ,Probability density function ,Condensed Matter Physics ,Thermal diffusivity ,law.invention ,Computational physics ,symbols.namesake ,Classical mechanics ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,law ,Electric field ,symbols ,Transport phenomena ,Doppler effect - Abstract
Quantitative reproduction of selected micro-, meso- and macro-scale transport phenomena as measured in the FT-2 tokamak is reached by Elmfire global full-f nonlinear gyrokinetic particle-in-cell simulation predictions. A detailed agreement with mean equilibrium flows, oscillating fine-scale zonal flows and turbulence radial correlation length observed by a set of sophisticated microwave backscattering techniques, as well as a good fit of the thermal diffusivity data in the central and gradient region of discharge are demonstrated. Both the shift and the broadening of the power spectrum of synthetic and experimental Doppler reflectometry diagnostics have been found to overlap perfectly at various radial positions, indicating similar rotation and spreading of the selected density fluctuations. At the same time similar radial electric field dynamics, spatial structure and outward geodesic acoustic mode (GAM) propagation have been observed by comparisons of the probability distribution function, the dominant frequency, the coherence and the cross-phase of the simulated and experimentally measured radial electric field fluctuations, identifying the turbulent driven GAM as a key contributor to the observed strong temporal variation of the radial electric field affected by impurity ions.
- Published
- 2013
10. Energy balance studies during ECRH experiments in FT-1 Tokamak
- Author
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M.M. Larionov, S G Kalmykov, D.G. Bulyginsky, T.Yu. Akatova, A.I. Tokunov, G. T. Razdobarin, S.G. Goncharov, V.I. Ivanov, M. Yu. Kantor, L.S. Levin, N.V. Shustova, and S. I. Lashkul
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Tokamak ,Materials science ,Energy balance ,Time evolution ,Plasma ,Condensed Matter Physics ,Computational physics ,law.invention ,Pulse (physics) ,Nuclear magnetic resonance ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,law ,Absorption (electromagnetic radiation) ,Energy (signal processing) ,Microwave - Abstract
The energy confinement degradation was found in the FT-1 Tokamak in ECRH experiments. The time evolution of Te profile during the ECRH pulse was measured by the laser scattering, and the local energy balance was analysed by a numerical code. The peripherical absorption of microwave power and the fast development of some additional energy loss mechanism due to the action of microwaves on the plasma are supposed to be the reasons for confinement degradation.
- Published
- 1988
11. Gyrokinetic characterization of the isotope effect in turbulent transport at the FT-2 tokamak.
- Author
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P Niskala, A D Gurchenko, E Z Gusakov, A B Altukhov, L A Esipov, M Yu Kantor, T P Kiviniemi, D Kouprienko, T Korpilo, S I Lashkul, S Leerink, A A Perevalov, and R Rochford
- Subjects
TOKAMAKS ,TURBULENCE ,ISOTOPES ,PLASMA confinement ,SIMULATION methods & models - Abstract
Isotope effect allows fusion devices to perform better when heavier hydrogen isotopes are used as fuel, but the reason for this improvement is not yet understood. We present the first direct evidence of the isotope effect on particle confinement in the FT-2 tokamak and investigate it via gyrokinetic simulations. Experimental measurements for comparable hydrogen and deuterium discharges show that the particle confinement time increases by 40% for the heavier isotope species. The isotope effect on particle flux is reproduced in global and local gyrokinetic simulations. Global ELMFIRE simulations demonstrate a systemic reduction in particle fluxes across the radial range, showing a ratio of fluxes at the edge and at . Local GENE simulations agree qualitatively with the result. Besides the fluctuation level, smaller scales and a favorable shift in the cross-phase between the turbulent fluctuations are found to contribute to the isotope effect in the simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
12. The isotope effect in turbulent transport control by GAMs. Observation and gyrokinetic modeling.
- Author
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A D Gurchenko, E Z Gusakov, P Niskala, A B Altukhov, L A Esipov, T P Kiviniemi, T Korpilo, D V Kouprienko, S I Lashkul, S Leerink, A A Perevalov, and M A Irzak
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ISOTOPES ,TURBULENCE ,FLUID dynamics ,WAVELENGTHS ,DEUTERIUM compounds ,HEAT flux - Abstract
A comparative investigation of the isotope effect in multi-scale anomalous transport phenomena is performed both experimentally by highly localized turbulence diagnostics in comparable hydrogen and deuterium FT-2 tokamak discharges and theoretically with the help of global gyrokinetic modeling. Substantial excess of the geodesic acoustic mode (GAM) amplitude, radial wavelength and correlation length in a wide spatial region of deuterium discharge resulting in stronger modulation of drift-wave turbulence level is demonstrated by both approaches. A larger turbulence radial correlation length is found at LFS in D-discharge in experiment and a stronger modulation of gyrokinetic particles and energy fluxes is shown there by the gyrokinetic code. The gyrokinetic modeling demonstrated comparable levels of drift wave density and electric field fluctuations in hydrogen and deuterium discharges. Nevertheless, the mean value of the ion energy and particle anomalous flux provided by modeling shows the systematic isotope effect at all radii. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
13. Turbulence and anomalous tokamak transport control by Geodesic Acoustic Mode.
- Author
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A. D. Gurchenko, E. Z. Gusakov, P. Niskala, A. B. Altukhov, L. A. Esipov, T. P. Kiviniemi, D. V. Kouprienko, M. Yu. Kantor, S. I. Lashkul, S. Leerink, A. A. Perevalov, and T. Korpilo
- Abstract
The elementary process of turbulence control by Geodesic Acoustic Modes (GAMs) leading to modulation of its level at the GAM frequency is for the first time supported by experimental observations at the FT-2 tokamak. The modulation effect is confirmed by the global total-distribution-function gyrokinetic modelling of the tokamak discharge, predicting strong modulation of the electron thermal diffusivity induced by GAMs, which propagates inward and possesses the GAM temporal and spatial structure. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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