Transport of parallel momentum by toroidal ion temperature gradient instability near marginality

Yoon, Eisung; Hahm, T. S.

doi:10.1088/0029-5515/50/6/064006

Cited by 18 publications

(21 citation statements)

References 54 publications

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“…Symmetry breaking due to magnetic field curvature and gradient results in momentum pinch in tokamaks. [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.…”

Section: Introductionmentioning

confidence: 99%

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%

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

2014

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“…Neoclassical models [17][18][19][20][21][22][23] have matched some experimental features, 12,22,24 but predict toroidal viscosities far lower than observed in experiment. 6,[12][13][14][24][25][26][27] Turbulent models have primarily focused on core physics, dominantly using quasilinear approximations, [28][29][30][31][32] mostly based on ITG [33][34][35][36][37][38][39][40] and trapped electron [39][40][41] modes, identifying momentum pinches due to radial electric field (E r ) shear, 38,39 temperature gradients, 28,32 and magnetic inhomogeneity, [32][33][34][35][36]41 as well as residual stress due to a) Electronic mail: tstoltzf@ipp.mpg.de the ion pressure gradient, 29 up-down asymmetric magnetic geometry, 40 the polarization drift, …”

Section: 15mentioning

confidence: 99%

Tokamak-edge toroidal rotation due to inhomogeneous transport and geodesic curvature

Stoltzfus-Dueck

2012

Physics of Plasmas

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In a model kinetic ion transport equation for the pedestal and scrape-off layer, passing-ion drift orbit excursions interact with spatially-inhomogeneous but purely diffusive transport to cause the orbit-averaged diffusivities to depend on the sign of v , preferentially transporting counter-current ions for realistic parameter values. The resulting pedestal-top intrinsic rotation is typically co-current, reaches experimentally relevant values, and is proportional to pedestal-top ion temperature T i | pt over plasma current I p , as observed in experiment. The rotation drive is independent of the toroidal velocity and its radial gradient, representing a residual stress. Co-current spin-up at the L-H transition is expected due to increasing T i | pt and a steepening of the turbulence intensity gradient. A more inboard (outboard) X-point leads to additional co-(counter-) current rotation drive. Beyond intrinsic rotation, comparison of heat and momentum transport reveals that neutral beam injection must be significantly unbalanced in the counter-current direction to cause zero toroidal rotation at the pedestal top.

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“…10,11,[28][29][30] Another symmetry breaking mechanism, which leads to an inward pinch, can come from the interplay of magnetic field curvature and ballooning mode structure in toroidal geometry. 31,32 See Table I of Ref. 31 for a unified illustration of these two symmetry breaking mechanisms from a gyrokinetic theory viewpoint.…”

Section: Nonlinear Residual Stress Generation and The Scaling Of mentioning

confidence: 99%

Nonlinear flow generation by electrostatic turbulence in tokamaks

et al. 2010

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Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEM). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wave number spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond E × B shear. The ITG turbulence driven "intrinsic" torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by "intrinsic" torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a "flow pinch" in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy and particle fluxes, elucidating the roles of resonant and non-resonant particles.

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Transport of parallel momentum by toroidal ion temperature gradient instability near marginality

Cited by 18 publications

References 54 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

Tokamak-edge toroidal rotation due to inhomogeneous transport and geodesic curvature

Nonlinear flow generation by electrostatic turbulence in tokamaks

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Transport of parallel momentum by toroidal ion temperature gradient instability near marginality

Cited by 18 publications

References 54 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

Tokamak-edge toroidal rotation due to inhomogeneous transport and geodesic curvature

Nonlinear flow generation by electrostatic turbulence in tokamaks

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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