Elemental and topographical imaging of microscopic variations in deposition on NSTX-U and DIII-D samples. (January 2019)

• Record Type: Journal Article
• Authors: Skinner, C.H.; Chrobak, C.P.; Jaworski, M.A.; Kaita, R.; Koel, B.E.
• Is Part Of: Nuclear materials and energy. Volume 18(2019)
• Page Start: 35
• Page End: 40
• Publication Date: 2019-01
• Subjects: Erosion -- Deposition -- NSTX-U -- DiMES -- Plasma-materials interaction -- Surface analysis; Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2018.12.001
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: Elemental images show strong microscopic variations in deposition. Topographical maps were compared to the elemental deposition pattern. Deposition is concentrated in areas shadowed from the ion flux. Abstract: Tokamak plasma facing components have surface roughness that can cause microscopic spatial variations in erosion and deposition and hence influence material migration, erosion lifetime, dust and tritium accumulation, and plasma contamination. However, high spatial resolution measurements of deposition on a sub-µm scale of surface roughness have been lacking to date. We will present elemental images of graphite samples from NSTX-U and DIII-D DiMES experiments performed with a Scanning Auger Microprobe at sub-micron resolution that show strong microscopic variations in deposition and correlate this with 3D topographical maps of surface irregularities. The NSTX-U samples were boronized and exposed to deuterium plasmas. The DiMES samples had localized Al and W films and were exposed to dedicated helium plasmas. Topographical maps of the samples were performed with a 3D confocal optical microscope and compared to the elemental deposition pattern. The results revealed localized deposition concentrated in areas shadowed from the ion flux, incident in a direction calculated by taking account of the magnetic sheath.