The world’s first large superconducting fusion experiment, a heliotron-type stellarator at NIFS in Toki, Japan, that operated for 27 years and demonstrated record-breaking long-pulse and high-temperature plasmas.
The Large Helical Device (LHD) was a heliotron/torsatron stellarator operated by the National Institute for Fusion Science (NIFS) in Toki, Gifu Prefecture, Japan. It achieved first plasma on 31 March 1998 and concluded experiments on 25 December 2025 after more than 27 years and over 200,000 plasma shots.[1]
LHD uses two continuous superconducting helical coils winding around the torus, supplemented by six superconducting poloidal coils. Unlike tokamaks, it requires no plasma current for confinement, eliminating disruption risk. It was the world’s first large fusion device to use superconducting coils for plasma confinement.[2]
Ion temperature: 10 keV (~120 million degrees) achieved in the first deuterium campaign (2017), a record for helical/stellarator devices. Both electron and ion temperatures reaching 100 million degrees simultaneously were achieved in FY2020.[3]
Long-pulse record: 54-minute sustained discharge with 1.6 GJ total input energy, achieved in FY2005 — demonstrating the steady-state capability inherent to the stellarator concept.[4]
The first deuterium plasma experiment began 7 March 2017. These experiments demonstrated a clear isotope effect on internal transport barrier formation and produced approximately 6.4 GBq of tritium in the first campaign.
LHD’s experiments concluded in December 2025. NIFS has launched a successor project with a renovated facility (CHD) and experiments planned for FY2026.