Hydrogen implantation effect in copper alloys selected for ITER investigated by positron annihilation spectroscopy

Abstract

Defects in the form of vacancies (loops, voids, etc) created by hydrogen implantation into selected Cu alloys foreseen for the International Thermonuclear Experimental Reactor (ITER) first wall cladding were studied using positron annihilation spectroscopy. The pulsed low-energy positron system, which enables depth profiling of the positron lifetime spectra in the near-surface region (20–460 nm) of hydrogen-implanted copper alloys, was applied, and its results were compared with TRIM calculations and transmission electron microscopy studies. The selected specimens were implanted in the Ion Beam Laboratory of FEI STU Bratislava. The energy of implantation was EH = 2 × 95 keV for the molecular ion beam. The temperature during this process was lower than 90°C. Two implantation doses were chosen for both the alloys: 1.3 × 1019 ions cm−2 (1.1 C cm−2) and 5 × 1018 ions cm−2 (0.4 C cm−2). Although the influences of neutrons with energy 14 MeV and protons with energy 95 keV are not the same (differences in energy and existence of proton charge), experimental simulation of radiation damage of ITER construction materials was successfully performed. The results are discussed in terms of microstructural changes of the studied materials upon irradiation. The CuAl25 alloy seems to be more resistant to proton bombardment than CuCrZr.