The influences of electrode biasing (EB) on toroidal rotation and turbulent (toroidal) momentum transport at the plasma edge have been experimentally studied in the J-TEXT tokamak. In the absence of bias (i.e. the bias current I b  =  0 A), plasma toroidal rotation at the edge of the confined region is intrinsically towards the co-I p direction (parallel to plasma current); in the presence of bias, edge rotation can be greatly modified, and shows positive correlation with the bias current. As the dominant term in the turbulent momentum flux, the toroidal-radial Reynolds stress term is found to give rise to an intrinsic torque in the experiments. The local momentum balance is provided by a viscous damping-like term on the velocity. Moreover, the existence of intrinsic torque at the edge is directly verified by cancelling out the local rotation under negative bias (I b  ≈  −60 A). The corresponding intrinsic torque density at the plasma edge is about 0.65 N m−2, in the co-I p direction. Further comparison shows that this intrinsic torque can be reasonably explained by the measured residual stress, providing direct evidence for the hypothesis that the residual stress is the origin of the intrinsic rotation.

The acceleration of the co-current toroidal rotations around resonant surfaces by resonant magnetic perturbations (RMPs) through turbulence is presented. These experiments were performed using a Langmuir probe array in the edge plasmas of the J-TEXT tokamak. This study aims at understanding the RMP effects on edge toroidal rotations and exploring its control method. With RMPs, the flat electron temperature Te profile due to magnetic islands appears around resonant surfaces [K. J. Zhao et al., Nucl Fusion, 55, 073022 (2015)]. When the resonant surface is closer to the last closed flux surface, the flat Te profile vanishes with RMPs. In both cases, the toroidal rotations significantly increase in the direction of the plasma current around resonant surfaces with RMPs. The characteristics of turbulence are significantly affected by RMPs around resonant surfaces. Turbulence intensity profile changes and the poloidal wave vector kθ increases with RMPs. The power fraction of the turbulence components in the ion diamagnetic drift direction increases with RMPs. 2The measurements of turbulent Reynolds stresses are consistent with that the toroidal flows can be driven by turbulence. The estimations of the energy transfer between turbulence and toroidal flows suggest that turbulence energy transfers into toroidal flows. The result has the implication of the intrinsic rotation being driven by RMPs via turbulence.

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