Hydrogen isotope retention and impurity deposition of carbon based components used in JT-60U

Abstract

Various types of carbon based components, such as isotropic graphite, carbon fiber composite (CFC-2D felt type) and B 4C-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 ∼ 6 × 10 20 and ∼ 6 × 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 B 4C converted graphite tile. Carbon tile containing B 4C is shown to be useful for oxygen gettering compared with an other.