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Hydrogen retention and carbon deposition in plasma facing components and the shadowed area of JT-60U

2007; IOP Publishing; Volume: 47; Issue: 11 Linguagem: Inglês

10.1088/0029-5515/47/11/020

1741-4326

K. Masaki, T. Tanabe, Yuko HIROHATA, Yasuhisa Oya, T. Shibahara, T. Hayashi, K. Sugiyama, Takashi Arai, Kenji Okuno, N. Miya,

Superconducting Materials and Applications

In JT-60U, erosion/deposition analyses of the plasma facing wall have shown that local carbon transport in the inboard direction was appreciable in addition to long-range transport. The total deposition and erosion rates in the divertor region were ~1 × 1021 C atoms s−1 and ~−6 × 1020 C atoms s−1, respectively. About 40% of the deposition in the divertor region likely originates from the main chamber wall. At the plasma facing surfaces of the divertor region, the highest hydrogen concentration in the (H + D)/C ratio and the retention amount were found to be ~0.13 and ~1 × 1023 atoms m−2, respectively. In the plasma-shadowed area underneath the divertor region with a vacuum vessel baking temperature of 420 K, redeposited layers of ~2 µm thickness were found with a high hydrogen concentration of ~0.75 in (H + D)/C, which was nearly the same level as that observed in JET. Large deuterium retention was also observed at the main chamber wall covered with boron layers. Their H + D retention and (H + D)/C were ~1 × 1023 atoms m−2 and ~0.16, respectively, for the vacuum vessel temperature of 570 K. Such a high deuterium retention is most likely caused by D retained in the boron layers. Nevertheless, the integration of this retention over the whole main chamber wall results in significant inventory and needs further investigation.