MHD characteristics in the high beta regime of the Large Helical Device
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.
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