Impact of magnetic perturbation coils on the edge radial electric field and turbulence in ASDEX Upgrade

Fietz, S.; Müller, Hans; Lunt, T.; Simon, Patrick; Suttrop, W.; Maraschek, M.; Happel, T.; Viezzer, E.

doi:10.1088/0741-3335/57/1/014035

Cited by 36 publications

(37 citation statements)

References 41 publications

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“…In particular, a region of large positive E r , along the LCFS, can be noticed. This is a confirmation of the well-known presence of a positive E r in the stochastic edge of a tokamak [22,23,38,63,64,65,66,67,68]. But, if we focus on this region, we can note also a modulation in the poloidal angle, strictly linked to the magnetic topology, too: E r has a minimum in between the XP and the OP, and an absolute maximum in correspondence of the XP.…”

Section: Maps Of Plasma Potential: Experiments and Simulationssupporting

confidence: 76%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted with simulations with the Hamiltonian guiding center code Orbit. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for theseeffects. An analytical model for the plasma potential is implemented in the code Orbit, and analyses of ion and electron radial diffusion show that both ion-and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggests that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

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Section: Maps Of Plasma Potential: Experiments and Simulationssupporting

confidence: 76%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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“…Significant E r profile change at the plasma edge usually accompanies the application of RMPs [20][21][22][23][24][25][26]. Our results suggest that the E × B flow shear may influence ELMs through its influence on the kink/peeling instabilities.…”

Section: E × B Flow Shear Drive Of the Linear Low-n Modes Of Eho In Tmentioning

confidence: 70%

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

Wan

Wang

et al. 2017

Nucl. Fusion

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A new model for the edge harmonic oscillations (EHOs) in the quiescent H-mode regime has been developed, which successfully reproduces the recent observations in the DIII-D tokamak. In particular, at high E × B flow shear only a few low-n kink modes remain unstable at the plasma edge, consistent with the EHO behavior, while at low E × B flow shear, the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior. The model is based on a new mechanism for destabilizing low-n kink/peeling modes by the E × B flow shear, which underlies the EHOs, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the 2D pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drive as the parallel wavenumber increases significantly away from the rational surface at the plasma edge where the magnetic shear is also strong. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.

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“…Resonant magnetic perturbations (RMPs) are planned for ITER for the purpose of ELMs control. As is known from several experiments on DIII-D [1], MAST [2] and ASDEX Upgrade [3] the RMPs lead to formation of the stochastic layer inside the separatrix in its vicinity, the radial electric field becomes less negative or even positive here, and density pump out takes place. This effect is most pronounced for the low density (low collisionality) shots.…”

Section: Introductionmentioning

confidence: 90%

“…The key element of the model is the balance of the radial electron current in a stochastic magnetic field and the radial ion neoclassical current which is controlled by a neoclassical ion radial conductivity. Modeling of the RMPs impact with the B2SOLPS5.2 code with account of additional electron stochastic conductivity is able to reproduce the main features observed in the experiments: change of the radial electric field, plasma acceleration in the co-current direction and density pump out [2][3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Modeling of ITER Edge Plasma in the Presence of Resonant Magnetic Perturbations

Rozhansky

Veselova

Voskoboynikov

et al. 2016

Contrib. Plasma Phys.

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The modeling of the ITER edge is performed with the use of the code B2SOLPS5.2 in the presence of the electron conductivity caused by RMPs as well as for the reference case with the same input parameters but without RMPs. The radial electric field close to the neoclassical one is obtained without RMPs. Even the modest level of RMPs changes the direction of the electric field and causes the toroidal spin-up of the edge plasma. At the same time the pump-out effect is small.

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Impact of magnetic perturbation coils on the edge radial electric field and turbulence in ASDEX Upgrade

Cited by 36 publications

References 41 publications

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

Modeling of ITER Edge Plasma in the Presence of Resonant Magnetic Perturbations

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