Effects of a simulated high-energy space environment on a LaF₃/MgF₂ multilayer

Due to their low absorption, the LaF 3 /MgF 2 material pair is widely used in the far-ultraviolet space payload. In the space environment, there are plenty of energetic particles (electrons, protons, γ rays, and atomic oxygen) and strong ultraviolet lines. These energetic particles penetrate into the films, and may change the materials’ physical and chemical structures. Hence, these energetic particles and ultraviolet lines may degrade the performance of LaF 3 /MgF 2 . We examined the effect of a simulated high-energy space environment on a LaF 3 /MgF 2 multilayer. Dendritic patterns were observed in LaF 3 /MgF 2 multilayer irradiated by the 30 keV electrons. The generation mechanism was proposed. This pattern was gradient wrinkle delamination due to the electric discharge, and it was non-uniform, asymmetric. This problem can be avoided by decreasing the substrate heating temperature and lay number (total thickness), and choosing the fluoride material substrate. The LaF 3 /MgF 2 multilayer demonstrated no changes after the irradiation of the protons, γ rays, atomic oxygen, and ultraviolet lines.