Be/Si/Al multilayer mirrors as the most promising optical elements for spectroscopy and imaging in the spectral region of 17-32†nm.

The reflective and structural parameters of Be/Si/Al multilayer mirrors have been studied. The extent of stability of their X-ray optical characteristics has been demonstrated during storage in air for 4 years and during vacuum annealing at temperatures up to 100°C. A high reflectance of 62.5% was obtained, together with a spectral selectivity of λ/Δλ≈59 at a wavelength of 17.14 nm and 34%, with λ/Δλ ≈ 31 at a wavelength of 31.3 nm. It was shown that Si interlayers reduce the interlayer roughness from 0.45 to 0.20 nm.