Al/Zr-based multilayer mirrors with record-breaking reflectivity

The paper reports on a new Zr/Be/Si/Al multilayer structure that provides record reflectances of up to 67% and a spectral resolution of Δλ = 0.63 nm (λ / Δλ ≈ 27) in the spectral range of 17-20 nm. It is shown that the structure has a high temporal stability of extreme ultraviolet (EUV) optical characteristics. This fact makes the structure promising for future missions to study the solar corona.