JT-60SA is a major international tokamak project in Naka, Japan, combining Japanese and European leadership with U.S. diagnostics expertise from Princeton. The device will use superconducting magnets to confine superhot plasma and will host a four-ton X-ray imaging crystal spectrometer to improve plasma measurements. JT-60SA aims to explore new plasma regimes and inform future fusion power designs; however, fusion remains experimental while solar power continues to be cheaper and faster to deploy.
Inside JT-60SA: The Tokamak Aiming to Recreate Sunlike Fusion, with U.S. Diagnostics Support
JT-60SA is a major international tokamak project in Naka, Japan, combining Japanese and European leadership with U.S. diagnostics expertise from Princeton. The device will use superconducting magnets to confine superhot plasma and will host a four-ton X-ray imaging crystal spectrometer to improve plasma measurements. JT-60SA aims to explore new plasma regimes and inform future fusion power designs; however, fusion remains experimental while solar power continues to be cheaper and faster to deploy.
01:54 PM, 11/19/2025Science
International effort builds a powerful new tokamak
An international consortium led by Japan and Europe is building JT-60SA, a large tokamak in Naka, Japan, designed to reproduce the high-temperature, high-pressure conditions that power the sun. The project combines Japanese engineering and European coordination with technical diagnostics support from the U.S. Princeton Plasma Physics Laboratory (PPL).
What JT-60SA will do
JT-60SA will use powerful magnetic fields and continuously operating superconducting magnets to confine superheated plasma long enough to study fusion-relevant physics. By accessing operating regimes not previously achieved, the machine will test new plasma behaviors and concepts that could inform the design of future fusion power plants.
“This calibration scheme has never been implemented before at this scale,” said Luis Delgado-Aparicio, head of advanced projects at PPL.
Key diagnostics: an X-ray imaging crystal spectrometer
One notable contribution from PPL is a four-ton X-ray imaging crystal spectrometer that will give researchers more precise measurements of plasma temperature, composition, and radiation. Improved diagnostics are essential to understanding and controlling the plasma needed for sustained fusion reactions; the spectrometer is scheduled for installation next year.
How fusion differs from fission
Fusion joins atomic nuclei to form heavier atoms, releasing energy in the process. This contrasts with fission, which splits atoms apart. Fusion’s potential advantages include minimal long-lived radioactive waste and a negligible risk of large-scale meltdowns that have historically concerned the public with some fission reactors. Both fusion and fission produce low direct greenhouse-gas emissions compared with fossil fuels.
Context and what comes next
Until larger projects such as ITER in France are fully operational, JT-60SA will be among the most powerful tokamaks in service and an important testbed for technologies needed on the path to commercial fusion power. Worldwide efforts also include alternative approaches to lower the extreme temperatures required for fusion and other large tokamak initiatives under development.
Near-term energy realities
While fusion remains experimental and years away from commercial electricity generation, near-term energy solutions such as solar power are currently cheaper and faster to deploy. Governments and utilities weigh both immediate clean-energy deployments and long-term investments in advanced technologies like fusion when planning future energy systems.
Bottom line: JT-60SA represents a crucial international step toward understanding and harnessing fusion. Improved diagnostics and new operating regimes will provide data that could accelerate the development of future fusion power plants, even as practical deployment remains a medium- to long-term goal.