Some measurements of outgassing properties and far-infrared reflectivities of two optical blacks

Degassing rate and infrared reflectivity measurements upon proprietary optical blacks are reported. After bake-out to 250 °C, degassing rates range from 3 × 10 −7 Torr litre s −1 cm −2 at 230 °C to 1 × 10 −10 Torr litre s −1 cm −2 at 25 °C. The hemispherical diffuse and angular specular reflectivities have been measured at discrete wavelengths near 28 μm, 118 μm and 337 μm. For wavelengths less than 30 μm the blacks are shown to be essentially diffuse reflectors, with reflectivities of the order of 5%. At longer wavelengths specular reflection dominates, reaching values of up to 50% at normal incidence for 337 μm radiation. Substrate reflection is believed to be significant in this long-wavelength region.