Absolute dissipative drift-wave instabilities in tokamaks

Chen, L.; Chance, M. S.; Cheng, C. Z.

doi:10.1088/0029-5515/20/7/011

Cited by 28 publications

(36 citation statements)

References 16 publications

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“…In addition, the fluctuations spread from the SOL into the core at reduced amplitudes and shorter wavelengths, which produces a core toroidal wavenumber spectrum that is much lower in amplitude at longer wavelengths. These simulated wavenumber spectra agree with the experimentally measured spectra in several features [1]: lower amplitude in the core at longer wavelengths [2], higher amplitude in the SOL at longer wavelengths [3], decreasing trend towards shorter wavelengths in the SOL.…”

Section: Discussionsupporting

confidence: 84%

“…In previous local, linear simulations [13], the SOL was found to be unstable while the core was stable. A variety of effects were studied, and core stability was found to be due to the stabilizing FRC traits of [1] short electron transit length [2], radially increasing magnetic field on the outboard side, and [3] strong FLR effects due to weak magnetic field. In the initial linear simulations of this section, nonlocal effects were numerically removed, effectively localizing the physics of the simulations.…”

Section: Fluctuations Spreading From Sol To Corementioning

confidence: 99%

“…An ideal field-reversed configuration (FRC) is an elongated prolate compact toroid (CT) with purely poloidal magnetic fields, consisting of two regions separated by a separatrix: an inner, closed field-line core region and an outer, open fieldline scrape-off layer (SOL) region [1,2]. Research interest in the FRC has persisted due to potential reactor benefits [1]: β (the ratio of plasma pressure to magnetic energy density) near unity suggests cheaper magnetic energy costs than low β approaches such as the tokamak [2]; compact shape simplifies construction of the device hull and external magnetic field coils [3]; on-axis SOL which may be connected to the divertor arbitrarily far from the FRC core; and [4] the lack of toroidal magnetic fields radically changes the magnetic topology and the consequential stability of the plasma [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Cross-separatrix simulations of turbulent transport in the field-reversed configuration

et al. 2019

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Recent local simulations of the field-reversed configuration (FRC) have reported drift-wave stability in the core and instability in the scrape-off layer (SOL). However, experimental measurements indicate the existence of fluctuations in both FRC core and SOL, with much lower amplitude fluctuations measured in the core. With the updated cross-separatrix capabilities of the simulation code used in this paper, nonlinear turbulence simulations find that linear instabilities grow in the SOL, generating fluctuations which spread from SOL to core. After saturation of the linear instabilities, a balance of the inward spread and local damping in the core is achieved. The steady state toroidal wavenumber spectrum shows lower amplitude core fluctuations and larger SOL fluctuations with amplitude decreasing towards shorter wavelengths, which are consistent with experimental measurements.

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Section: Discussionsupporting

confidence: 84%

Section: Fluctuations Spreading From Sol To Corementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cross-separatrix simulations of turbulent transport in the field-reversed configuration

et al. 2019

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“…Our model of drift wave turbulence is an extended form of the Hasegawa-Wakatani ͑HW͒ equations 9 that includes magnetic field inhomogeneity in the radial direction and the resulting interchange driven modes. 10 We refer to this as the extended Hasegawa-Wakatani ͑EHW͒ model. This model was studied in three-dimensional ͑3D͒ by Sugama et al 11 and in 2D in Refs.…”

Section: Introductionmentioning

confidence: 99%

The effects of nonuniform magnetic field strength on density flux and test particle transport in drift wave turbulence

2009

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The extended Hasegawa–Wakatani equations generate fully nonlinear self-consistent solutions for coupled density n and vorticity ∇2ϕ, where ϕ is electrostatic potential, in a plasma with background density inhomogeneity κ=−∂ ln n0/∂x and magnetic field strength inhomogeneity C=−∂ ln B/∂x. Finite C introduces interchange effects and ∇B drifts into the framework of drift turbulence through compressibility of the E×B and diamagnetic drifts. This paper addresses the direct computation of the radial E×B density flux Γn=−n∂ϕ/∂y, tracer particle transport, the statistical properties of the turbulent fluctuations that drive Γn and tracer motion, and analytical underpinnings. Systematic trends emerge in the dependence on C of the skewness of the distribution of pointwise Γn and in the relative phase of density-velocity and density-potential pairings. It is shown how these effects, together with conservation of potential vorticity Π=∇2ϕ−n+(κ−C)x, account for much of the transport phenomenology. Simple analytical arguments yield a Fickian relation Γn=(κ−C)Dx between the radial density flux Γn and the radial tracer diffusivity Dx, which is shown to explain key trends in the simulations.

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“…Here, for simplicity, we will assume the ions to be cold and will ignore the electron temperature gradient. Using fluid descriptions, the eigenvalue equation in the presence of a velocity field can be derived in a straightforward way [5][6][7]:…”

mentioning

confidence: 99%

Role of Parallel Flow in the Improved Mode on the STOR-M Tokamak

et al. 2002

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A novel feature of the H-mode induced by compact torus injection on the STOR-M tokamak is observed. There is almost no change in the radial electric field profiles during and after the L-H transition. The usual hypothesis of the E x B shear stabilization mechanism is therefore unlikely to play a role in this transition. A new mechanism of the stabilization of microinstabilities by parallel flow is suggested as the plausible cause for the transition to this improved regime.

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Absolute dissipative drift-wave instabilities in tokamaks

Abstract: Contrary to previous theoretical predictions, it is shown that the dissipative drift-wave instabilities are absolute in tokamak plasmas. The existence of unstable eigenmodes is shown to be associated with a new eigenmode branch induced by the finite toroidal coupling.

Cited by 28 publications

References 16 publications

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

The effects of nonuniform magnetic field strength on density flux and test particle transport in drift wave turbulence

Role of Parallel Flow in the Improved Mode on the STOR-M Tokamak

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