Stable high-reflection Be/Mg multilayer mirrors for solar astronomy at 30.4  nm

Area of Science:

• Space Physics and Astronomy
• Materials Science

Background:

• The Sun's corona is studied using specific spectral channels, including the Helium II (He-II) emission line at 30.4 nm.
• Developing advanced optical coatings is crucial for enhancing the sensitivity and accuracy of solar observation instruments.

Purpose of the Study:

• To investigate novel multilayer coatings for improved performance in solar corona spectral analysis.
• To evaluate the reflectivity, spectral width, and temporal stability of new beryllium/magnesium coatings.

Main Methods:

• Fabrication of multilayer coatings comprising beryllium (Be) and magnesium (Mg) layers.
• Incorporation of these novel coatings beneath a protective aluminum and Be bilayer.
• Characterization of the coatings' optical properties, including reflection coefficients and spectral width (Δλ).
• Assessment of the temporal stability of the coatings under relevant conditions.

Main Results:

• Achieved exceptionally high reflection coefficients of up to 56% for the He-II line.
• Obtained a narrow spectral width of Δλ=1.6 nm (λ/Δλ≈20), ensuring spectral purity.
• Demonstrated high temporal stability, crucial for long-term solar monitoring.

Conclusions:

• The novel Be/Mg multilayer coatings represent a significant advancement for solar corona research.
• These coatings offer superior performance characteristics compared to existing technologies for the 30.4 nm He-II line.
• The improved reflectivity and stability will enhance the capabilities of instruments used in solar physics.