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UKAEA-CCFE-PR(24)2132024
In this work, the first experimental attempts at controlling Edge Localised Modes (ELMs) via the application of resonant magnetic perturbations (RMPs) on theMAST Upgrade tokamak are reported. Moderate ELM mitigation was achieved in low betaN by the application of n=1 3D fields, at the cost of inducing a ’benign’ locked mode. At higher betaN how…
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UKAEA-CCFE-PR(22)092022
Experiments in ASDEX Upgrade (AUG) and JET with the ITER-like wall (JET-ILW) are performed to separate the pedestal and core contributions to confinement in H-modes with different main ion masses. A strong isotope mass dependence in the pedestal is found which is enhanced at high gas puffing. This is because the ELM type changes when going fro…
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UKAEA-CCFE-CP(20)712020
The fast-ion transport has been investigated in low-collisionality discharges at ASDEX Upgrade and TCV using offaxis neutral beams. In both devices Alfven eigenmode activity was observed which does, however, not strongly affect the global fast-ion confinement. In contrast, charge exchange losses have been identified to have a strong effect. At TCV …
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2018
Access conditions for full suppression of edge localised modes (ELMs) by magnetic perturbations (MP) in low density high confinement mode (H-mode) plasmas are studied in the ASDEX Upgrade tokamak. The main empirical requirements for full ELM suppression in our experiments are: 1. The poloidal spectrum of the MP must be aligned for best plasma respo…
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UKAEA-CCFE-PR(19)182019
A numerical survey of the plasma response in ASDEX Upgrade ELM control experiments is conducted, to clarify the role of triangularity in the suppression mechanism. The pedestal pressure increases with triangularity consistent with previous work [2], which modestly boosts the peeling response. However, the peeling response decreases with increasi…
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UKAEA-CCFE-CP(18)042018
An edge resonant transport layer has been found to explain many aspects of fast-ion confinement under symmetry breaking 3D edge perturbations, such as edge localized modes (ELMs) and externally applied magnetic perturbations (MPs). Experimental measurements in the ASDEX Upgrade (AUG) tokamak show that fast-ion losses in the presence of symmetry bre…
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UKAEA-CCFE-PR(18)692018
The impact of the three-dimensional (3D) tokamak geometry from external magnetic perturbations (MPs) on the local edge stability has been examined in high confinement mode (H-mode) plasmas with edge localised modes (ELMs) in ASDEX Upgrade. The 3D geometry has been probed using rigidly rotating MP fields. The measured distortions of the plasma bound…
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CCFE-PR(17)702017
It has been previously demonstrated in (Li et al 2016 Nuclear Fusion 56 126007) that the optimum upper/lower coil phase shift ΔΦopt for alignment of RMP coils for ELM mitigation depends sensitively on q95, and other equilibrium plasma parameters. Therefore, ΔΦopt is expected to vary widely during the current ramp …
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CCFE-PR(16)072016
The plasma response to the vacuum resonant magnetic perturbation (RMP) fields, produced by the ELM control coils in ASDEX Upgrade experiments, is computationally modelled using the MARS-F/K codes [Liu Y.Q. et al 2000 Phys. Plasmas 7 3681; Liu Y.Q. et al 2008 Phys. Plasmas 15 112503]. A systematic investigation is carried out, considering various pl…
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CCFE-PR(15)112015
Sustained Edge Localised Mode (ELM) mitigation has been achieved on MAST and AUG using RMPs with various toroidal mode numbers over a wide range of low to medium collisionality discharges. The ELM energy loss and peak heat loads at the divertor targets have been reduced. The ELM mitigation phase is typically associated with a drop in plasma density…
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