Surface-morphology changes and damage in hot tungsten by impact of 80 eV - 12 keV He-ions and keV-energy self-atoms
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Meyer, Fred W↗
Engineering topics
Dadras, Mostafa Jonny
Publications and source records attributed to Dadras, Mostafa Jonny.
He-Ion and Self-Atom Induced Damage and Surface-Morphology Changes of a Hot W Target
We 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 (MIRF), 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 hundreds 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 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 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.
Meyer, Fred W↗
Improved Hydrocarbon Potentials for Sputtering Studies
We refit the REBO hydrocarbon potentials by reparameterizing the bond lengths and energies of hydrocarbons with recent data, using systematic addition of the parameters of all hydrocarbons CxDy with x equal or less than four. In addition we also refit the short-distance potentials to reproduce a repulsive ZBL term. To test the improved potential, we performed large scale molecular dynamics calculations of amorphous deuterated carbon bombarded by deuterium, and compare our results with data obtained using the REBO potential as well as with recent experiments.
Kent, P.↗