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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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2017
Extensive modelling efforts of the plasma response to the resonant magnetic perturbation fields, utilized for controlling the edge localized mode (ELM), help to identify the edge-peeling response as a key factor, which correlates to the observed ELM mitigation in several tokamak devices, including MAST, ASDEX Upgrade, EAST, and HL-2A. The recently …
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2011
Neutral beam injection into reversed magnetic shear DIII-D and ASDEX Upgrade plasmas produces a variety of Alfvénic activity including toroidicity-induced Alfvén eigenmodes and reversed shear Alfvén eigenmodes (RSAEs). These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central sa…
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2008
Core localized Alfvén eigenmodes in DIII-D [J. L. Luxon, Nucl. Fusion 42 , 614 (2002)] and Joint European Torus JET [P. H. Rebut and B. E. Keen, Fusion Technol. 11 , 13 (1987)] plasmas are driven by deuterium neutral beam ions traveling well below the Alfvén speed. Modes are observed in reverse magnetic shear discharges with deuterium ion velocit…
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2006
Reversed shear Alfvén eigenmodes RSAE that were observed in the Joint European Torus (JET) [P. H. Rebut and B. E. Keen, Fusion Technol. 11 , 13 (1987)] and DIII-D [J. L. Luxon, Nucl. Fusion 42 , 614 (2002)] are studied with the ideal magnetohydrodynamic code NOVA-K C. [Z. Cheng, Phys. Rep. 211 , 1 (1992)]. It was found that the frequency behavior …
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2004
A microwave interferometry technique is applied for the first time for detecting a discrete spectrum of Alfvén cascade (AC) eigenmodes excited with fast ions in reversed magnetic shear plasmas of the Joint European Torus. The interferometry measurements of plasma density perturbations associated with ACs show an unprecedented frequency and time re…
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2004
Experimental evidence is presented for the existence of the theoretically predicted odd toroidicity induced Alfve?n eigenmode (TAE) from the simultaneous appearance of odd and even TAEs in a normal shear discharge of the joint European torus. The modes are observed in low central magnetic shear plasmas created by injecting lower hybrid current driv…
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2003
The original description of alpha particle driven instabilities in the Tokamak Fusion Test Reactor in terms of toroidal Alfven eigenmodes (TAEs) remained inconsistent with three fundamental characteristics of the observations: (i) the variation of the mode frequency with toroidal mode number, (ii) the chirping of the mode frequency for a given toro…
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