Deuterium trapping in rolled polycrystalline tungsten exposed to low energy plasma

Abstract

Deuterium retention after low energy plasma exposure was investigated using the polycrystalline tungsten samples of which grain elongation directions are parallel and perpendicular with respect to the surface. The deuterium retention calculated from TDS spectra is 2 - 10 times larger in the sample with perpendicular grain elongation direction than in the parallel one for the irradiation temperatures of 450 - 750 K. Removing of the grain elongation anisotropy by the recrystallization resulted in disappearance of the difference in the deuterium retention of the both kinds of samples. No bubbles and no blisters have been observed in the near surface layer of the samples. Plasma irradiation should produce high energy defects that are responsible for the deuterium retention. The difference in the retention of the both kinds of samples seems to be attributed to the different effective diffusion coefficients depending on the grain elongation direction. ©2012 The Japan Society of Plasma Science and Nuclear Fusion Research.