Blistering of polycrystalline and monocrystalline niobium

Abstract

Radiation blistering of niobium surfaces has been investigated for normally incident He⁺ and D⁺ projectiles. For the He⁺, the bombarding energies were 0.5 and 1.5 MeV, the targets were both monocrystalline and polycrystalline niobium at room temperature and at 900°C, and the total dose was from 0.01 to 1.0 C/cm². For cold-worked samples at room temperature, 0.5-MeV He⁺ ions produced large blisters (up to 500 μm in diameter), many of which were ruptured; 1.5-MeV He⁺ ion implantation produced one big blister covering most of the irradiated area. For the D⁺ ion implantation, the bombarding energies were 0.250 and 0.5 MeV and the targets were all polycrystalline. Implanting 0.250-MeV D⁺ ions in annealed polycrystalline Nb at 700°C produced small blisters for doses ranging from 1.6 to 3.0 C/cm². Preliminary results on the skin thicknesses of ruptured blisters indicate a close relationship between the thickness and both the projected range of the ions and the peak in the defect distributions.