http://arxiv.org/abs/1403.6667
A compact cryogenic calibration target is presented that has a peak diffuse reflectance, $R \le 0.003$, from $800-4,800\,{\rm cm}^{-1}$ $(12-2\,\mu$m). Upon expanding the spectral range under consideration to $400-10,000\,{\rm cm}^{-1}$ $(25-1\,\mu$m) the observed performance gracefully degrades to $R \le 0.02$ 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 $\sim4\,$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.
E. Wollack, R. Kinzer and S. Rinehart
Thu, 27 Mar 14
18/62
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