Hydrogen isotopes retention in JT-60U

Poloidal/toroidal distributions of hydrogen isotopes (H, D) retention on the plasma facing surfaces and side surfaces of carbon tiles used in JT-60U were investigated. The retention of hydrogen isotopes is nearly proportional to the thickness of carbon redeposited layers. The redeposited layers on the inner divertor area retain hydrogen isotopes uniformly with the concentration of ∼0.02 in (H + D)/C, while those on the tile sides shadowed from the plasma ∼0.13 in (H + D)/C. Total hydrogen isotopes retention in the whole divertor area including the baffle plates and dome unit tiles of JT-60U is estimated to be ∼4 × 1024 atoms assuming that the amount of retained hydrogen isotopes is proportional to the integrated discharge time. Some of the first wall tiles are found to retain significantly large amount of deuterium, which is attributed to the injection of energetic deuterium originating from NBI.