New Insight into the Quantifying Vacancy Distribution in Self-Ion-Irradiated Tungsten: A Combined Experimental and...

We present a new approach using positron annihilation spectroscopy to estimate the concentrations of vacancy-type defects induced by self-ion irradiation in tungsten at various temperatures. We extracted complete vacancy distributions from experimental data using quadratic programming and a simulated annealing algorithm parametrized with a positron trapping model, including annihilation characteristics calculated by a two-component density functional theory for various vacancy clusters. The method was validated against simulation results and transmission electron microscopy (TEM) observations. After irradiation at high temperatures, small clusters undetectable by TEM were unveiled, with concentrations significantly exceeding TEM-visible defects (10²⁴ m^-3). Taking into account positron trapping in the oxygen-vacancy complex accurately replicates the high-temperature irradiation experimental data.