High-beta steady-state research and future directions on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade and the Japan Atomic Energy Research Institute Fusion Torus-2 Modified

In the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U), a high- β p ELMy H-mode (high-poloidal-beta high-confinement-mode with edge localized mode) plasma was sustained with β N ∼2.7 for 7.4 s. Real-time neoclassical tearing mode (NTM) stabilization system was established and effective NTM suppression by early electron cyclotron (EC) wave injection was demonstrated. High fusion triple product of n i (0)τ E T i (0)=3.1×10 20 keV⋅s⋅m −3 was achieved using the negative-ion based neutral beam current drive with β N ∼2.5 and the bootstrap current fraction f BS ∼50%. In a hot electron regime, a high electron cyclotron current drive efficiency of 4.2×10 18 A/W/m 2 was achieved at T e ∼21  keV . Innovative current start-up scenario produced a current hole plasma with a very high f BS ∼90%. No accumulation of helium and carbon impurities was observed for internal transport barrier (ITB) plasmas. While argon impurity was accumulated, EC injection effectively exhausted it across ITB. In a regi...