The effect of off-axis neutral beam injection on sawtooth stability in ASDEX Upgrade and Mega-Ampere Spherical Tokamak

作者：Chapman I T^*; de Bock M F; Pinches S D; Turnyanskiy M R; Igochine V G; Maraschek M; Tardini G

来源：Physics of Plasmas, 2009, 16(7): 072506.

DOI：10.1063/1.3187905

• discharges (electric)
• drift instability
• kink instability
• plasma beam injection heating
• plasma toroidal confinement
• sawtooth instability
• Tokamak devices

Sawtooth behavior has been investigated in plasmas heated with off-axis neutral beam injection in ASDEX Upgrade [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)] and the Mega-Ampere Spherical Tokamak (MAST) [A. Sykes , Nucl. Fusion 41, 1423 (2001)]. Provided that the fast ions are well confined, the sawtooth period is found to decrease as the neutral beam is injected further off-axis. Drift kinetic modeling of such discharges qualitatively shows that the passing fast ions born outside the q=1 rational surface can destabilize the n=1 internal kink mode, thought to be related to the sawtooth instability. This effect can be enhanced by optimizing the deposition of the off-axis beam energetic particle population with respect to the mode location.

• 出版日期2009-7