HYDROGEN ISOTOPE RETENTION AND IMPURITY DEPOSITION OF CARBON-BASED COMPONENTS USED IN JT-60U

Various types of carbon based components, such as isotropic graphite, carbon fiber composite (CFC-2D felt type) and B4C-overlaid CFC/graphite were used for divertor and first wall tiles in JT-60U. Surface analysis of tiles exposed to discharge shots in JT-60U, was performed using MeV region ion beam. The retention of deuterium for each tile was distributed between similar to 6 x 10(20) and similar to 6 x 10(21) m(-2). Highest deuterium retention was observed on the outboard, lower part of first wall tiles. Metallic impurity measurement was performed by X-PIXE. The dominant species were Fe, Cr, Ni, Cu, Mo and Zn of which total concentration as high as 10(21) m(-2). This value is one order of magnitude smaller than that of JT-60. Highest oxygen concentration examined by RBS was observed on the B4C converted graphite tile. Carbon tile containing B4C is shown to be useful for oxygen gettering compared with an other.