• Wollack, Edward
• Rinehart, Stephan A.
• Kinzer, R. E.

Abstract

A compact cryogenic calibration target is presented that has a peak diffuse reflectance, $R0.003$, from $800-4,800\,{ cm}^{-1}$ $(12-2\,$m). Upon expanding the spectral range under consideration to $400-10,000\,{ cm}^{-1}$ $(25-1\,$m) the observed performance gracefully degrades to $R0.02$ at the band edges. In the implementation described, a high-thermal-conductivity metallic substrate is textured with a pyramidal tiling and subsequently coated with a thin lossy dielectric coating that enables high absorption and thermal uniformity across the target. The resulting target assembly is lightweight, has a low-geometric profile, and has survived repeated thermal cycling from room temperature to $\,$K. Basic design considerations, governing equations, and test data for realizing the structure described are provided. The optical properties of selected absorptive materials -- Acktar Fractal Black, Aeroglaze Z306, and Stycast 2850 FT epoxy loaded with stainless steel powder -- are characterized and presented.

Topics

• impedance spectroscopy
• stainless steel