Outgassing Characteristics of Ceramic Shell Material and Microchannel Plates of Third-Generation Low-Light-Level Image Intensifiers

Vacuum failure is a major cause of shortening the lifetime (especially storage lifetime) of low-light-level image intensifiers. In order to deeply understand the vacuum failure mechanism of image intensifiers, the gas releasing rates and compositions of ceramic shell material (95 alumina ceramic) and microchannel plates (MCPs) of third-generation low-light-level image intensifiers were measured with the static pressure-rising method and residual gas analysis by a quadrupole mass spectrometer. The experimental results show that the outgassing rate of the 95 alumina ceramic at 150 °C is about one order of magnitude higher than that at 23 °C, while the outgassing rate of the MCPs at 150 °C is only about half an order of magnitude higher than that at 23 °C, which is caused by a large number of microchannels in the MCPs. During the static accumulation of gas releasing, the outgassing rate of the 95 alumina ceramic first increases and then tend to stabilize at 23 °C, and it remains basically unchanged at 150 °C, while for the MCPs both the outgassing rates at these two temperatures increase gradually, and the outgassing rate at the higher temperature increased relatively slowly. The main gas components released from the 95 alumina ceramic and MCPs at 23 °C include H2O, H2, N2/CO and CO2. After the vacuum baking at 150 °C, the releasing ratio of H2O gas from the 95 alumina ceramic decreased greatly, and that of H2 gas increased dramatically, while the releasing ratio of H2O gas from the MCPs decreased just slightly, which indicates that the vacuum baking degassing for the MCPs is relatively difficult.