Recent results from high performance and steady-state researches in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade

Abstract

High IP hot ion high confinement (H) mode at IP up to 4.5 MA has been exploited. Sawtooth stabilization by ion cyclotron range of frequencies (ICRF) heating is effective to improve performance in this regime. The performance is limited by the onset of giant edge localized modes (ELMs). It was found that the edge pressure gradient at the onset of ELMs can be increased with increasing triangularity δ up to 0.4 at IP<1.2 MA. The normalized beta (βN) value at the ELM onset also increases from ∼1 to ∼2.8 when δ is increased from ∼0.1 to ∼0.33, respectively. In the reversed-shear operation, an internal transport barrier (ITB) appears, not only for the ions but also for the electrons. The improved confinement region is quite large (within r/a∼0.65). The highest confinement enhancement factor (H factor) and βN achieved so far are, respectively, 2.6 and 2.4 for reversed-shear plasmas. A scaling law of the H-mode threshold power, which is consistent with the International Thermonuclear Experimental Reactor (ITER) [Y. Shimomura, Phys. Plasmas 1, 1612 (1994)] scaling, is derived. The power threshold for ITB formation in the high βp mode depends on the electron density, but not on the toroidal field. It is validated that the control of the toroidal rotation is effective to control toroidicity-induced Alfvén eigenmodes (TAE modes).