18th IAEA Fusion Energy Conference

Dynamic Behavior of Transport in Normal and Reversed Shear Plasmas with Internal Barriers in JT-60U

S. V. Neudatchin^1,2), T. Takizuka²⁾, Yu. N. Dnestrovskij¹⁾, H. Shirai²⁾, T. Fujita²⁾, A. Isayama²⁾, Y. Kamada²⁾, Y. Koide²⁾
1) Nuclear Fusion Institute, RRC "Kurchatov Institute", Moscow, Russia
2) Japan Atomic Energy Research Institute, Naka Fusion Research Establishment Naka-machi, Naka-gun, Ibaraki-ken 311-0193, Japan

Abstract.
Transport evolution in reverse shear (RS) and normal shear (NrS) JT-60U tokamak plasmas with internal transport barrier (ITB) is described as a combination of various fast and slow time scales processes. Abrupt in time and wide in space (~0.3 of minor radius) variations of electron and ion heat diffusivities dc_e,i (seen as "spontaneous-like" simultaneous rise and decay of T_e,i in two spatial zones) are found for weak ITBs in both RS and NrS plasmas. Profiles of dc_e,i in RS plasmas with strong ITB are usually localized near ITB "foot" inside smaller space region. The maximum of the heat flux variation is located near position of the minimum of safety factor q in various RS plasmas, and variation is extended in positive shear region. Inward and outward heat pulse propagations created by dc_e,i and sawtooth-like crashes are analyzed, small values of c_e,i and absence of "heat pinch" are found in ITB region. Another source of abrupt dc_e,i inside most of plasma volume, including significant part of weak ITB in RS plasmas, is seen as ELM-induced H-L transitions.