Modeling of asymmetric redeposition distribution between inner and outer regions of the W-shaped divertor in JT-60U

Poloidal distributions of erosion depth and deposition thickness on components in the inner and outer regions of the W-shaped divertor in JT-60U are modeled using EDDY. Hydrocarbons released from the outer divertor plate are immediately ionized when entering the plasma and are redeposited near the release position. But they are subjected to re-erosion by the successive bombardment of plasma ions, resulting in small effective sticking. On the whole, most area of the outer divetor plate are eroded agreeing with observed distributions of erosion depth. In contrast, the inner divertor plate is dominated by deposition and the observed poloidal distribution of the thickness of the redeposited carbon layers agrees with incoming carbon flux from the plasma without re-erosion owing to lower-temperature. Due to much lower-temperature (∼1 eV) of the private plasma in the outer region, the neutral carbon/hydrocarbon species are locally redeposited at the bottom edge of the outer dome wing adjacent to the bottom of the outer divertor plate.