Japan’s seven-decade fusion effort — from early stellarator work to JT-60, LHD, JT-60SA, and a leading role in ITER — making it one of the world’s most advanced and sustained national fusion programs.
ReviewedLast reviewed: 9 Aug 2026·Category: History & Milestones
Origins
Japan began fusion research in the late 1950s at universities and the Japan Atomic Energy Research Institute (JAERI). Early work included stellarators and mirrors, but by the 1970s the program focused on tokamaks, culminating in the construction of JT-60 at JAERI’s Naka Fusion Institute.[1]
JT-60 and JT-60U
JT-60U (1991–2008) achieved the world’s highest fusion triple product (1.5×1021 keV·s/m³) in 1998, surpassing JET and TFTR. It demonstrated reversed-shear plasmas, long-pulse operation, and advanced tokamak scenarios that directly inform ITER operations.
LHD
The Large Helical Device at the National Institute for Fusion Science (NIFS) in Toki has operated since 1998 as the world’s largest heliotron-type stellarator (R = 3.9 m), achieving ion temperatures of 10 keV and demonstrating long-pulse plasma sustainment up to 48 minutes.[2]
JT-60SA and ITER
JT-60SA (Super Advanced), a joint EU–Japan project, achieved first plasma in October 2023 as the world’s largest superconducting tokamak. Japan hosts the ITER Broader Approach activities and contributes critical ITER components including superconducting coils, neutral beam systems, and the blanket remote handling system.[3]
Sources
Ninomiya, H. et al. "JT-60U results and their implications for ITER." Fusion Science and Technology, 42, 7–28, 2002.
Motojima, O. et al. "Extended steady-state and high-beta regimes of net-current free heliotron plasmas in the Large Helical Device." Nuclear Fusion, 47, S668, 2007.
Shirai, H. et al. "JT-60SA: overview of the project and its progress." Nuclear Fusion, 57, 102002, 2017.