AbstractA YAG laser Thosmon scattering system for JT-60U has been developed to measure the pseudo-continuous time evolution of electron temperature and density profiles with 20 spatial channels. The target parameter ranges are 20 eV–20 keV for electron temperature and 5 × 1018 m−3−2 × 1020 m-3 for electron density. The system consists of a Nd-YAG laser (1064 urn, 2 J, 10 Hz) and 20 polychromators with six spectral channels equipped with thermostabilized silicon avalanche photodiode detectors. The design, results and future plans are presented.