Positron annihilation Investigations of defects in copper alloys selected for nuclear fusion technology

A positron annihilation spectroscopy (PAS) based on positron lifetime measurements, using the pulsed low energy positron system (PLEPS), is used to investigate defects create by hydrogen implantation and thermal treat of copper alloys. These alloys are designated for the use in the international thermonuclear experimental reactor (ITER). The results show that the changes in the microstructure of selected copper alloys (CuCrZr, CuAl25) depend strongly on the preparing technology of alloys as well as on the implantation dose experimentally simulating the neutron treatment. The full recovering of the structure after isochronal annealing in vacuum is observed in all implanted specimens at the temperature of 450 °C. Using the PLEPS technique, for the first time, depth profiling of the positron lifetime spectra in the near-surface region (20–500 nm) of hydrogen implanted copper alloys was performed and compared with the TRIM calculations and transmission electron microscopy (TEM) studies. Possible annihilation channels in CuCrZr and CuAl25 materials are discussed in details together with corresponding annihilation characteristics determined theoretically and using computer simulations. We discuss the results of positron lifetime measurements of the irradiated and non-irradiated CuZrCr and CuAl25 specimens. We identified the most probable types of positron trapping sites. Finally, the results are discussed in terms of microstructural changes of the studied materials upon irradiation and subsequent heat treatment.