Localized tungsten deposition in divertor region in JT-60U

Abstract

Tungsten local transport in the diverter region emitted from the outer divertor was studied in JT-60U. Tungsten-coated CFC tiles were installed in the outer divertor position, on which outer strike points did not normally sit. A neutron activation method to measure tungsten surface density was used for the first time. On the outer wing tile, W existed only in the top surface, while on the inner divertor tile W was embedded in the thick carbon deposition layer. Poloidal distribution in the same toroidal section as the tungsten tiles showed dense W deposition near the inner strike points, the dome top and outer wing of the dome. Carbon ions by puffing 13CH4 at the same toroidal position of the W-tiles were also deposited near the inner strike points. Toroidal distribution on the outer wing showed significant localization of W deposition near the W tile array. In addition, toroidal asymmetry of W deposition on the outer wing probably due to the plasma parallel flow was observed.