Hydrogen Retention and Impurity Deposition of JT–60 Graphite Divertor tiles

For the graphite tiles used as divertor plate in lower × point configuration of JT-60, the spatial and depth profiles of retained hydrogen and impurities were measured by means of MeV range ion beam analysis techniques. The hydrogen concentration in the depth less than 50 nm was as high as 20%. The hydrogen concentration decreased with the depth. A considerable amount of hydrogen was observed in the deeper region up to ˜2 millimeters. The dominant impurity species were Ni, Cr, Ti, Fe, Mo and Nb. Small amount of Al, Si, K and Ca were also detected. Most dominant species was Ni, and the concentration was as high as 10 18 /cm 2 . The total metal impurity concentration was estimated as several percents. In the off-trace region, the spatial distribution of impurity was considerably uniform. However, in the divertor trace regions, large variation of the spatial distribution was observed.