Large Helical Device

The Large Helical Device is a superconducting stellarator at Japan’s National Institute for Fusion Science. It confines plasma in a helical magnetic field to study fusion-relevant conditions.

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Stellarator: A magnetic-confinement fusion device whose twisted magnetic field is produced mainly by external coils. The Large Helical Device is a major superconducting example of this confinement design.
Fusion energy: Energy released by nuclear fusion, the joining of light atomic nuclei. The device studies plasma conditions that could inform practical fusion energy.
National Institute for Fusion Science: A Japanese research institute devoted to plasma science and fusion research. The institute operates the Large Helical Device in Toki, Gifu Prefecture.
Tokamak: A toroidal fusion device that combines external magnetic fields with plasma current for confinement. Unlike a tokamak, the device obtains most of its rotational transform from external helical coils.
Heliotron: A stellarator configuration that uses continuous helical coils to generate rotational transform. The device’s defining helical coils embody this stellarator configuration.
Nuclear fusion: A nuclear reaction in which light nuclei combine into heavier nuclei and release energy. Fusion reactions motivate the high-temperature plasma conditions investigated in the device.
Toki, Gifu: A city in Gifu Prefecture, Japan, that hosts the National Institute for Fusion Science. The device is located at the institute’s Toki campus.
ITER: An international tokamak project under construction in France to demonstrate burning plasma science. Its tokamak strategy contrasts with the device’s stellarator approach to steady-state confinement.
Magnetic confinement fusion: A fusion approach that uses magnetic fields to keep hot plasma away from material walls. The device is built to investigate this broader confinement approach.
Helical-axis heliotron: A heliotron configuration in which the magnetic axis itself follows a helical path. Experiments in the device explore this configuration’s confinement properties.