Large Helical Device
Large Helical Device is a stellarator fusion device run by National Institute for Fusion Science in Japan. It is operating. Like every fusion device built so far, it has produced no net electricity.
Sustained discharges of more than 47 minutes, far longer than any tokamak, which follows from the design: a stellarator confines plasma with external coils alone and needs no driven plasma current, so there is nothing that has to be continually re-established.
The largest superconducting stellarator until Wendelstein 7-X and still one of only two at that scale. Its duration results are the clearest demonstration of the stellarator's structural advantage over the tokamak, and of why the tokamak nevertheless leads on plasma performance.
| Organisation | National Institute for Fusion Science |
|---|---|
| Approach | stellarator |
| Confinement | magnetic |
| Country | Japan |
| Status | Operating |
| First plasma | 1998 |
| Target date | none stated |
|---|---|
| Power target | none stated |
| Energy gain target | none stated |
| Net electricity | No. no fusion device has produced any |
Other stellarator projects
| Project | Status |
|---|---|
| Infinity Two | Planned |
| Wendelstein 7-X |
Fusion needs tritium, and the world's civilian stock comes mostly from CANDU fission reactors. See the fusion overview.
Large Helical Device in context
3 of the 24 fusion projects on record use the stellarator approach: 2 operating, 0 under construction, 1 planned.
Its first plasma is dated 1998, 28 years ago: the 3rd earliest of 15 projects on record with a first-plasma date.
| Measure | Large Helical Device | Median of all projects | Standing |
|---|---|---|---|
| First plasma | 1998 | 2015 | 3 of 15 (earliest first) |
Worked out from the entries on this site only, so a figure compares Large Helical Device with what is recorded here, not with everything that exists. An entry with no value for a measure is left out of that measure's ranking and median.
Sources
- International Atomic Energy Agency, Overview of LHD experiments · retrieved 2026-09-07
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data