Characteristics of internal transport barrier under reactor relevant condition in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; Ichige, Hisashi; Bucalossi, J.*; Marty, V.*; Ide, Shunsuke; Koide, Yoshihiko; Kamada, Yutaka; JT-60 Team

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature () in the central region decreased even with edge fuelling. The decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity () estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased was recovered and good ITB was sustained with enhanced pedestal pressure. The -ITB also degraded significantly when stiffness feature was strong in the electron temperature () profile against electron cyclotron heating (ECH). The value of in the ITB region increased with the electron thermal diffusivity (), indicating existence of clear relation between ion and electron thermal transport. On the other hand, -ITB unchanged or even grew, when stiffness feature was weak in the profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the -ITB degradation case and shorter in the -ITB unchanging case.