Further Studies on MgF_2-Overcoated Aluminum Mirrors with Highest Reflectance in the Vacuum Ultraviolet

Abstract

MgF₂-overcoated aluminum films with high-vacuum ultraviolet reflectance have been the subject of further investigations of the preparation parameters affecting their reflectance, and of the effect of aging and exposure to conditions likely to be encountered in their applications. Techniques for monitoring the thickness of MgF₂ by reflectance measurements with ultraviolet light and by complete evaporation of weighed quantities of MgF₂ are described. It is shown that MgF₂-protected aluminum mirrors retain their high-vacuum ultraviolet reflectance during extended exposure to air, ultraviolet irradiation, and bombardment with 1-MeV electrons and 5-MeV protons, and that such mirrors can be easily cleaned if contaminated with oil.