Preliminary observations of blistering of niobium by 1–15 keV helium ions

Abstract We have bombarded at room temperature polycrystalline targets of cold-rolled Marz grade niobium with beams of helium ions of 1, 5, 10 and 15 keV at doses varying from 0.1 to 10.0 C/cm 2 . We have chosen the doses so as to obtain surfaces where the thickness removed by sputtering is respectively less than, comparable to, and greater than the implantation depths. The targets were not further treated beyond mechanical polishing. The vacuum during bombardment was 2 × 10 −8 torr. Blisters of 0.1 to 3.0 μm size have been observed. The blister covered area increases with dose up to a point, but at the higher doses the blisters, if any, are masked by a micro-relief of wide valleys, presumably sputtering-induced, and tiny pock-marks which could be small ruptured helium blisters.