Measurement of the Emissivity of Clean and Contaminated Silver Plated Copper Surfaces at Cryogenic Temperatures

An experiment has been designed, fabricated, and conducted to measure emissivity of clean and contaminated metallic surfaces at temperatures between 25 K and 35 K. Samples of silver‐plated copper with a total surface area of 0.25 m2 are secured to the coldhead of a single stage cryocooler and enclosed within an effective black thermal shield, which has an effective emissivity of 0.95 and temperatures between 275 K and 280 K. From error analysis, a sample with an emissivity of 0.020 had an experimental error between +/− 0.001 and +/− 0.002. From measurement of the radiation heat transfer, the emissivity at 30 K was 45% of the emissivity that was measured at 300 K for a set of silver‐plated copper samples. In addition, 110 μg of water vapor was sufficient to increase the emissivity of the silver‐plated copper between 50% and 200%.