Interaction of a Hydrogen plasma with Sn-Li eutectic as a potential fusion Plasma Facing Component (PFC) material*

One of the significant obstacles left if the development of a fusion power plant is the development of Plasma Facing Components (PFCs) that can withstand the large heat and particle flux incident on the first wall and divertor region. As solid PFCs struggle with microstructure growth, sputtering and melting, liquid metals have been a popular potential replacement. Liquid metal's use as a PFC has been increasing due to its ability to self-repair damage as well as pump lost fuel and waste particles to create a low recycling edge. Currently, tin, lithium and lithium eutectics are the commonly considered liquid metals for use as a fusion PFC. It is therefore important to research the Plasma Material Interaction (PMI) between a hydrogen plasma and the liquid metal PFC candidates. Previously at the Center for Plasma Material Interaction (CPMI), the interaction between a hydrogen plasma and a free molten tin surface was investigated and it was found that tin is ejected in the presence of a hydrogen plasma at a rate that increases with increasing flux of atomic hydrogen to the surface. Making tin a less appealing PFC than something like lithium that chemically getters any incident atomic hydrogen. However, lithium's reactivity makes it both difficult to handle and work with as it will readily react with impurities or corrode components it comes into contact with. One alternative is the tin-lithium eutectic which is less reactive than pure lithium and has a higher vapor pressure making it easier to handle and work with both outside and inside the fusion device. Subsequently, it is important to investigate how tin-lithium interacts with a hydrogen plasma, with this work exposing the eutectic mixture of tin-lithium to a hydrogen plasma at varying hydrogen radical fluxes to investigate the interaction between them, focusing on the if the ejection of the molten Sn-Li PFC occurs similarly to pure molten tin.