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Abstract: 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 16μm for the density of 1.7×103 kg/m3. The highest concentration (19at.%) 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. [Copyright &y& Elsevier]

Abstract: Deuterium depth profiles in graphite tiles of JT-60U have been determined by means of the D(3He,p)4He nuclear reaction. Tiles with net carbon deposition showed high deuterium retention. A D/C ratio of 0.07 was found in the outer dome wing tile. In the inner divertor tile covered with a thick deposition layer, the depth profile shows a broad peak in a deep region. This indicates that deuterium trapped in the shallow region can be replaced by hydrogen with hydrogen discharges due to isotope exchange, while deuterium trapped in the deeper region can not. Deuterium in the redeposited layers can be more easily removed than that in the substrate. The deuterium concentration in the outer divertor target tile was very low (D/C<0.003). The highest D/C ratio, 0.09, was found in the upper region of the first wall. [Copyright &y& Elsevier]

Abstract: Deuterium concentrations and depth profiles in plasma-facing graphite tiles used in the divertor of JAERI Tokamak-60 Upgrade (JT-60U) were investigated by nuclear reaction analysis (NRA). The highest deuterium concentration of D/12C of 0.053 was found in the outer dome wing tile, where the deuterium accumulated probably through the deuterium–carbon co-deposition. In the outer and inner divertor target tiles, the D/12C data were lower than 0.006. Additionally, the maximum (H+D)/12C in the dome top tile was estimated to be 0.023 from the results of NRA and secondary ion mass spectroscopy (SIMS). Orbit following Monte-Carlo (OFMC) simulation showed energetic deuterons caused by neutral beam injections (NBI) were implanted into the dome region with high heat flux. Furthermore, the surface temperature and conditions such as deposition and erosion significantly influenced the accumulation process of deuterium. The deuterium depth profile, scanning electron microscope (SEM) observation and OFMC simulation indicated the deuterium was considered to accumulate through three processes: the deuterium–carbon co-deposition, the implantation of energetic deuterons and the deuterium diffusion into the bulk. [Copyright &y& Elsevier]

It is important to measure retentions and depth profiles of deuterium and tritium on plasma facing materials to understand plasma-wall interactions. The nuclear reaction analysis (NRA) has been established using a deuteron beam with an adjustable energy. By means of the NRA, depth profiles of deuterium and tritium on the surface of JT-60 divertor graphite tiles irradiated with DD burning were obtained. The NRA method showed that the average concentrations of the deuterium retained in the surface of two different were 1.3 × 1016 and 0.3 × 1016 cm-2. α-particles from the T(d, α)n reaction were measured from a dome unit tile of JT-60U W-shaped divertor and the measured activity of tritium was about 18 kBq/cm2. The peak energy of the α spectrum obtained with the NRA was about 1.2 MeV. This result implies that energetic tritons were implanted in the divertor graphite tile. [Copyright &y& Elsevier]

Surface topography and deuterium retention in polycrystalline hot-rolled W and W–5%Re have been examined after exposure to a low-energy (76 eV), high flux (around 10 22 D/m 2 s) deuterium plasma to an ion fluence of 10 26 D/m 2 at various temperatures. The methods used were confocal laser scanning microscopy and the D( 3 He, p) 4 He nuclear reaction at 3 He energies varied from 0.69 to 4.0 MeV. During exposure to the D plasma at temperatures in the range from 348 to 673 K, small blisters of size in the range from about 1 to about 15 μm, depending on the exposure temperature, are formed on the W and W–5%Re surfaces. In the W–5%Re, the deuterium retention demonstrates its maximum at exposure temperature of 463 K, while in the W this maximum is shifted to 523 K. A difference in the temperature dependence of the D retention for the W and W–5%Re is explained, as a rough approximation, by temperature dependences of the ductility of these materials. [ABSTRACT FROM AUTHOR]

Low-Z impurity (7Be) on the JT-60U divertor tiles was analyzed to study the impurity behavior in the divertor region. The amount of the 7Be increased approximately one hundred times after B4C-tile installation in the outer divertor. The 7Be was probably produced by 10B(p,α)7Be nuclear reaction on the divertor tiles in the hydrogen experiment with ion cyclotron range of frequency heating. The 7Be was distributed asymmetrically in the poloidal and the toroidal direction. The highest 7Be concentration was found at the inner divertor whose boron content (B/(B+C) ∼ 20%) was lower than the B4C tiles (B/(B+C) ∼ 80%) of the outer divertor. This result may imply impurity transport from the outer divertor to the inner divertor. [Copyright &y& Elsevier]

Abstract: Retention and depth profile of all hydrogen isotopes (hydrogen, deuterium and tritium) in the carbon tiles of outer divertor, outboard baffle plate and outboard first wall in JT-60U, which were mostly eroded, were measured by TDS, SIMS and TIPT, and discussed from view points of tile temperature, incident energy and flux of impinging H, D and T. The distribution of T in the analyzed tiles was compared with the impinging flux of tritium produced by DD reactions, which was calculated by the OFMC code. In this paper, H, D and T retention mechanisms and isotopic replacement effects are summarized. [Copyright &y& Elsevier]