He-cooled divertor: Study on low-temperature design using Ta alloy as thimble material

A modular He-cooled divertor concept for DEMO has been developed at KIT under the EU PPCS with the goal of reaching 10 MW/m². The reference design is based on a modular tungsten-based cooling finger, which consists of a tungsten tile as thermal shield brazed to a thimble heat sink made of W-1 wt% La₂O₃ (WL10). The lower temperature of the divertor operating temperature window is dictated by the ductile-brittle transition temperature and the upper temperature by the recrystallization temperature of WL10 material, assumed at 600 °C and 1300 °C, respectively, under irradiation. In this study, another design option based on the use of tantalum alloy T-111 as an alternative thimble material is investigated, which offers a potential for the exploitation of material ductility, and thus the possibility of a lowering the DBTT temperature limit.