Development of an absorbing first wall interface for small fusion devices

Tantalum (Ta) is known for its hydrogen storage property, high melting point and favorable resistance to sputtering. These properties bring forth interest in Ta as a plasma-facing material (PFM) for small-scale fusion devices which need to operate at low neutral pressures. Tantalum is foreseen as a PFM for the Wisconsin HTS Axisymmetric Mirror (WHAM). WHAM is a compact, high-field mirror design. Explorations of Ta are underway to investigate its potential as a neutral getter to improve plasma performance. This study aims to test whether Ta deposited by cold spraying can withstand high heat loads, particle erosion and effectively retain hydrogen isotopes. In these experiments, stainless steel rods were cold sprayed with Ta powder with five spraying conditions where temperature and proportion of carrying gasses (N₂/He) were varied. The samples are being prepared for testing via surface and bulk diagnostics before and after deuterium plasma exposure in the PSI-2 device. This will allow for examination of the effects of the particle and heat fluxes on the material’s retention capabilities and physical properties. Future development of the cold spraying technique may allow for its use in fusion devices with in-situ deposition of various materials on the surfaces of plasma-facing components.