Characterization of plasma in the HiPIMS facility for simulation of fusion-oriented W co-deposition in He/H2 and He/D2 environments

Abstract

A new facility based on a HiPIMS (high-power impulse magnetron sputtering) discharge plasma with a hot tungsten (W) target for the investigation of co-deposition of W with helium (He) and hydrogen (H₂, D₂) isotopes on W substrate was developed. To find the ion fluxes from He/H₂ and He/D₂ plasma together with W ions from W target incident on installed samples, the ion mass spectrometric study of a HiPIMS plasma was performed. The results reveal a mixed composition of ion fluxes consisting mainly of monoatomic H⁺(D⁺) and He⁺, diatomic H₂⁺(D₂⁺) and HeH⁺, and triatomic H₃⁺ ions. The content of tungsten ions does not exceed 2 % in any of the explored discharge regimes. The contributions of different species to the total flux are strongly affected by the discharge pulsing parameters, especially pulsed power density. For pulsed power densities below 200 W/cm², H₃⁺ ions in the He/H₂ or D₃⁺ in He/D₂ gas mixtures dominate in the ion flux. The opposite situation of monoatomic ion fraction (H⁺ and D⁺) prevailing over molecular ions is observed in the case of the pulse power density above the values: 400 W/cm² for prevailing of H⁺ in He/H₂ gas mixture discharge, and 900 W/cm² for prevailing of D⁺ in He/D₂ gas mixture discharge. The most suitable discharge modes are selected for future simulation of W co-deposition processes with He/H₂ and He/D₂ gas mixtures. Preliminary data on the thickness of co-deposits in various regimes have been obtained. The He retention in W irradiated at the HiPIMS facility in hydrogen plasma with ∼ 10 % He ion seeding was validated by comparison with the experimental data after irradiation of W under the same conditions in a linear plasma device.