Radiation blistering of Nb implanted sequentially with helium ions of different energies (3-500 keV)

Cold rolled, polycrystalline niobium samples were irradiated at room temperature with 4He+ ions sequentially at 14 different energies over an energy range from 3 keV--500 keV in steps of 50 keV. The dose for each energy was chosen to give an approximately uniform concentration of helium between the implant depths corresponding to 3 keV and 500 keV. In one set of experiments the irradiations were started at the Kurchatov Institute with 3 keV 4He+ ions and extended up to 80 keV in several steps. Subsequently, the same target area was irradiated with 4He+ ions at Argonne National Laboratory (ANL) starting at 100 keV and increased to 500 keV in steps of 50 keV. Another set of irradiations were started at ANL with 500 keV 4He+ ions and continued with decreasing ion energies to 100 keV. Subsequently, the same area was irradiated at the Kurchatov Institute starting at 80 keV and continued with decreasing ion energies to 3 keV. Both sets of irradiations were completed for two different total doses, 0.5 C cm-2 and 1.0 C cm-2