Initial growth phase of W-fuzz formation in ultra-long pulse helium discharge in LHD

LHD Experiment Group

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

In order to confirm the formation of a tungsten fiberform nanostructure (W-fuzz) by helium plasma exposure in the large-sized plasma confinement device, the bulk tungsten with the size of 80 × 20 × 1.5 mm3 was inserted into the divertor leg position in the Large Helical Device (LHD). Then, it was exposed to the divertor plasma during the ultra-long pulse helium discharges with 10,190 s in total. The width of the divertor plasma, incident ion energy and total fluence were expected to be ∼2 cm, 100–200 eV and ∼5 × 1025 He/m2 (strike position), respectively. The surface temperature of the tungsten specimen was monitored by IR camera. The typical surface temperature of the divertor strike point was estimated to be around 1900 ∼ 2300 K. After the exposure, an initial growth phase of tungsten fiberform nanostructure (W-fuzz) was able to be identified on the tungsten surface. The finest initial growth phase of the W-fuzz structure was able to be identified on the central region of the divertor strike point, where retention amount of helium was estimated to be ∼8 × 1021 He/m2. This study is the first simultaneous evaluation of the W-fuzz growth and quantification of the helium retention in the large-sized plasma confinement device.

Original languageEnglish
Pages (from-to)1358-1362
Number of pages5
JournalNuclear Materials and Energy
Volume12
DOIs
Publication statusPublished - 2017 Aug

Keywords

  • Ion beam analysis
  • LHD
  • TEM observation
  • W-fuzz

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Materials Science (miscellaneous)
  • Nuclear Energy and Engineering

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