Cryogenic emissivity testing apparatus for insulating materials cooled by a cryocooler

Abstract The emissivity of low-temperature materials can exhibit variations with changes in temperature. Currently, measuring low-temperature emissivity often includes the use of cryogenic liquids like liquid nitrogen and liquid helium, which presents challenges such as handling inconvenience and limited adaptability to a broad temperature range. Furthermore, materials like aluminium-coated polyester films exhibit surface emissivity levels lower by several orders of magnitude compared to materials like copper and stainless steel, presenting significant challenges in achieving high-precision measurements. In this research, a low-temperature emissivity testing apparatus based on a pulse tube cryocooler has been developed. The measurement temperature range extends from 50 K to room temperature, and with the option to change the cryocooler, measurements at even lower temperatures, such as 4 K, can be achieved. The measurement principles and essential structural elements of the newly developed testing apparatus, designed specifically for low emissivity samples, are outlined. Additionally, preliminary experimental results from measurements on a double aluminium-coated polyester film sample at different temperatures are presented.