Multi-Dimensional Structure of the Electric Field in Tokamak H-Mode

Kasuya, Naohiro; Itoh, K.

doi:10.1585/jspf.81.553

Cited by 8 publications

(37 citation statements)

References 41 publications

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“…7 (b)). If the fluctuation structure with m/n = 1/1 or 2/1 has a radial wave number, k r , comparable with toroidal and poloidal wave numbers, the radial propagation velocity is approximately equal to the diamagnetic drift velocity [33]. A possibility of the long-range fluctuation is discussed later.…”

Section: Spatiotemporal Structure Of Radiation Temperature and Long Dmentioning

confidence: 99%

Long Range Temperature Fluctuation in LHD

Inagaki

Tokuzawa

Itoh

et al. 2011

Plasma and Fusion Research

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We report a detailed correlation technique to identify the long-range temperature fluctuation in the Large Helical Device. Correlation hunting has successfully realized the observation of electron temperature fluctuations, which are characterized by their correlation length comparable to the plasma minor radius, with low frequency of ∼ 1-3 kHz, ballistic radial propagation (at a speed of ∼1 km/s, of the order of diamagnetic drift velocity), spatial mode number of m/n = 1/1 (or 2/1), and amplitude of ∼2% at the maximum. Bicoherence analysis confirmed their nonlinear coupling with local microscopic turbulent fluctuations. This long-range temperature fluctuation is a possible carrier of fast propagation in transport processes observed so far. We also comment on the theoretical interpretation.

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Section: Spatiotemporal Structure Of Radiation Temperature and Long Dmentioning

confidence: 99%

Long Range Temperature Fluctuation in LHD

Inagaki

Tokuzawa

Itoh

et al. 2011

Plasma and Fusion Research

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“…The theoretical framework for describing bifurcation of the radial structure as well as poloidal inhomogeneity in tokamak edge plasmas is based on the momentum balance equation [6]. The flux-surface-averaged poloidal component of the momentum balance can be simplified to be shear bulk…”

Section: Model Equationmentioning

confidence: 99%

“…This iterative process is appropriate, because a condition V r / V p << 1 is satisfied, even if a strong poloidal shock exists [6].…”

Section: Model Equationmentioning

confidence: 99%

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Two dimensionally steep structure of the electric field in tokamak H-mode

Kasuya¹,

Itoh²

2008

Nucl. Fusion

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Abstract. The rapid formation of a density pedestal on an L/H transition has been raising a question why the rapid density evolution is induced. Formation of a poloidal shock structure is predicted in H-mode transport barriers, and consideration of the two-dimensional structure both in the radial and poloidal directions is inevitable to clarify the formation mechanism of the H-mode pedestal. The analyses are carried out with edge plasmas in tokamak H modes, which are induced either spontaneously or by electrode biasing. Two-dimensional structures of the potential, density and flow velocity are calculated with the momentum conservation equation. The validity of the one-dimensional L/H transition theory and the iterative process to obtain the two-dimensional structure are confirmed by our analysis. A steep electric field structure both in the radial and poloidal directions is obtained. The two-dimensional electric field induces radial ion fluxes, which increase in the H-mode transport barrier and affect the electric field. If the Boltzmann relation is violated, radial electron fluxes are induced, and affect the density evolution. Reduction of anomalous transport by the steep gradient of the radial electric field, and generation of the particle fluxes associated with the two-dimensional structure influence the rapid formation of the steep gradients in H-mode plasmas. A transport model including both effects is constructed to reveal the self-consistent mechanism of the density pedestal formation in the L/H transition.

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“…The steep change in the poloidal direction arises in the electrostatic potential of plasma, so that a strong poloidal electric field is generated at the shock. Figure 6 illustrates an example of poloidal shock [85]. The variation of density in the poloidal direction and the localized poloidal electric field are shown.…”

Section: Examples Of Predictionsmentioning

confidence: 99%

Symmetry-Breaking of Turbulence Structure and Position Identification in Toroidal Plasmas

Itoh

Nagashima

et al. 2018

Plasma and Fusion Research

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As a result of the progresses in the study of plasma turbulence, the picture of 'multiple-scale turbulence' is widely accepted, and the 'nonlinear excitation, nonlocal interaction, probabilistic transition' views have been developed. Along the paths of these progresses, importance of new problem, i.e., the symmetry-breaking of turbulence structure (such as up-down asymmetry, excitation of streamer, etc.) is gradually recognized. In this topical review article, we revisit these issues, and illuminate the possibilities that the new progresses (which will be brought about by studying the symmetry-breaking of turbulence) are expected. Examining theoretical predictions and preceding experimental achievements, new advancements, which will be realized, are explained. The experimental study of symmetry-breaking of turbulence structure ultimately requires to measure fluctuations (at all scales) over the whole plasma cross-section simultaneously. In addition, new type of demands can be imposed in measuring of fluctuations over the whole plasma cross-section simultaneously. One of such demands is the accuracy of the measurement position. Problems in this aspect are also discussed. This concise review is used to identify what will be discovered and how it will be reached in future experiments, in the subject of the symmetry-breaking of turbulence structure.

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Multi-Dimensional Structure of the Electric Field in Tokamak H-Mode

Cited by 8 publications

References 41 publications

Long Range Temperature Fluctuation in LHD

Long Range Temperature Fluctuation in LHD

Two dimensionally steep structure of the electric field in tokamak H-mode

Symmetry-Breaking of Turbulence Structure and Position Identification in Toroidal Plasmas

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