抄録
Non-metallic thermal insulators are investigated in order to replace “metallic super insulations” as radiation shields for cryo-cooling systems of superconducting devices, which emit and/or receive microwave radiation, such as antennas. As candidates, layered refractive wafers and multilayered thin film filters are demonstrated. Layered Germanium wafers with spacings indicate that the total infrared reflectance increases with the number of wafers, but gradually saturates because of the slight infrared absorption of Germanium. Thermal insulation experiments show that the reflection efficiency, η, assuming black body radiation is incident, correlates well with experimental thermal insulation efficiencies. On this basis, infrared reflection characteristics are obtained for a variety of filters of (Ge/BaF2)m/Si. Infrared spectra of these filters have demonstrated that single band filters have a η-maximum of-72%, and that extended filters composed of double hand filters lead to a reflection efficiency of-82%.
