Dynamic behavior of tungsten surfaces due to simultaneous impact of hydrogen and carbon ion beam

By using a simulation code for ion-solid interactions, EDDY, the dynamical behavior of W surfaces irradiated simultaneously with H+ and C+ impurity has been studied. This code models the fluence evolution of composition changes between C and W at the irradiated surface, which results from sputtering erosion and impurity deposition. The result has been described in terms of C impurity concentration in the irradiation. It has been compared with experimental data obtained by an ion beam irradiation device. In particular, the C impurity concentration has an important role in erosion/deposition at the W surface. As the C impurity concentration increases, the erosion is enhanced. As the C impurity concentration exceeds 3.00%, there is a transition from erosion to deposition which is due to the formation of a C film on the W surface. Regarding the result that the erosion changes to deposition, the simulation qualitatively reproduces the experimental results measured by X-ray photoemission spectroscopy (XPS). There is a different tendency in the fluence dependence for the different C impurity concentrations. For C:0.11%, the erosion rate increases with increasing fluence. This results from a growth of a local peak at around a depth of 20 nm in the depth profile of the deposited C. The growth is in good agreement with the experimental result, which shows that there is a strong contribution from recoil implantation of the deposited C due to a synergetic effect of the H and C impurity. For C:0.84%, there are almost the same tendencies as for C:0.11% in the erosion rate and in the depth profile. However, the growth of the local peak at around a depth of 10 nm is in disagreement with the measured one, which occurs near the surface. The disagreement appears to be attributable to the contribution of the surface segregation. (author)