Co-deposited layers on gap surfaces of bulk tungsten divertor tiles in JET ITER-like wall: Directional effects and nanostructures

Masayuki Tokitani, Mitsutaka Miyamoto, Suguru Masuzaki, Yuji Hatano, Sun Eui Lee, Yasuhisa Oya, Hironori Kurotaki, Nobuyuki Asakura, Hirofumi Nakamura, Takumi Hayashi, Marek Rubel, Anna Widdowson, Jari Likonen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Co-deposited layers on surfaces of bulk tungsten divertor tiles (W lamellae) from the first campaign of JET with the ITER-Like Wall (JET-ILW, 2011–2012) were examined by means of a cross-sectional transmission electron microscope observation. The focus was on geometrical effects in impurity deposition, mainly beryllium (Be), on surfaces located in the poloidal gap separating adjacent lamellae. The study was carried out on the sides (gap surfaces) of two W lamellae from Stack C (located on the outboard part of the horizontal section of the lower divertor), from the region most exposed to the plasma (lamella C23) and in the magnetic shadow of the upstream divertor module (lamella C3). The tile manufacturing process (cold rolling) left shallow grooves, i.e. structures classified as convex (hill) and concave (valley) regions. These regions are decisive for the deposition structure. The main results were: (i) two kinds of impurity deposition features, “homogeneous” and “directional”, have been distinguished; (ii) the directional ones were characterized by nanoscale inclined vertical stripes in the deposition layer; (iii) homogeneous deposition without directional features were in the valley region. The results clearly indicate the impact of the surface finish, even in the tile gaps, on the qualitative and quantitative aspects of deposition.
Original languageEnglish
Article number101678
Pages (from-to)101678
JournalNuclear Materials and Energy
Volume39
DOIs
Publication statusPublished - 2024
MoE publication typeA1 Journal article-refereed

Keywords

  • Dust
  • Fuel retention
  • Tungsten divertor
  • Deposition layer

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