PPPL has delivered a four‑ton X‑ray imaging crystal spectrometer to Japan's JT‑60SA tokamak, strengthening the facility's real‑time plasma diagnostics. The instrument will measure temperature, density and composition, helping researchers maintain magnetic confinement and explore new operating regimes. Data from JT‑60SA will inform ITER's design and operations as the international community advances toward net‑positive fusion energy.
U.S. Lab Delivers Four‑Ton X‑Ray Spectrometer to World's Most Powerful Tokamak — A Boost for Fusion Research
PPPL has delivered a four‑ton X‑ray imaging crystal spectrometer to Japan's JT‑60SA tokamak, strengthening the facility's real‑time plasma diagnostics. The instrument will measure temperature, density and composition, helping researchers maintain magnetic confinement and explore new operating regimes. Data from JT‑60SA will inform ITER's design and operations as the international community advances toward net‑positive fusion energy.
12:45 PM, 11/19/2025Science
The Princeton Plasma Physics Laboratory (PPPL), part of the U.S. Department of Energy, has delivered a four‑ton X‑ray imaging crystal spectrometer to Japan's JT‑60SA tokamak in Naka. The instrument is among the United States' first hardware contributions to the facility and will strengthen diagnostics for advanced fusion experiments.
Fusion — the same process that powers the sun — merges light atomic nuclei at extreme temperatures to release large amounts of energy with minimal carbon emissions. Fusion reactions produce little long‑lived radioactive waste, which is why many scientists consider fusion a promising path to long‑term sustainable energy.
The X‑ray imaging crystal spectrometer (XICS) records X‑rays emitted by the superheated plasma and delivers real‑time measurements of temperature, density and composition. Those diagnostics are essential for monitoring plasma behavior and maintaining the magnetic confinement that keeps the plasma from touching reactor walls — one of fusion's most difficult engineering challenges.
"Because JT‑60SA will be such a powerful machine, we will access operating conditions that we have never achieved before," said PPPL scientist Luis Delgado‑Aparicio, who leads advanced projects at the lab. "The measurements need to be very accurate for us to learn the science of these new regimes." PPPL physicist Masayuki Ono added, "XICS is essential — you need something like it to get the data from plasma and do the physics."
Located in Naka, Japan, JT‑60SA is currently the most powerful operating tokamak and is a collaboration between Japan and Europe's Fusion for Energy program. When JT‑60SA becomes fully operational, expected next year, its experimental results will help refine the design and operational strategies for ITER, the large international fusion experiment under construction in France.
By improving diagnostic precision and enabling studies of previously inaccessible plasma regimes, the spectrometer will help researchers test confinement strategies and optimize plasma performance. Wider deployment of fusion technology could diversify low‑carbon energy sources, reduce dependence on fossil fuels, and make future power systems more resilient.
Why this matters
High‑quality diagnostics like the XICS enable tighter control over the plasma and faster learning cycles for fusion experiments. That accelerates progress toward demonstrating net energy gain — a critical milestone for making fusion a practical power source.