Isolated nano-tendril bundles on tungsten surfaces exposed to radiofrequency helium plasma. (August 2017)

• Record Type: Journal Article
• Authors: Woller, Kevin B.; Whyte, Dennis G.; Wright, Graham M.
• Is Part Of: Nuclear materials and energy. Volume 12(2017)
• Page Start: 1282
• Page End: 1287
• Publication Date: 2017-08
• Subjects: Tungsten fuzz -- Helium -- Nano-tendril -- RF sheath; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2017.04.016
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: Modulation of incident ion energy at a frequency of 13.56 MHz affects the resulting surface morphology of tungsten during exposure to helium plasma. Nano-tendril bundles and unsupported whiskers are observed with <10% coverage of the surface. Isolated structures provide critical evidence of alternative surface modification over W fuzz in RF environments. Abstract: The DIONISOS experiment is used to study the impact of RF helium (He) plasma on the surface morphology of tungsten (W) at a frequency of 13.56 MHz. Helium ion energy distributions with a span of 70–75 eV, while still below the sputtering threshold result in nano-tendril bundles (NTBs) and free-standing W whiskers on surfaces at 1020 K. The NTBs are distributed intragranularly with coverage of less than 10% while reaching up to 30 µm normal to the surface for He ion fluence of 7.6 × 10 25 m −2 and flux density of 10 22 m −2 s −1 . Analysis of the NTB interior and sub-surface structure is provided through focused ion beam cross section.