Effects of condensible impurities on the erosion behavior of the plasma-facing materials

Effects of condensible plasma impurities on the material erosion behaviors have been investigated by improving the previous zero-dimensional model. The new model can describe more precisely the transition from the enhanced erosion due to impurities to reduced erosion with the formation of the impurity film. Model predictions have been proven by the experimental observations in NAGDIS-I. A water-cooled molybdenum target plate was bombarded with argon plasmas into which methane was introduced as carbon impurity. As the flow rate of the methane gas was increased, MoI emission line intensity, corresponding to sputtered particle flux, has been observed to decrease to a great deal.