Erosion of tungsten and its brazed joints with bronze irradiated by pulsed deuterium plasma flows

This work presents results on erosion of mono- and polycrystalline tungsten and its brazed joints with bronze substrates under irradiation by high-temperature pulsed (τp ∼ 20 μs) deuterium plasma flows, with a power density q = 19–66 GW/m2 and pulses numbering from 2 to 10, simulating the expected plasma disruptions and ELMs in fusion reactors. The surface erosion and heat resistance of tungsten and brazed joints were investigated by scanning electron microscopy, and erosion coefficients were determined by target mass loss. It is found that for both types of tungsten the surface starts to significantly crack even under relatively weak irradiation regimes (q = 19 GW/m2, N = 2), at which point surface melting is not observed. Local melting becomes visible with an increase of q up to 25 GW/m2. In addition, there is formation of blisters with a typical size of 1–2 μm on the surface of monocrystalline samples and craters up to 2 μm in diameter on polycrystalline samples. In addition, craters ∼10–30 μm in diameter are formed on defects similar to those observed under unipolar arcs. At that point, the erosion coefficients change to within ranges of 0.2–0.7 × 10−5 kg/J m2. It is found that at q = 50 GW/m2, the brazed joints of monocrystalline tungsten with bronze of Cu-0.6% Cr-0.08% Zr have the highest heat resistance.