Confinement degradation and transport of energetic ions due to Alfvn eigenmodes in JT-60U weak shear plasmas

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Cheng, C. Z.*; Matsunaga, Go; Kusama, Yoshinori; Fukuyama, Atsushi*; Nishitani, Takeo; Morioka, Atsuhiko; Sasao, Mamiko*; Baba, Mamoru*; JT-60 Team

Confinement degradation of energetic ions due to Alfvn Eigenmodes (AEs) induced by negative-ion-based neutral beam injection for the classical confinement is quantitatively evaluated for the first time. AEs, whose frequency largely sweep and then saturate as the minimum value of the safety factor decrease, have been observed in JT-60U. These mode behavior can be explained by RSAEs and the transition from RSAEs to TAEs. Measured total neutron emission rate in the presence of these AEs is compared with that predicted by a classical theory. As a result, confinement degradation of energetic ions is confirmed. Line-integrated neutron emission profile is also compared with that predicted when assuming that the confinement is classical. The result indicates energetic ions are transported from core region of the plasma due to these AEs.