TY - JOUR
T1 - Initial growth phase of W-fuzz formation in ultra-long pulse helium discharge in LHD
AU - LHD Experiment Group
AU - Tokitani, M.
AU - Masuzaki, S.
AU - Kasahara, H.
AU - Yoshimura, Y.
AU - Sakamoto, R.
AU - Yoshida, N.
AU - Ueda, Y.
AU - Mutoh, T.
AU - Nagata, S.
N1 - Publisher Copyright:
© 2016 Elsevier Ltd
PY - 2017/8
Y1 - 2017/8
N2 - 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.
AB - 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.
KW - Ion beam analysis
KW - LHD
KW - TEM observation
KW - W-fuzz
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U2 - 10.1016/j.nme.2016.11.023
DO - 10.1016/j.nme.2016.11.023
M3 - Article
AN - SCOPUS:85009192353
VL - 12
SP - 1358
EP - 1362
JO - Nuclear Materials and Energy
JF - Nuclear Materials and Energy
SN - 2352-1791
ER -