Investigation of He retention in W through combined He characterization methods and cluster dynamics model

Tungsten(W) is the leading plasma-facing candidate material for the International Thermonuclear Experimental Reactor and next-generation fusion reactors. The impact of synergistic helium( He), irradiation-induced microstructural changes, and the corresponding thermal-mechanical property degradation of W are critically important but are not well understood yet. Predicting the performance of W in fusion environments requires understanding the fundamentals of He-defect interactions and the resultant He bubble nucleation and growth in W. In this study, He retention in helium-ion-implanted W was assessed using neutron depth profiling(NDP), laser ablation mass spectrometry(LAMS), and thermal desorption spectroscopy(TDS) following 10 keV room-temperature He implantation at various fluences. These three experimental techniques enabled the determination of the He depth profile and retention in He-implanted W. A cluster dynamics model based on the diffusion–reaction rate theory was applied to interpret the experimental data. The model successfully predicted the He spatial depth-dependent profile in He-implanted W, which was in good agreement with the LAMS measurements. The model also successfully captured the major features of the He desorption spectra observed in the THDS measurements. The NDP quantified total He concentration values for the samples; they were similar to those estimated by LAMS. However, the depth profiles from NDP and LAMS were not comparable due to several factors. The combination of modeling and experimentation enabled the identification of possible trapping sites for He in W and the evolution of He-defect clusters during the TDS thermal annealing process.