He-ion and self-atom induced damage and surface-morphology changes of a hot W target
2014; IOP Publishing; Volume: T159; Linguagem: Inglês
10.1088/0031-8949/2014/t159/014029
ISSN1402-4896
AutoresF. W. Meyer, Hussein Hijazi, M. E. Bannister, Predrag Krstić, Jonny Dadras, Harry M. Meyer, Chad M. Parish,
Tópico(s)Metal and Thin Film Mechanics
ResumoWe report results of measurements on the evolution of the surface morphology of a hot tungsten surface due to impacting low-energy (80–12 000 eV) He ions and of simulations of damage caused by cumulative bombardment of 1 and 10 keV W self-atoms. The measurements were performed at the ORNL Multicharged Ion Research Facility, while the simulations were done at the Kraken supercomputing facility of the University of Tennessee. At 1 keV, the simulations show strong defect-recombination effects that lead to a saturation of the total defect number after a few hundred impacts, while sputtering leads to an imbalance of the vacancy and interstitial number. On the experimental side, surface morphology changes were investigated over a broad range of fluences, energies and temperatures for both virgin and pre-damaged W-targets. At the lowest accumulated fluences, small surface-grain features and near-surface He bubbles are observed. At the largest fluences, individual grain characteristics disappear in focused ion beam/scanning electron microscopy (FIB/SEM) scans, and the entire surface is covered by a multitude of near-surface bubbles with a broad range of sizes, and disordered whisker growth, while in top-down SEM imaging the surface is virtually indistinguishable from the nano-fuzz produced on linear plasma devices. These features are evident at progressively lower fluences as the He-ion energy is increased.
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