Abstract Three bolometer arrays, an IR television camera, a photodiode array, spectrometers, a Langmuir probe array, Penning gauges and quadrupole mass analyzers were installed for divertor diagnostics to study the divertor physics in the JT-60U tokamak. The radiative cooling divertor was investigated to reduce the heat load on the divertor plates using these diagnostics. The mechanism of radiation losses was spectroscopically studied by visible spectroscopy. The heat and particle fluxes were measured with fast sampling during the ELMy H-mode. Carbon generation can be modelled very well. Helium exhaust from the core plasma was observed as a result of wall pumping caused by solid target boronization.