Dislocation-mediated trapping of deuterium in tungsten under high-flux high-temperature exposures

The effect of severe plastic deformation on the deuterium retention in tungsten exposed to high-flux low-energy plasma (flux similar to 10(24) m(-2) s(-1), energy similar to 50 eV and fluence up to 5 x 10(25) D/m(2)) was studied experimentally in a wide temperature range (460-1000 K) relevant for application in ITER. The desorption spectra in both reference and plastically-deformed samples were deconvoluted into three contributions associated with the detrapping from dislocations, deuterium-vacancy clusters and pores. As the exposure temperature increases, the positions of the release peaks in the plastically-deformed material remain in the same temperature range but the peak amplitudes are altered as compared to the reference material. The desorption peak attributed to the release from pores (i.e. cavities and bubbles) was suppressed in the plastically deformed samples for the low-temperature exposures, but became dominant for exposures above 700 K. The observed strong modulation of the deuterium storage in "shallow" and "deep" traps, as well as the reduction of the integral retention above 700 K, suggest that the dislocation network changes its role from "trapping sites" to "diffusion channels" above a certain temperature. The major experimental observations of the present work are in line with recent computational assessment based on atomistic and mean field theory calculations available in literature. (C) 2016 Elsevier B.V. All rights reserved.

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