Motion of W and He atoms during formation of W fuzz

Journal Article · Wed Apr 11 00:00:00 UTC 2018 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/aab96a · OSTI ID:1435242

Doerner, R. P. ^[1]; Nishijima, D. ^[1]; Krasheninnikov, S. I. ^[1]; Schwarz-Selinger, T. ^[2]; Zach, M. ^[3]

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1. Univ. of California, San Diego, CA (United States). Center for Energy Research
2. Max-Planck Inst. fur Plasmaphysik, Garching, (Germany)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division

Measurements are conducted to identify the motion of tungsten and helium atoms during the formation of tungsten fuzz. In a first series of experiments the mobility of helium within the growing fuzz was measured by adding ³He to the different stages of plasma exposure under conditions that promoted tungsten fuzz growth. Ion beam analysis was used to quantify the amount of ³He remaining in the samples following the plasma exposure. The results indicate that the retention of helium in bubbles within tungsten is a dynamic process with direct implantation rather than diffusion into the bubbles, best describing the motion of the helium atoms. In the second experiment, an isotopically enriched layer of tungsten (~92.99% ¹⁸²W) is deposited on the surface of a bulk tungsten sample with the natural abundance of the isotopes. This sample is then exposed to helium plasma at the conditions necessary to support the formation of tungsten 'fuzz'. Depth profiles of the concentration of each of the tungsten isotopes are obtained using secondary ion mass spectrometry (SIMS) before and after the plasma exposure. The depth profiles clearly show mixing of tungsten atoms from the bulk sample toward the surface of the fuzz. Lastly, this supports a physical picture of the dynamic behavior of helium bubbles which, also, causes an enhanced mixing of tungsten atoms.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: European Union (EU); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Grant/Contract Number: AC05-00OR22725; FG02-07ER54912; SC0018302
• OSTI ID: 1435242
• Journal Information: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 6 Vol. 58; ISSN 0029-5515
• Publisher: IOP ScienceCopyright Statement
• Country of Publication: United States
• Language: English