HomeLHD Achievements

Plasma parameters The core plasma of a future fusion reactor must have an ion temperature of more than 120 million degrees Celsius and a density of more than 100 trillion ions per cm3 at the same time for sustained fusion reactions of deuterium and tritium as fuel. The LHD has been improving its plasma performance for 20 years since the first plasma ignition on March 31, 1998, using hydrogen. The ion temperature reached 120 million degrees in the deuterium experiment that started in March 2017, with a central density of 13 trillion ions per cm3. In terms of density, we achieved a central density of 1200 trillion per cm3, which is more than 10 times the requirement for fusion, at a low temperature of 3 million degrees. In addition, the β value (the ratio of plasma pressure to magnetic field pressure), which determines the economic efficiency of a fusion reactor, was successfully increased to more than 5 % for the first time in the world for a helical system. The table below shows the achieved values of the plasma parameters obtained so far in LHD. Detailed experimental data analysis using advanced plasma measurement devices developed in LHD and theoretical studies using computer simulations are being conducted in collaboration with universities and research institutes in Japan and overseas. In addition, theoretical studies using computer simulations are being conducted in collaboration with universities and research institutes in Japan and overseas.
Plasma parametersAchievementFinal goal
 Ion temperature120 million degrees
(1.3×1019 /m3
120 million degrees
(2.0×1019 /m3
 Electron temperature230 million degrees
(0.2×1019 /m3
120 million degrees
(1.6×1019 /m3
120 million degrees
(2.0×1019 /m3
 Electron density1.2×1021 /m3
(3 million degrees)
4.0×1020 /m3
(15 million degrees)
 β value5.1 %
(0.425 T)
4.1 %
(1.00 T)
5 %
(1-2 T)
 Plasma duration54 min.(0.5 MW)
48 min.(1.2 MW)
1 hour(3 MW)