Erosion of high-Z metals with typical impurity ions

This paper reviews the erosion properties of high-Z plasma facing materials due to the bombardment with typical impurity ions. The different impurity species present in today's fusion experiments are compared in terms of their importance for erosion of high-Z metals, showing that C is the main source of erosion. As example results are presented here from controlled ion beam experiments on the temperature dependent erosion and deposition processes occurring during bombardment of W by keV C-ions. It is shown that radiation enhanced sublimation (RES) and diffusion are responsible for the observed temperature dependence. A new code was developed to simulate the influence of thermally activated processes on the complex temperature dependence of protective C layer growth on W during simultaneous bombardment by keV C and eV hydrogen isotopes. To model RES, diffusion and chemical erosion of C the Monte Carlo program TRIDYN was coupled with a newly developed diffusion code DIFFUSEDC and a chemical erosion module YCEHM. This combination was validated by comparing calculated W erosion yields in D plasma with C as main impurity to spectroscopically measured values from ASDEX Upgrade as well as ion beam experiments using CH3+