Effect of Plasma Rotation on Sawtooth Stabilization by Beam Ions
Authors: N.N. Gorelenkov, M.F.F. Nave, R. Budny, C.Z. Cheng, G.Y. Fu, J. Hastie, J. Manickam, and W. Park
Presented at: the 27th European Physical Society's (EPS) Conference on Controlled Fusion and Plasma Physics, June 12-16, 2000, Budapest, Hungary. A "Provisional Collection of Submitted Contributions" can be found at the following web site: http://www.eps2000.kfki.hu (active as of August 16, 2000). Papers are in PDF format.
The sawtooth period in JET ELM-free H-Mode plasmas is increasing with Neutral Beam Injection (NBI) power. For injected power PNBI 12MW no large sawtooth crash is observed during the ELM-free period. However, as the edge stability is improved and external kink modes and ELMs are delayed, a possible sawtooth crash at a high plasma beta becomes a concern. In JET DT experiments, delaying sawteeth was found to be crucial in the quest for high fusion power [1]. Fast particles are known to provide stabilizing effect on sawteeth (see for example[2]), however, sawtooth stabilization by NBI ions is not clearly understood, since NBI ions are usually not "fast" enough to stabilize the m/n = 1/1 internal kink mode which is believed to cause the crash. In order to understand the observed sawteeth stabilization in tokamak experiments with NBI heating, the internal kink m/n = 1/1 mode stability of JET plasmas was modeled using the NOVA-K code[3], which is also benchmarked with the nonperturbative version of NOVA[4] and the M3D code[5]. Comparison of m/n = 1/1 mode stabilization by NBI ions in JET and TFTR and application of the nonlinear w*-stabilization criteria[6] is given.