Large-Area Low-Temperature Vacuum Blackbody System of High Emissivity and Temperature Uniformity

Large-area blackbodies are essential for the accurate radiometric calibration of large-aperture infrared optical instruments. However, current blackbody systems face limitations in emissivity and temperature uniformity, particularly at low temperatures. This deficiency is principally attributed to insufficient light absorption and uncontrolled thermal convection on the radiation surface of the blackbody. Here, by regulating optical reflection characteristics and implementing a cooling compensation-based temperature control mechanism, a low-temperature blackbody with high emissivity and temperature uniformity is developed. Simulations indicate that the designed blackbody efficiently improves the emissivity from 0.985 to 0.991 and enhances the temperature uniformity by 75% compared to traditional design. A vacuum blackbody system with dimensions of $500\times 500$ mm, operating at 150–360 K, was constructed. Measurements made in the vacuum radiation-temperature calibration facility confirmed that the experimental results were in good agreement with the simulations, achieving an emissivity of 0.992 and a temperature uniformity of 0.1 K under cryo-vacuum conditions. With its radiation performance, the developed large-area blackbody source can significantly improve calibration accuracy for large-aperture infrared optical instruments, contributing to more precise measurements in applications.