Influence of redeposited tungsten and EUROFER97 layers on deuterium retention in plasma-facing materials

Retention of hydrogen isotopes in plasma-facing materials is a key challenge for safety and fuel efficiency of nuclear fusion reactors. In realistic reactor environments, simultaneous processes, such as erosion, redeposition, implantation and outgassing, can alter surface compositions and may affect hydrogen isotope retention. In this study, we investigate how thin redeposited layers of tungsten and EUROFER97 influence retention and release of previously implanted deuterium. Using a combination of Elastic Recoil Detection Analysis and Rutherford Backscattering Spectrometry, we quantify deuterium retention during in-situ annealing up to 600°C. Comparisons between coated and uncoated samples show that redeposited tungsten can act as partial diffusion barrier, preventing deuterium from outgassing. In contrast, redeposited EUROFER97 layers show no such effect and appear virtually transparent to deuterium diffusion. These findings emphasize the critical role of redeposited layers on fuel retention and have implications for wall lifetime estimates and fuel inventory control in fusion devices.