The effect of W surface fuzz induced by He plasma on deuterium permeation

The permeation and retention of hydrogen isotopes in nuclear materials are critical to issues like hydrogen embrittlement, tritium self-sufficiency, and radioactive safety in fusion reactors. Tungsten, the primary candidate for plasma-facing materials (PFMs), undergoes high-flux helium plasma irradiation in fusion devices that may alter hydrogen isotope behaviors. However, few works focused on the effects of helium plasma-induced surface modification on hydrogen permeation. This study investigates the effect of helium-induced surface fuzz structure on deuterium permeation through tungsten. The results indicate that the surface fuzz structure can significantly enhance deuterium permeation through tungsten, with the degree of enhancement positively correlated to both the thickness of the fuzz structure and the permeation temperature. In addition, as the temperature decreases, the contribution of the tungsten oxide layer covering the nanotendrils that hinder deuterium diffusion gradually becomes stronger, resulting in the weakening of the overall permeation enhancement. The influences of the fuzz characteristics on deuterium transport properties are discussed. This work implies that the helium plasma-induced surface modification can significantly change the deuterium transport behaviors in tungsten.