Outgassing Characteristic Study of Internal Material in Dewar

Vacuum failure of a long-lifetime Dewar is mainly due to internal outgassing.The outgassing properties of the internal material in a Dewar are tested by using a Quadrupled Mass Spectrometer(QMS). The analysis result shows that the gas consists mainly of H_2O,CH_4,H_2 and so on.The model of outgassing properties is established according to the nonmetal outgassing theory.The result is valuable to material selection,optimization of outgassing techniques and Dewar exhausting.