Observation of energetic-ion losses induced by various mhd instabilities in the Large Helical Device (LHD)

K. Ogawa, M. Isobe, K. Toi, F. Watanabe, D. A. Spong, A. Shimizu, M. Osakabe, S. Ohdachi, S. Sakakibara

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Abstract

Energetic-ion losses induced by toroidicity-induced Alfvén eigenmodes (TAEs) and resistive interchange modes (RICs) were observed in neutral-beam heated plasmas of the Large Helical Device (LHD) at a relatively low toroidal magnetic field level (≤0.75 T). The energy and pitch angle of the lost ions are detected using a scintillator-based lostfast ion probe. Each instability increases the lost ions having a certain energy/pitch angle. TAE bursts preferentially induce energetic beam ions in co-passing orbits having energy from the injection energy E = 190keV down to 130 keV, while RICs expel energetic ions of E = 190 keV down to ∼130 keV in passing-toroidally trapped boundary orbits. Loss fluxes induced by these instabilities increase with different dependences on the magnetic fluctuation amplitude: nonlinear and linear dependences for TAEs and RICs, respectively.

Original languageEnglish
Article number084005
JournalNuclear Fusion
Volume50
Issue number8
DOIs
StatePublished - Aug 2010

Funding

FundersFunder number
Japan Society for the Promotion of Science21360457

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