High-Quality Graphene Membranes as a Coating for Polycrystalline Tungsten in a Nuclear Fusion Environment*

This research explores the performance of graphene as a coating for plasma facing components. A few studies have shown that graphene can act as a protective layer against sputtering due to energetic ions. We have shown that graphene can reduce and slow down changes of surface morphology caused by energetic particles, in the MITE-E facility at UW-Madison, PISCES at UC-San Diego, and C-2W at TAE Technologies. We have gained insight into the interaction of graphene with energetic ions using Raman Spectroscopy as a diagnostic for determining the damage and lifetime of the membrane. Graphene was measured to reduce secondary electron emission from tungsten. In addition, heating tests were performed of graphene on tungsten in a variable pressure deuterium environment to determine its survivability and chemical stability. Embrittlement of materials can be an issue and a residual stress analysis following the PISCES exposures found that the membrane does not have much of an effect on the internal stresses for the helium irradiation, but reduces hydrogen trapping in the bulk. We also found that graphene slows down impurity collection on the material surfaces. This research aims to expand on candidates for plasma facing components.