Abstract. In this paper the manipulation of power deposition on divertor targets at DIII-D by application of resonant magnetic perturbations (RMPs) for suppression of large Type-I edge localized modes (ELMs) is analysed. We discuss the modification of the ELM characteristics by the RMP applied. It is shown, that the width of the deposition pattern in ELMy H-mode depends linearly on the ELM deposited energy, whereas in the RMP phase of the discharge those patterns are controlled by the externally induced magnetic perturbation. It was also found that the manipulation of heat transport due to application of small, edge resonant magnetic perturbations (RMP) depends on the plasma pedestal electron collisionality . We compare in this analysis RMP and no RMP phases with and without complete ELM suppression. At high , the heat flux during the ELM suppressed phase is of the same order as the inter-ELM and the no-RMP phase. However, below this collisionality value, a slight increase of the total power flux to the divertor is observed during the RMP phase. This is most likely caused by a more negative potential at the divertor surface due to hot electrons reaching the divertor surface from the pedestal area along perturbed, open field lines and/or the density pump out effect.

Abstract. A study of three-dimensional perturbed magnetic field structures and transport for edge localized mode control experiments with resonant magnetic perturbations at DIII-D is presented. We focus on ITER-Similar Shape plasmas at ITER relevant electron pedestal collisionalities ν * e ∼ 0.2. This study is performed in comparison to results from TEXTOR-Dynamic Ergodic Divertor circular limiter plasmas. For both experiments the magnetic field structure is analyzed in the vacuum paradigm -superimposing the external RMP field on the unperturbed equilibrium. At TEXTOR this description holds for normalized poloidal flux Ψ N > 0.7 without tearing modes driven by the RMP field. For DIII-D H-mode plasmas the validity of this approach still needs to be established. In this paper a method is discussed to diagnose the degree of edge stochastization based on a comparison between modeled magnetic footprints on the divertor targets and experimental data. Clear evidence is presented for the existence of a generic separatrix perturbation causing striation of target particle fluxes. However, heat fluxes into these striations are small. This observation can be explained by accounting for the different heat and particle source locations and the 3D trajectories of the open, perturbed field lines towards the divertor target. Analysis of the transport characteristics filling the perturbed separatrix lobes based on initial EM C3/EIREN E modeling suggests the existence of open field lines connecting the stochastic edge to the target pattern. However, the width and inward most extent of the stochastic layer can not yet be quantified.

In this paper the results of a systematic experimental assessment of the plasma edge rotation and radial electric field with application of resonant magnetic perturbation (RMP) are presented. The results are based on the radially resolved measurement of the poloidal (v pol) and toroidal (v tor) rotation. It is shown that the radial electric field E r can be deduced from the radial force balance when small amplitude resonant magnetic perturbations are applied to the plasma boundary (B r /B tor ∼ 10−4). Both v pol and v tor spin-up in the ion-diamagnetic-drift and co-current direction, respectively, with increasing external perturbation field (Δv pol ∼ 15 km s−1, Δv tor ∼ 2–5 km s−1) yielding an increase in E r by ΔE r,max = 9 kV m−1. The toroidal rotation increases over the whole radius while the poloidal rotation shows distinct local features driving the evolution of the E r -profiles. Depending on the edge safety factor a local (at the q = 5/2 rational surface) increase in the shear rate Ω E × B (ΔΩ q=5/2 = 1.4 × 105 s−1) or reduced shearing can occur. Increased shearing is correlated with an improved particle confinement with an increase in the particle confinement time by Δτp = +40%. Increasing the local resonant amplitude by 30% induces a reduced density level, the so-called RMP induced pump-out. At this confinement stage the shear rate decreases by 15% correlated with a significant drop in particle confinement (Δτp = −30%). Field line tracing in the vacuum approximation gives indications towards explaining the threshold behaviour connecting the shearing rate, confinement stages and magnetic topology to the amount of applied RMP. However, this basic approach does not account for plasma response and the results presented are linked in the discussion section to recent results on the link between rotation and plasma response as well as on the transport features of RMP.

In this paper, results of a direct comparison of TEXTOR and DIII-D experiments with resonant magnetic perturbation (RMP) fields are presented. This comparison of resistive L-mode plasmas at TEXTOR with highly conductive H-mode plasmas at DIII-D is useful to identify generic physics mechanisms during application of RMP fields with a strong field line pitch angle alignment in the plasma edge. A reduction in the pedestal electron pressure pe with increasing extension of the vacuum modelled stochastic layer and pe recovery with decreasing layer width is found caused by a q95 resonant reduction in the edge (0.8 < ΨN < 0.95) electron temperature Te(q95) on both devices. For RMP edge-localized mode (ELM) suppressed H-mode plasmas at DIII-D, the gradients ∇Te and nominal values of Te are reduced in this edge region while increasing in the pedestal (0.95 < ΨN < 1.0) with RMP field applied and both are highly dependent on q95. In contrast, an increase in the central ion temperature with strong steepening of the ion temperature profile at mid-radius is found—again being highly dependent on q95. However, these resonant thermal transport effects are only seen in high triangularity plasmas revealing a strong shape dependence of the thermal transport. In contrast to the highly q95 dependent thermal transport features, the reduction of ne—known as density pump out—shows a much weaker dependence on q95. We show the potential to reduce the RMP induced particle pump out by fine tuning of the RMP spectral properties. At low resonant field amplitudes enhanced particle confinement is seen in high-field side limited L-mode discharges on both devices while higher resonant field amplitudes yield particle pumps out.

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