Transport and turbulence studies in the T-10 tokamak

Ossipenko, M. V.

doi:10.1088/0029-5515/43/12/010

Cited by 12 publications

(18 citation statements)

References 18 publications

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“…The paper continues the series of previous publication devoted to the investigations of small-scale density fluctuation characteristics [1][2][3][4] and expands previous results with the new experimental material. The main goals of the paper were the confirmation of the different turbulence types and complete characterization of their properties.…”

Section: Introductionsupporting

confidence: 57%

“…New results are based on previous classification of the fluctuations that identified three main turbulence types [2] shown in the Fig. 6.a,b.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast LFQC is observed for the central and periphery regions. These properties are typical for Trapped Electron Mode (TEM) and Ion Temperature Gradient (ITG) instabilities respectively [2,3].…”

Section: Quasi-coherent Fluctuationsmentioning

confidence: 99%

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3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

et al. 2019

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Previous investigations of small-scale density fluctuation by means of correlation reflectometry in T-10 tokamak revealed the existence of several density fluctuation types and strong radial and poloidal variation of their amplitudes and correlation properties. This paper is focused on the new measurements of the 3D spatial distributions of the amplitudes, the radial correlation lengths and the long range correlations along the field lines for the different turbulence types. The properties of the density fluctuations were systematically studied with the improved reflectometers, data analyzing and acquisition hardware. The density fluctuations were measured by heterodyne correlation reflectometry using ordinary mode. New T-10 antenna set have horn antennae arrays at four places distributed toroidally and poloidally over tokamak torus. The experiments confirmed previously found strong poloidal amplitude asymmetry of the broad band and the quasi-coherent oscillations and the uniform poloidal distribution of stochastic low frequency fluctuations. The presence of those turbulence types was also proved by the measurements of perturbation properties using heavy ion beam probe diagnostic. The radial correlation measurements were performed at four poloidal angles to understand the poloidal dependence of the radial correlation length for the different fluctuation types. The significant decrease of the radial correlation lengths towards the high magnetic field side was observed for quasi-coherent and stochastic low frequency turbulence types. The long range correlations along the field lines were measured by the reflectometers in two cross-section separated by 1/4 of the torus. The reflectometers have the same frequency thus provide reflection from the same magnetic surface. Reflection radii are chosen by the frequency variation of the launched wave from shot to shot in a series of reproducible discharges. The measurements were carried out at the low and the high magnetic field side with two currents and simultaneous reverse of the direction of the toroidal magnetic field and the plasma current. Resonance radii were also calculated using 3D tracing of the magnetic field line and demonstrate good agreement with experiments. These results allow to propose the new approach for the current profile measurements in tokamaks.

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Section: Introductionsupporting

confidence: 57%

“…New results are based on previous classification of the fluctuations that identified three main turbulence types [2] shown in the Fig. 6.a,b.…”

Section: Resultsmentioning

confidence: 99%

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3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

et al. 2019

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“…The specific practical goal of this work is to apply the obtained theoretical results to the interpretation of the data of correlation reflectometry of EM waves in the radio frequency range for diagnosing turbulent plasma in tokamaks. Of particular interest is the analysis of a phenomenon discovered at the T-10 tokamak and called "quasi-coherent oscillations" [41][42][43] (in international terminology, quasi-coherent mode). Subsequently, the same results were obtained on other tokamaks using the same diagnostics-reflectometry (TEXTOR, ToreSupra, KSTAR, HL-2A, and J-TEXT tokamaks).…”

Section: Introductionmentioning

confidence: 99%

New Approach to Cross-Correlation Reflectometry Diagnostics of Nonlocality of Plasma Turbulence

Kukushkin

Kulichenko

2022

Symmetry

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One of the most important properties of stochastic nonlinear processes, including the turbulence of the hydrodynamic motion of continuous media, is distant spatial correlations. To describe them, an approach was proposed by Shlesinger and colleagues based on a linear integro-differential equation with a slowly decaying kernel, which corresponds to superdiffusion (nonlocal) transfer in the regime of Lévy walks (Lévy flights when the finite velocity of the carriers is taken into account). In this paper, we formulate a similar approach that makes it possible to formulate the problem of determining these properties from the scattering spectra of electromagnetic (EM) waves and cross-correlation reflectometry. A universal description of the relationship between the observed symmetric quasi-coherent component in the spectrum of scattered EM waves in plasmas and a process of the Mandelstam–Brillouin scattering type is obtained. It is shown that the nonlocality of spatial correlations of density fluctuations in a turbulent medium is due to long-free-path carriers of the medium’s perturbations, for which the free path distribution function is described by the Lévy distribution. The effectiveness of the proposed method is shown by the example of the interpretation of the data of cross-correlation reflectometry of EM waves in the radio-frequency range for the diagnosis of turbulent plasma in magnetic confinement devices for axisymmetric toroidal thermonuclear plasma.

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“…8 might be the result of such cascade, that is, a large structure replacing small-scale turbulence. The physical mechanism behind such reverse cascade might be mediated by condensation or caused by ECRH switch-off through the effect of subtle changes in the safety factor q profile [13]. Such condensation of the spectral energy has been theoretically predicted by Hasegawa et al [14], and its resulting inverse energy cascade correlated with the generation of large turbulent structures has been observed in experiments [15].…”

Section: Correlation Analysis Of the Density Fluctuation After Ecmentioning

confidence: 90%

Observation of turbulence suppression after electron-cyclotron-resonance-heating switch-off on the HL-2A tokamak

et al. 2011

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The formation of a transient internal transport barrier (ITB) is observed after the electron-cyclotron-resonance-heating (ECRH) switch-off in the HL-2A plasmas, characterized by transient increase of central electron temperature. The newly developed correlation reflectometer provided direct measurements showing reduction of turbulence in the region of steepened gradients for the period of ITB formation triggered by the ECRH switch-off. Furthermore, the reduction of core turbulence is correlated in time with the appearance of a low-frequency mode with a spectrally broad poloidal structure that peaks near zero frequency in the core region. These structures have low poloidal mode number, high poloidal correlation, and short radial correlation and are strongly coupled with high-frequency ambient turbulence. Observation indicates that these structures play important roles in the reduction of the core turbulence and in improvements of the core transport after the off-axis ECRH is turned off.

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Transport and turbulence studies in the T-10 tokamak

Cited by 12 publications

References 18 publications

3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

New Approach to Cross-Correlation Reflectometry Diagnostics of Nonlocality of Plasma Turbulence

Observation of turbulence suppression after electron-cyclotron-resonance-heating switch-off on the HL-2A tokamak

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