Evolution of surface morphology and helium bubble in tungsten under 40 keV helium ions implantation followed by deuterium plasma exposure

Abstract Surface morphology and internal microstructure of tungsten (W) pre-implanted by 40 keV mass-separated helium (He) ions with different fluences at room temperature were investigated in this work. The morphology changes of the samples were analyzed almost in situ , by repetitively examined the specified irradiation area which is marked by focused ion beam technology. As the samples were implanted by He ion with a fluence of 6 × 10 20 He m −2 , no He blisters or other microstructures could be found on the surface. When the fluence reaches 6 × 10 21 He m −2 , a large number of He blisters with the size of ∼1 μ m were observed on the W specimens. For the results of the subsequent deuterium plasma exposure, instead of deuterium-induced blistering, no changes on the W surface which pre-irradiated by He ion irradiation at low fluence (6 × 10 20 He m −2 ). Surprisingly, for He ions pre-implanted W with high fluence (6 × 10 21 He m −2 ), almost all the He blisters were cracked and their lids even peeled off. It could be attributed to the lateral stress caused by subsequent D exposure. Moreover, the size of He bubbles was also increased under subsequent deuterium exposure, suggesting that He atoms can attract D atoms. No deuterium blisters were found on these samples which were pre-implanted with high and low fluences, suggesting that He ion pre implantation can effectively inhibit the surface blistering caused by deuterium exposure.