Carbon impurity behavior on plasma facing surface of tungsten

In order to study the behavior of carbon ions implanted together with hydrogen ions into tungsten, 1 keV H3+ (main component) with 0.1–0.8% of carbon ions were irradiated to pure sintered tungsten and depth profiles of carbon at the tungsten surface were measured. Carbon depth distributions at less than about 1000 K were much broader than the carbon ion range distributions, which could be attributed mainly to recoil implantation. Most of injected carbon atoms formed WC (not W2C) for both C ∼0.1% and ∼0.8% cases, which is different from the chemical states of carbon atoms thermally diffused into the bulk tungsten (W2C). Enhanced sputtering of carbon atoms at the tungsten surface was observed at 913 K, which might be owing to a low chemical sputtering yield for carbon.