Radiation damage effects in far-ultraviolet filters, thin films, and substrates

Area of Science:

• Materials Science
• Optical Engineering
• Space Science

Background:

• Thin-film filters are crucial for VUV applications, particularly in space imaging systems.
• Satellite missions expose instruments to significant radiation doses, potentially degrading optical components.
• The radiation tolerance of common thin-film filter materials in the VUV spectrum was previously unassessed.

Purpose of the Study:

• To evaluate the radiation damage effects on thin-film VUV filter materials.
• To determine the suitability of these filters for space-based imaging systems subjected to high radiation environments.
• To quantify radiation-induced changes in transmittance and reflectance.

Main Methods:

• Thin films of Al(2)O(3), BaF(2), CaF(2), HfO(2), MgF(2), and SiO(2) were fabricated on various substrates.
• Samples included single layers, uncoated substrates, and multilayer filters.
• Optical properties (transmittance, reflectance) were measured before and after irradiation with 250 krad of Cobalt-60 gamma radiation across UV spectrum.

Main Results:

• No significant radiation-induced losses in transmittance or reflectance were observed between 120-180 nm.
• Minor radiation-induced absorption (2-5%) was detected near 260 nm in some samples with MgF(2) substrates.
• Overall, the tested materials demonstrated high radiation tolerance for VUV applications.

Conclusions:

• Thin-film VUV filters made from the evaluated materials are suitable for space applications with radiation exposure up to 250 krad.
• The materials exhibit excellent stability in the far-ultraviolet range under significant radiation.
• Minimal spectral changes suggest high reliability for satellite-based optical instruments.