Effect of ECH/ECCD on Sawtooth Oscillations in NB-heated Plasmas in JT-60U
ISAYAMA Akihiko, IDE Shunsuke, IKEDA Yoshitaka, SUZUKI Takahiro, KAJIWARA Ken and JT-60 team
Japan Atomic Energy Research Institute, Naka, Ibaraki 311-0193, Japan
Abstract.
Sawtooth period and amplitude during electron cyclotron (EC) wave injection to plasmas heated by neutral beams are investigated. Significant decrease in sawtooth period is observed for EC injection inside the inversion radius in co-direction: the normalized sawtooth period τST/Te(0)1.5 reaches 1/10 of that in ohmic heating phase, which shows strong destabilization effect (τST and Te(0) are sawtooth period and central electron temperature, respectively.). Sawtooth amplitude for co-EC injection is more than twice as large as that for counter-EC injection under the same discharge condition except the direction of the injected EC wave. Sawtooth amplitude normalized by the sawtooth period, which is a measure of heat expelled per unit time, significantly increases during co-EC injection, which fact suggests that heat in the core region can be efficiently expelled by EC injection in co-direction inside the inversion radius.