Dynamic erosion and deposition on carbon and tungsten due to simultaneous bombardment with deuterium and beryllium ions in plasmas

The erosion and redeposition processes of carbon (C) and tungsten (W) exposed to high-fluence deuterium (D) plasmas containing beryllium (Be) impurity are investigated by computer simulations. At high-fluence (>1025 m−2), fluence-independent sputtering yields of C, W and the deposited Be, as well as the Be deposition rate (erosion rate) are obtained for both C and W. With increasing plasma temperature, a transition from Be deposition to W erosion occurs similarly to the case of C deposition on W [3,9], but the transition temperature is lower as a result of stronger sputtering of the deposited Be. At the Be plasma concentration of less than ∼4%, a balance between the incident and released Be is reached for both C and W at the plasma temperature of more than ∼10 eV due to the formation of Be-W and Be-C mixed layers. The dependence of the transition temperature on the Be plasma concentration and the plasma fluence is calculated.