The Materials Outgassing Properties And Vacuum Life Research Of MILO

High vacuum technology has been one of the most pivotal technologies for thedevelopment of high-power microwave (HPM), which is playing an important role inachieving maturity and practical applications. In the thesis, some experiments researchare carried out to measure the outgassing rate of the materials composed of microwavetube MILO and the cathode in static and dynamic state. The vacuum sealing time isestimated in static and dynamic state.Firstly, the outgassing process of the diode materials under static state is illustrated,and some outgassing models such as several molecule layers model and simpleoutgassing model are summarized and analyzed. The outgassing mechanism underelectrical pulse is analyzed.Some outgassing experiments about stainless steel, velvet, ceramic and carbonvelvet which are the main parts of the microwave tube MILO are carried out in staticpressurizing method, and these materials’ simple outgassing models are obtained usingthe former10hours’ outgassing data which reflect the trends of outgassing rates ofthese materials under high vacuum well.Electrical pulses are deposed on these cathode materials such as velvet and carbonfiber velvet to analyze the outgassing characteristics under electrical pulse operation.The result shows that velvet’s outgassing quantity keep stable nearly, and will increaseunder higher energy density condition. Through the experimental data, the conclusionthat carbon fiber velvet’s outgassing is more serious than velvet is obtained which iscaused by the developing technology.The outgassing properties comparison between static and dynamic state is madewhich shows that the outgassing quantity in static state under high temperaturepre-operation can be the same as which in dynamic state would take nearly2hours,otherwise, the time is about several seconds is estimated.Some work is carried out to improve the existing getter model in order to make itreflect the getter characteristics better. Then, some simulation is done under theconditions of different vacuum volumes, inspiration quantities, getter conductance tolearn the vacuum sealing time. The simulated result shows that the pressure in the cavitywould maintain below5×10-2Pa for400days when the activated getter’s inspirationquantity is about15Torr·L, which trend is as same as the experiment.Finally, in static state, through the comparison of the material outgassing rateformula with Arrhenius model, the vacuum sealing time would be estimated by usingthe vacuum accelerated life test method. It is estimated that the vacuum microwave tubeat room temperature would maintain below5×10-2Pa for more than one year, which isalso be reflected in the getter simulation model result. In dynamic state, it takes8 electrical pulses to exhaust whole the getter quantity about CO2.