Modeling of materials mixing behavior among beryllium, carbon and tungsten as plasma-facing materials under deuterium and tritium plasma bombardment

If in-vessel components in a magnetic fusion device employ two or more different plasma-facing materials, materials mixing can occur due to the impurity transport along with erosion and redeposition. Materials mixing alters surface characteristics, which in turn affects plasma interactions behavior with in-vessel components. Currently, the use of beryllium, carbon and tungsten as plasma-facing materials is under consideration for in-vessel components for the International Thermonuclear Experimental Reactor (ITER). However, there is no standard model applicable to analyze the materials mixing behavior. In this study a zero-dimensional materials balance model has been applied to analyze the behavior of deposition and removal of plasma impurities over in-vessel components under deuterium and tritium (DT) particles bombardment for the purpose of evaluating the possibility of materials mixing via impurity deposition. It is found that materials mixing between beryllium and carbon is likely whereas tungsten tends to remain without beryllium and carbon impurity deposition. In contrast, the model predicts that beryllium and carbon plasma-facing components will be highly susceptible to the deposition of tungsten impurities.