Investigating Tantalum as a Plasma-Facing Component for Nuclear Fusion Reactors

Nuclear fusion is a potential source for producing unlimited environment-friendly energy. Tungsten (W) is selected as the primary candidate material for plasma facing component in nuclear fusion reactors due to its high melting temperature (3695 K), low sputtering erosion yield and strong mechanical properties. However, recent investigations on W have confirmed that it undergoes severe surface morphology changes during low energy He plasma and/or ion irradiation similar to a harsh fusion environment. Additionally, our previous studies indicate that tantalum (Ta) may show better resistance to the harsh radiation environment and is therefore worthy of investigation. Hydrogen retention properties, specifically deuterium (D) retention in Ta, are not well documented and are extremely important safety issue for fusion reactors. Consequently, we exposed Ta to a fusion-like environment of low-energy D ions and performed thermal desorption spectroscopy (TDS). Then, the samples were rapidly loaded (to avoid possible surface oxidation) into another vacuum chamber where we performed the thermal desorption spectroscopy measurements. Our investigations indicate two binding energy values for D in Ta, i.e. 1.8 eV and 2.1 eV. We observe a higher binding energy and a higher retention rate for D in Ta than W. We also observed that our results are consistent with theoretical predictions based on the absorption of D in Ta. Our preliminary results indicate that Ta shows better resistance to nanostructure formation (fuzz) than W in a fusion environment. However, this is still an open question and part of ongoing investigations