a The experimental setup, showing how the two sample regions were created. b Distribution of primary radiation damage (blue dots) and proton deposition (red dots) along the irradiation direction for the Ni-20Cr corrosion experiments, simulated by SRIM32. c Schematic of the irradiated (in orange) and unirradiated (in green) zones. d–l Optical and representative SEM images of the beam-facing side of the Ni-20Cr foils after 4 h at 650 °C under various beam current densities. d–f, g–i, and j–l Correspond to beam current densities of 2.5, 2.0, and 1.5 μA cm−2, respectively. Scale bar: 200 μm.