Deuterium retention in deposited W layer exposed to EAST deuterium plasma. (August 2017)

• Record Type: Journal Article
• Authors: Katayama, K.; Ashikawa, N.; Ding, F.; Mao, H.; Zhou, H.S.; Luo, G.N.; Wu, J.; Noguchi, M.; Fukada, S.
• Is Part Of: Nuclear materials and energy. Volume 12(2017)
• Page Start: 617
• Page End: 621
• Publication Date: 2017-08
• Subjects: Deuterium retention -- Deposited tungsten -- EAST; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2017.04.004
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: The deposited W layer was formed by hydrogen plasma sputtering. The deposited W layer were exposed to EAST deuterium plasma. A deuterium release was clearly observed from the deposited W layer exposed to EAST deuterium plasma. Deuterium release peaks from the deposited W layer were close to that from the W layer irradiated by deuterium ions at 573 K. Retained deuterium in the deposited W had a peak at about 50 nm Abstract: The deposited W layers formed on the W plate by hydrogen plasma sputtering were exposed to deuterium plasma in EAST together with bare W plate. In TDS measurement, the deuterium release was clearly observed from the deposited W layer in addition to the release of hydrogen which was incorporated during the sputtering-deposition processes. On the other hand, the release of hydrogen isotope was not detected from the bare W plate. This suggests that the formation of deposited W layers increases tritium inventory in the plasma confinement vessel. Although the thermocouple contacting to the backside of the W plate did not indicate a remarkable temperature rise, deuterium release peaks from the W layer were close to that from the W layer irradiated by 2 keV D2 + at 573 K. It was found by glow discharge optical emission spectrometry analysis that retained deuterium in the W layer has a peak at the depth of 50 nm and gradually decreases toward the W substrate. From X-ray photoelectron spectroscopy analysis, it was evaluated that W oxide existed just at the surface and W atoms in the bulk of deposited W layer were not oxidized. These data suggest that hydrogen isotopes are not retained in W oxide but grain boundaries.