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Observation of Magnetohydrodynamic Instabilities in Heliotron J Plasmas

S. Yamamoto, K. Nagasaki, Y. Suzuki, T. Mizuuchi, H. Okada, S. Kobayashi, B. Blackwell, K. Kondo, G. Motojima, N. Nakajima, Y. Nakamura, C. Nührenberg, Y. Torii, S. Watanabe, F. Sano

Fusion Science and Technology / Volume 51 / Number 1 / January 2007 / Pages 92-96

Technical Paper / Stellarators /

Two kinds of magnetohydrodynamics instability are observed in electron cyclotron heating and neutral beam injection-heated Heliotron J plasmas. One is the pressure-driven interchange modes with m = 2/n = 1 and m = 5/n = 3 and low frequency (fexp < 20 kHz), which are observed in the plasma with a rational surface of /2 = 0.5 or 0.65. The other is the energetic ion-driven global Alfvén eigenmodes (GAEs) in the Alfvén frequency range. To identify the observed GAEs, the frequency of the observed mode with shear Alfvén spectra calculated by CAS3D3 is compared. The interchange mode with m = 5/n = 3 and bursting GAE with intense magnetic fluctuations may affect the bulk plasma confinement and energetic ion transport, respectively.

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