Anomalous parallel momentum transport due to E×B flow shear in a tokamak plasma

Casson, F. J.; Peeters, A. G.; Camenen, Y.; Hornsby, W. A.; Snodin, A. P.; Strintzi, D.; Szepesi, G.

doi:10.1063/1.3227650

Cited by 80 publications

(150 citation statements)

References 47 publications

(42 reference statements)

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“…Note, the TEM and ITG tilt angles found here are very similar to the ones used in a previous study [5]. The fact that the ITG data points at both radial locations require smaller tilt angles to optimise the quantitative agreement with the measurements suggests that there are at least two main processes contributing to the poloidal tilt of the turbulent eddies: one proportional to the sign of the turbulence propagation, such as profile shearing [32] or intensity gradient [31], and the second independent of ω r , such as E × B shear [26,27,28,29].…”

Section: Comparison To Predictions From Linear Gyrokinetic Calculsupporting

confidence: 69%

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

McDermott¹,

Angioni²,

Conway³

et al. 2014

Nucl. Fusion

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Abstract. The ASDEX Upgrade intrinsic rotation database has been expanded to include a large number of measurements from Ohmic L-mode discharges covering a wide range of plasma densities, currents, and magnetic fields. This database was then used to study the rotation behavior across the transition from linear to saturated Ohmic confinement (LOC/SOC). At low collisionailty the plasma is in the LOC regime and the toroidal rotation profile is in the co-current direction. As the collisionality is increased and the plasma transitions from LOC to SOC, the core rotation decreases resulting in a hollow, counter-current profile. Even deeper in the SOC regime, however, a second reversal back toward the co-current direction occurs. Linear gyrokinetic calculations indicate that these reversals can not be explained by a transition from a trapped electron mode (TEM) to an ion temperature gradient (ITG) dominated regime. Rather, the analysis indicates that the intrinsic normalised rotation gradient, u', depends strongly on local plasma parameters, in particular on R/L ne . Taken together with turbulent particle transport theory, these results suggest that the coto counter-current directed rotation reversal occurs in the TEM regime due to profile changes and not due to transition from TEM to ITG. The second reversal back to the co-current direction is explained by the reduction of R/L ne observed in ITG dominated plasmas. Lastly, a simple linear model for the residual stress assuming a fixed poloidal tilt angle of the turbulent eddies was applied to the database. This model is able to capture the main parameter dependencies observed in the data and demonstrates that at least two processes contributing to the poloidal tilt of the turbulent eddies are needed to reproduce the experimentally observed u' values: one proportional to the sign of the turbulence propagation and the second independent of ω r .

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Section: Comparison To Predictions From Linear Gyrokinetic Calculsupporting

confidence: 69%

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

McDermott¹,

Angioni²,

Conway³

et al. 2014

Nucl. Fusion

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“…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). Gyrokinetic simulations have shown the generation of intrinsic rotation from the hk k i symmetry breaking by mean E Â B shear [20][21][22][23] and turbulence intensity gradient 20 and up-down asymmetry of equilibrium magnetic topology. 24,25 Gyrokinetic simulations have also shown residual stress from profile shearing effects.…”

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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“…The effect of E Â B shearing and Ã effects (local approximation) are neglected. Note that when the E Â B shearing rate is proportional to the rotation gradient, it enters only the diagonal momentum flux [28,29]. The gyrokinetic equation solved in GKW is formulated in the frame rotating with the toroidal angular velocity of the plasma !…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Experimental Evidence of Momentum Transport Induced by an Up-Down Asymmetric Magnetic Equilibrium in Toroidal Plasmas

et al. 2010

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The first experimental evidence of parallel momentum transport generated by the up-down asymmetry of a toroidal plasma is reported. The experiments, conducted in the Tokamak à Configuration Variable, were motivated by the recent theoretical discovery of ion-scale turbulent momentum transport induced by an up-down asymmetry in the magnetic equilibrium. The toroidal rotation gradient is observed to depend on the asymmetry in the outer part of the plasma leading to a variation of the central rotation by a factor of 1.5-2. The direction of the effect and its magnitude are in agreement with theoretical predictions for the eight possible combinations of plasma asymmetry, current, and magnetic field.

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Anomalous parallel momentum transport due to E×B flow shear in a tokamak plasma

Cited by 80 publications

References 47 publications

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

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

Experimental Evidence of Momentum Transport Induced by an Up-Down Asymmetric Magnetic Equilibrium in Toroidal Plasmas

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Anomalous parallel momentum transport due to E×B flow shear in a tokamak plasma

Cited by 80 publications

References 47 publications

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

Core intrinsic rotation behaviour in ASDEX Upgrade ohmic L-mode plasmas

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

Experimental Evidence of Momentum Transport Induced by an Up-Down Asymmetric Magnetic Equilibrium in Toroidal Plasmas

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