Thin film heater for removable volatile protecting coatings

Area of Science:

• Materials Science
• Optical Engineering
• Astronomy Instrumentation

Background:

• Aluminum mirrors exhibit high reflectivity in the far ultraviolet (UV) spectrum, essential for space-based telescopes.
• Exposure to atmospheric conditions causes rapid degradation of aluminum mirror reflectivity, limiting their operational lifespan and performance.
• Protective over-coatings are necessary to preserve mirror reflectivity, but must be removable without compromising optical properties.

Purpose of the Study:

• To demonstrate the feasibility of using a Nickel-Chromium (NiCr) thin film heater for re-evaporating a volatile protective coating on aluminum mirrors.
• To confirm that the re-evaporation process does not negatively impact the reflective properties of the underlying aluminum mirror surface.
• To validate a protective coating removal method for applications in UV space astronomy.

Main Methods:

• Application of a removable volatile zinc (Zn) coating onto freshly prepared aluminum (Al) mirror surfaces.
• Utilizing a NiCr thin film heater to controllably heat and re-evaporate the Zn protective coating.
• Post-re-evaporation analysis to assess the reflectivity of the Al mirror surfaces.

Main Results:

• Successful re-evaporation of the volatile Zn protective coating was achieved using the NiCr thin film heater.
• The reflectivity of the aluminum mirror surfaces remained unaffected after the Zn coating removal process.
• The method proved effective in preserving the optical integrity of the mirrors.

Conclusions:

• Re-evaporation of volatile protective coatings on aluminum mirrors using NiCr thin film heaters is a viable technique.
• This method is suitable for preserving mirror reflectivity in demanding environments like UV space astronomy.
• The developed technique offers a practical solution for maintaining optical performance of sensitive mirror surfaces.