C and D reemission from mixed W–C–D layers during single-species and simultaneous irradiations of W with C+ and D+

We present new experimental results on the reemission of C and D from tungsten during single-species and simultaneous irradiations with 6 keV C+ and 1 keV D+ ion beams. The relatively low C fraction in the combined total beam flux (∼4.5% C+/[C+ + D+]) was selected to prevent the formation of a carbon over-layer during C+ irradiation. The results show that the temperature dependence of D reemission from a mixed W–C–D surface is similar to that from pure W. In the case of a mixed W–C surface, the reemission of C was much lower than observed for pure carbon. Post-irradiation XPS analysis of the chemical bonding states of a W specimen irradiated at 973 K with 6 keV C+ shows that carbon in the mixed W–C surface is primarily in the form of WC.