Drift waves in stellarator geometry

Nadeem, M; Lewandowski, J. L. V.; Gardner, Henry

doi:10.1088/0741-3335/42/2/310

Cited by 12 publications

(14 citation statements)

References 19 publications

(27 reference statements)

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“…Hence, in this representation we have two degrees of freedom for the positioning represented by the magnetic flux surface s and a field line label α. In a simple slab geometry, the frequency and the growth rate are directly proportional to χ when χ < 1 and are inversely proportional to χ when χ > 1 [15]. The parameter χ appears in the wave equation through the perpendicular wave vector k⊥ and controls the magnitude of the perpendicular wave vector, k⊥ , along the normal to the magnetic flux surface.…”

Section: The Drift Wave Modelmentioning

confidence: 99%

“…The parameter χ appears in the wave equation through the perpendicular wave vector k⊥ and controls the magnitude of the perpendicular wave vector, k⊥ , along the normal to the magnetic flux surface. The frequency and the growth rate peak at θ k = 0 and χ = 1 for the H1-NF stellarator [15]. These values are selected for the numerical calculations of the most unstable modes on a given magnetic flux surface.…”

Section: The Drift Wave Modelmentioning

confidence: 99%

“…Waltz and Boozer [10] studied radial localization of drift mode turbulences in a general stellarator geometry and argued that the localization of these modes strongly depends on LMS and curvature. Persson et al [14,15] investigated drift wave spectrum in a fully three-dimensional stellarator equilibrium using the cold ion model. They found a wide spectrum of drift modes strongly depending upon the density profile and wavelength.…”

Section: Introductionmentioning

confidence: 99%

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Geometrical effects on drift wave stability in low shear stellarator plasmas

Nasim

Rafiq

2003

Plasma Phys. Control. Fusion

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Modern stellarators are designed with neoclassical transport in mind, potentially leading to anomalous transport originating from drift wave turbulence as the primary cause of energy and particle losses. It is therefore of interest to consider the influence of details of geometry on drift wave stability. In this paper the eigenvalue drift wave equation is therefore solved numerically in fully three-dimensional stellarator geometries using the ballooning mode formalism. The correlation between the details of the configurations such as local magnetic shear (LMS), normal curvature, geodesic curvature and magnetic field strength and the drift wave spectrum is discussed for two different stellarator configurations. A detailed discussion of the localization of the most unstable modes is presented and analysed. It is found that the most unstable modes are localized where the stabilizing effect of integrated LMS is minimum or where the coupling between the integrated LMS and geodesic curvature is strong. Since the more the modes are localized the stronger they will be influenced by the local geometrical effects, the most unstable modes are also highly localized.

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Section: The Drift Wave Modelmentioning

confidence: 99%

Section: The Drift Wave Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geometrical effects on drift wave stability in low shear stellarator plasmas

Nasim

Rafiq

2003

Plasma Phys. Control. Fusion

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“…This is quite similar to what we observed in the H1-NF case. 26,29 The effect of the ballooning parameter ⌰ k on the normalized growth rate and frequency is shown in Fig. 9.…”

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confidence: 99%

Unstable ion-temperature-gradient modes in the Wendelstein 7-X stellarator configuration

2002

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The linear stability of the ion-temperature-gradient modes (ITG) in the electrostatic limit is examined in the short wavelength region by using a two fluid reactive model in fully three-dimensional Wendelstein 7-X (W7-X) stellarator [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525] geometry. The spectrum of stable and unstable modes and their real frequencies and eigenfunctions are calculated. The effects of density gradients, temperature gradients, temperature ratios, wavevector, ballooning angle, curvature and local magnetic shear on the ITG mode are also investigated. The frequency and growth rate of the most unstable ITG mode is calculated and visualized for a specific magnetic flux surface. For the equilibrium under investigation both localized and extended eigenmodes are found. The effect of small and large temperature ratios, small and large density gradients as well as large local magnetic shear are all found to be stabilizing. The highest growth rates are found at the outer part of the surface where the local magnetic shear is small and normal curvature is unfavorable.

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“…A similar mode is also seen in H-1 at very low fields ͑Ͻ0.15 T͒, but a clear connection with local curvature or magnetic well has not been found so far. Persson et al 43 have recently treated drift modes in full helical stellarator geometry.…”

Section: Stabilitymentioning

confidence: 99%

Results from helical axis stellarators

Blackwell

2001

Physics of Plasmas

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Helical axis stellarators produce magnetic surfaces of high rotational transform and moderate shear solely by means of external currents, with the promise of high β. Several machines with quite different toroidal, helical, and “bumpy” Fourier components of magnetic field are now producing results, including high quality magnetic surfaces, confinement mode transitions, configuration studies, and confinement consistent with International Stellarator Scaling (ISS95) scaling up to Te∼2 keV. These devices permit concept evaluation over an unprecedented configuration space, and allow basic comparisons with those designed by established and alternative optimization strategies.

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Drift waves in stellarator geometry

Cited by 12 publications

References 19 publications

Geometrical effects on drift wave stability in low shear stellarator plasmas

Geometrical effects on drift wave stability in low shear stellarator plasmas

Unstable ion-temperature-gradient modes in the Wendelstein 7-X stellarator configuration

Results from helical axis stellarators

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