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Effects of Helium Ions on Hydrogen Isotope Behavior in Tungsten

Y. Ueda, H. Kashiwagi, M. Fukumoto, Y. Ohtsuka, N. Yoshida

Fusion Science and Technology / Volume 56 / Number 1 / July 2009 / Pages 85-90

Divertor and High Heat Flux Components / Eighteenth Topical Meeting on the Technology of Fusion Energy (Part 1) /

Simultaneous irradiation effects of He on tungsten blistering with hydrogen and carbon mixed ion beam were investigated. It was found that only 0.1% addition of He ions to 1 keV H and C mixed ion beam (C:0.8-1.0%) reduced (at 473 K) or completely suppressed (at 653 K and 723 K) blister formation. In order to obtain more detailed result, two ion sources were used to irradiate tungsten with H and He ions with different energies. In the He energy of 0.6 keV (1.5 keV H&C),significant blistering was observed, while in the He energies of 1.0 keV and 1.5 keV, blister formation was suppressed. These results suggested that a He bubble layer reduced hydrogen diffusion through the layer. A He bubble size and a volume rate were about 1-2 nm and ~2% at 653 K, respectively. To evaluate T retention in the ITER tungsten wall, this effect should be included.

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