Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas

Gürcan, Ö. D.; Diamond, P. H.; Hennequin, Pascale; McDevitt, C. J.; Garbet, X.; Bourdelle, C.

doi:10.1063/1.3503624

Cited by 97 publications

(118 citation statements)

References 49 publications

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“…[9][10][11][12][13][14] Conversion of radial inhomogeneity into hk k i asymmetry requires some symmetry breaking mechanisms. 7,8,[15][16][17][18][19] Role of mean E Â B shearing in symmetry breaking, hence in off-diagonal momentum flux, was identified by many authors. 16,18 Recently, G€ urcan et al showed how the mean E Â B shear can lead to the reflectional symmetry breaking of hk k i in ion temperature gradient (ITG) turbulence, resulting in finite parallel residual stress.…”

Section: Introductionmentioning

confidence: 99%

“…18 Reflectional symmetry breaking of k jj here means generation of eigenmode averaged wave number hk jj i 6 ¼ 0 by symmetry breaking of eigenmode about a rational surface, i.e., by j/j 2 ðxÞ 6 ¼ j/jðÀxÞ. Turbulence intensity gradient can also induce hk k i symmetry breaking, 19 which may be an important driver of the intrinsic torque near the top of a transport barrier where a strong fluctuation intensity gradient is present. The process of hk k i symmetry breaking by E Â B shear and/or intensity gradient implies a coupling between intrinsic rotation and transport barrier dynamics, such as internal transport barrier (ITB) formation, which involves steep temperature and/or density gradients (i.e., strong radial inhomogeneity) and the strong E Â B shear and/or the fluctuation intensity gradient (i.e., hk k i symmetry breaking).…”

Section: Introductionmentioning

confidence: 99%

“…39,40 The q-curvature effect can be classified as an element of profile shearing effect. The effect of profile shearing is two fold: (1) to produce gradient in turbulence intensity 19 which can cause residual stress by k jj symmetry breaking that acts at pressure profile curvature region. (2) Eigenmode tilt about the low field side mid-plane h ¼ 0, [41][42][43] which has shown to cause residual stress in global gyrokinetic simulations.…”

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Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

2014

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We present an analytic study of momentum transport of tokamak plasmas in the vicinity of minimum safety factor (q) position in reversed magnetic shear configuration. Slab ion temperature gradient modes with an equilibrium flow profile are considered in this study. Quasi-linear calculations of momentum flux clearly show the novel effects of q-curvature on the generation of intrinsic rotation and mean poloidal flow without invoking reflectional symmetry breaking of parallel wavenumber (k k ). This q-curvature effect originates from the inherent asymmetry in k k populations with respect to a rational surface due to the quadratic proportionality of k k when q-curvature is taken into account. Discussions are made of possible implications of q-curvature induced plasma flows on internal transport barrier formation in reversed shear tokamaks. V C 2014 AIP Publishing LLC. [http://dx

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

2014

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“…One residual stress component has been derived to be due to the gradient of the turbulence intensity field I. 10,11 Including this residual stress is only possible in a transport model where the turbulence intensity is accessible, and thus, this constitutes a unique aspect of this model.…”

Section: Turbulence Spreading Transport Modelmentioning

confidence: 99%

Cold pulse and rotation reversals with turbulence spreading and residual stress

et al. 2016

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Articles you may be interested inTurbulence induced radial transport of toroidal momentum in boundary plasma of EAST tokamak Phys. Plasmas 23, 062309 (2016) Transport modeling based on inclusion of turbulence spreading and residual stresses shows internal rotation reversals and polarity reversal of cold pulses, with a clear indication of nonlocal transport effects due to fast spreading in the turbulence intensity field. The effects of turbulence spreading and residual stress are calculated from the gradient of the turbulence intensity. In the model presented in this paper, the flux is carried by the turbulence intensity field, which in itself is subject to radial transport effects. The pulse polarity inversion and the rotation profile reversal positions are close to the radial location of the stable/unstable transition. Both effects have no direct explanation within the framework of classical transport modeling, where the fluxes are related directly to the linear growth rates, the turbulence intensity profile is not considered and the corresponding residual stress is absent. Our simulations are in qualitative agreement with measurements from ohmically heated plasmas. Rotation reversal at a finite radius is found in situations not displaying saturated confinement, which we identify as situations where the plasma is nearly everywhere unstable. As an additional and new effect, the model predicts a perturbation of the velocity profile following a cold pulse from the edge. This allows direct experimental confirmation of both the existence of residual stress caused by turbulence intensity profiles and fundamental ideas of transport modeling presented here. Published by AIP Publishing.

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“…These ideas focus on the role of "residual stress," P r , that is, the portion of the angular momentum flux that is not proportional to the velocity or to its gradient. 283,284 The divergence of the residual stress constitutes the intrinsic torque. In the enhanced confinement regimes, P r is a function of the temperature gradient.…”

Section: Momentum Transportmentioning

confidence: 99%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only highpower radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing componentsapproaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated a) Paper AR1 1, Bull. Am. Phys. Soc. 58, 21 (2013). b) Invited speaker.

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Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas

Cited by 97 publications

References 49 publications

Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

Cold pulse and rotation reversals with turbulence spreading and residual stress

20 years of research on the Alcator C-Mod tokamak

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Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas

Cited by 97 publications

References 49 publications

Momentum transport in the vicinity of qmin in reverse shear tokamaks due to ion temperature gradient turbulence

Momentum transport in the vicinity of qmin in reverse shear tokamaks due to ion temperature gradient turbulence

Cold pulse and rotation reversals with turbulence spreading and residual stress

20 years of research on the Alcator C-Mod tokamak

Contact Info

Product

Resources

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Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence