Deuterium depth profiling in graphite tiles not exposed to hydrogen discharges before air ventilation of JT-60U

Depth profiles of deuterium trapped in graphite tiles not exposed to hydrogen discharges just before air ventilation of JT-60U were determined based on the D(3He,p)4He resonant nuclear reaction analysis. The samples were taken from the W-shaped divertor. The maximum depth of analysis is about 1.4 × 1024 carbon atoms/m2, corresponding to a linear depth of 16 μm for the density of 1.7 × 103 kg/m3. The highest concentration (19 at.%) was found at the surface of the inner divertor area, which was significantly higher than that exposed to H discharges at the same location. However in the deeper region, the deuterium concentrations without H discharges were lower than those with H discharges in 3 of 4 samples. These results indicate that hydrogen discharges can remove deuterium trapped only in the shallow region.