Modelling of hydrogen transport through plasma facing materials by use of cellular automaton

In this study, the kinetics of release of hydrogen from both surface and bulk is modelled in cellular automaton (CA). The material is modelled in two-dimensions by considering its cross section. The model consist of three parts, i.e. the desorption model expressed in one-dimensional lattice, bulk diffusion and the model which express the hydrogen transport between the bulk and the surface to connect these two models. In this manner, the interaction of gas (vacuum)-surface and surface-bulk are clearly distinguished. The conventional approach, however, assumes the equilibrium condition between the surface and the bulk to make the expression as direct relationship between the gas (vacuum) and the bulk due to the restriction of functional continuity of a differential equation. The model is utilised to simulate thermal desorption since it has a transient nature in both time and the temperature. The inclusion of the bulk into the model produced two peaks, where the first peak is responsible for the desorption of the surface adsorbed adatoms and the second peak associated with the hydrogen from the bulk and the transition of rate limiting process. Moreover, the model and the result are discussed with aid of some experimental results.