Comparison of hydrogen retention in W and W/Ta alloys

The extreme brittleness of tungsten (W) is one of the challenges of using W as first wall material. One attempt to alleviate this problem is to use W alloys with better mechanical properties. However these alloying elements must not degrade the favorable properties of W with respect to its application at the first wall of fusion devices: low sputter yield and hydrogen inventory.In this work we investigate the hydrogen retention in the recently proposed W/Ta alloys under deuterium ion bombardment. By directly comparing pure W and W/Ta alloys with 1% and 5% Ta content we found that the W/Ta alloys retain significantly more hydrogen than pure W under identical implantation conditions.Our finding of increased hydrogen retention together with the fact that the Ta alloying did not improve the brittleness makes W/Ta alloys an unacceptable choice for the first wall of fusion devices.