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

Hayashi, Takao; Sugiyama, Kazuyoshi*; Mayer, M.*; Krieger, K.*; Masaki, Kei; Tanabe, Tetsuo*; Sato, Masayasu

Absolute concentrations and the depth profiles of D in plasma-facing graphite tiles used in JT-60U were determined by means of the D(He, p)He resonant nuclear reaction. The analyzed samples were not exposed to H discharges before air ventilation. The maximum depth of analysis is about 1.4 10 carbon (C) atoms/m, corresponding to a linear depth of 16 m for the density of 1.7 10 kg/m. The highest D concentration was found at the inboard mid-plane of first wall area. The maximum D concentration is D/C=0.13, and the concentration decrease with the depth. The D retention within 16 m is 1.9 10 D atoms/m. The D retentions in this paper were about 29 times larger than previous samples, which were located on the same area and exposed to the hydrogen discharges. This indicates the H plasma discharges were effective to remove the D (and T) from graphite tiles in the first wall area.