Numerical method of in-situ measurement of dewar heat leakage

A numerical method of in-situ measurement of the heat leakage of dewar including radiative heat leakage, conductive heat leakage and total heat leakage was proposed. Using the functional relation between the temperature change of the cold head of the dewar and the heat leakage, the mathematical expression of the heat leakage by numerically fitting the temperature change curve of the cold head was reversely derived. This method makes it possible to get the radiative heat leakage and conductive heat leakage simultaneously under the condition of unchanging the coupling of dewar with refrigerator. It gives the solutions not only for finding the cause of thermal abnormity but also getting the value of both radiative and conductive leakage at each temperature. Experiments show that this method is simple and efficient with reliable result. It provides an effective tool for thermal design and failure analysis of the dewar.