In recent experiments at the ASDEX Upgrade tokamak the existence of an Edge Resonant Transport Layer (ERTL) was revealed as the main transport mechanism responsible for the measured fast-ion losses in the presence of externally applied 3D fields. The Monte Carlo orbit-following code ASCOT was used to study the fast-ion transport including the plasma response calculated with MARS-F, reproducing a strong correlation of fast-ion losses with the poloidal mode spectra of the 3D fields. In this work, a description of the physics underlying the ERTL is presented by means of numerical simulations together with an analytical model and experimental measurements to validate the results. The degradation of fast-ion confinement is calculated in terms of the variation of the toroidal canonical momentum (δP φ ). This analysis reveals resonant patterns at the plasma edge activated by 3D perturbations and emphasizes the relevance of nonlinear resonances. The impact of collisions and the radial electric field on the ERTL is analyzed. ‡ See the author list of Overview of progress in European Medium Sized Tokamaks towards an integrated plasma-edge/wall solution by H. Meyer et al., Nucl. Fusion 57 102014 2017.

Fast-ion redistribution and loss due to edge perturbations in the ASDEX Upgrade, DIII-D and KSTAR tokamaks M. Garcia-Munoz, S. Äkäslompolo, O. Asunta et al. Spatiotemporal response of plasma edge density and temperature to non-axisymmetric magnetic perturbations at ASDEX Upgrade

Abstract. The impact of Edge Localized Modes (ELMs) and externally applied Resonant and Non-Resonant Magnetic Perturbations (MPs) on fast-ion confinement / transport have been investigated in the ASDEX Upgrade, DIII-D and KSTAR tokamaks. These studies were enabled by coordinated multi-machine experiments and new diagnostic capabilities that provide detailed information on the interaction between energetic particles and instabilities in particle phase-space. Filament-like bursts of fast-ion losses induced by ELMs dominate the losses in H-mode plasmas as measured by fast-ion loss detectors (FILDs) at different toroidal and poloidal positions. In lowcollisionality H-modes, ELM and inter-ELM fluctuations in fast-ion losses are often strongly connected with main ELM properties and edge flows. Filamentary fast-ion losses are observed during ELMs, suggesting a strong interaction between fast-ions and the instabilities concomitant to the ELM cycle, blobs and filaments. Large changes in escaping-ion phase-space are observed within a single ELM. Externally applied MPs have little effect on kinetic profiles, including fast-ions, in high collisionality plasmas with mitigated ELMs while a strong impact on kinetic profiles is observed in low-collisionality, low q 95 plasmas with resonant and non-resonant MPs. During the mitigation / suppression of type-I ELMs by externally applied MPs, the large fast-ion blobs / filaments observed during ELMs are replaced by a loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the NBI prompt loss signal without MPs; a clear synergy in the overall fast-ion transport is observed between MPs and Neoclassical Tearing Modes (NTMs). Measured fast-ion losses show a broad energy and pitch-angle range and are typically on banana orbits that explore the entire pedestal / Scrape-Off-Layer (SOL). The fast-ion response to externally applied MPs presented here may be of general interest for the community to better understand the MP field penetration and overall plasma response. Full orbit simulations indicate that MPs push the loss boundary radially inwards opening and populating the loss cone with particles that would be otherwise well confined.