TEM observation of bubbles induced by single and sequential He/H irradiation in tungsten

Bubbles induced by single-ion (He or H) and sequential-ion (H/He or He/H) irradiation in tungsten were investigated using transmission electron microscopy (TEM). Specimens were irradiated with 12 keV He+ and 6.7 keV H+ under different fluences at 600 degrees C. Bubbles were observed after single He+ irradiation. And then bubbles grew larger with the increasing of the fluence of post-irradiated H+ under sequential He/H condition. Post-implanted H+ might make bubbles grow larger. For sequential H/He conditions, the size of bubbles changed little while the number density of bubbles grew significantly compared with single He+ irradiation condition. Pre-implanted H+ might enhance bubbles nucleated. The size of bubbles was smaller while the density was larger compared with sequential He/H irradiation condition at the same fluence. Possible explanations were discussed in this paper. (C) 2017 Elsevier B.V. All rights reserved.