Prediction of temperature range for the onset of fuzz formation in helium-plasma-implanted tungsten

Abstract

We describe model predictions of the temperature dependence for the formation of fuzz, a nanofiber-like surface feature, on helium-plasma-irradiated tungsten surfaces under conditions similar to those at the divertor of fusion reactors. Temperature influences the onset of fuzz formation through the strongly temperature-dependent pressure of subsurface helium bubbles formed by plasma implantation and surface diffusivity of tungsten, in addition to the thermal softening of the elastic moduli of tungsten. We explore the effects of helium concentration in the plasma-implanted tungsten and helium bubble size, report surface response diagrams predicted over a broad temperature range, and interpret the trends exhibited in such diagrams.