Kinetics of coarsening of helium bubbles during implantation and post-implantation annealing

To understand the effects of He on irradiated metals requires modeling of helium-vacancy cluster evolution. A new method of solving the two-dimensional master equation (ME) describing He-vacancy cluster evolution has been applied to calculate helium bubble evolution in a stainless steel irradiated with alpha particles near room temperature and annealed in the temperature range of 600–900 °C. For the first time, the evolution of the helium bubble size distribution function was precisely calculated in 2-D phase space and good agreement with experimental results was obtained. The results indicate that Brownian motion of bubbles via surface vacancy diffusion provides a reasonable explanation for bubble evolution during annealing, most bubbles are found to be near the equilibrium state during the evolution at temperatures of 700 °C and higher, lack of vacancies at temperatures lower than 700 °C prevents bubble growth, and use of a non-ideal He equation of state (EOS) increases the bubble density and size relative to the case when the ideal EOS is used.