The international collaboration supporting the JT-60SA tokamak project, implemented under the Broader Approach Agreement between Euratom and Japan, is celebrating the successful completion of the procurement and delivery of the Divertor Vacuum Ultra Violet (DivVUV) spectrometer system in Naka, Japan. This innovative diagnostic tool, is essential for monitoring plasma impurities and studying the physics of the divertor, that is the region where the plasma meets the containing structures. The instrument has arrived at the Naka site and is now undergoing installation and initial commissioning phases.
The delivery of this complex instrument is the culmination of a multi-year effort involving several research institutions, members of the EUROfusion consortium. Spectrometer vessel has been refurbished and upgrade form a double spectrometer previously used on Textor. New high resolution toroidal gratings were designed in Forschungszentrum Jülich, Germany, the mechanical structure at ICSI, Romania, the vacuum hardware and CCD detector cameras procured by IPPLM in Poland. The overall design, and in particular the optical imaging system has been developed in CRFX, Italy. Once operational, the Divertor VUV system will provide 1D imaging of the divertor region, allowing researchers to resolve radiation from the inner leg, outer leg, and X-point in two spectral ranges, 10–48 nm and 44–125 nm respectively. By tracking emissions from intrinsic impurities like Carbon and Oxygen, as well as seeded gases like Neon and Argon, the diagnostic will be vital for mastering power exhaust and investigating plasma detachment in the divertor region —a key requirement for future fusion reactors like ITER and DEMO.
Final assembly and system integration took place at ENEA Frascati in Italy, where the system underwent a rigorous acceptance test in December 2025 in presence of
representatives from QST and Fusion for Energy (F4E), the two implementing agencies of JT-60SA. Installation on the upper port of sector 12 is currently underway. The DivVUV will see its first JT-60SA plasma light during the incoming operation phase 2.
