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The highest volume averaged beta values Beta-t of 2.2% at Beta-t = 0.75 T (gas puff) and 2.4% at Beta-t = 1.3 T (pellet) in helical devices have been achieved in LHD. The Beta-t dependence of MHD activities has been investigated in NBI plasmas. The n/m = 1/2 mode, excited in the core region, and the i - = 1 resonant modes, in the peripheral region, have been observed. Both of the fluctuation amplitudes increase with Beta-t and pressure gradient. The strong n/m = 1/2 mode, which affects the plasma profile, has been observed in high Beta-t discharges, and the abrupt disappearance of the mode leads to restoration of the Te profile. Violent instabilities, which terminate the plasma and degradation of global energy confinement, have not been observed so far.

Additional information

Authors: SAKAKIBARA S ET AL, National Institute for Fusion Science, Toki (JP);YAMAMOTO S ET AL, Department of Energy Engineering and Science, Nagoya University (JP);ASHIKAWA N ET AL, Department of Fusion Science, Graduate University for Advanced Studies, Hayama (JP);TAKAHASHI H, Princeton Plasma Physics Laboratory, Princeton University, Princeton (US);COOPER W A, Centre de recherches en physique des plasmas, Ecole Polytechnique Federale de Lausanne (CH)
Bibliographic Reference: An article published in: Nuclear Fusion, September 2001,Vol. 41 (9) 1123-1300
Record Number: 200214713 / Last updated on: 2002-05-16
Original language: en
Available languages: en