高精度真空材料放气测试研究

High-Precision Measurement of Outgassing Rates of Materials for Use in Extremely High Vacuum

材料放气率是评价真空材料性能的重要参数。高精度真空材料放气测试系统集成了定容升压法、小孔流导法和双通道转换法三种材料放气率测试方法。其独特的系统设计与加工并配备先进的泵阀计组件,使系统获得无污染清洁的超高真空,极限真空度最低达6.8×10^(-9)Pa。低的本底真空进一步降低了系统的放气率测量下限,三种方法的测量下限依次可达:6.20×10^(-12),2.90×10^(-12)和2.78×10^(-12)Pa·m^3/(s·cm^2)。针对三种方法,对应选取聚四氟乙烯(PTFE)、304和316 L不锈钢作为样品,测试了不同时间的放气率。测试结果表明:三类样品10 h内的总放气率分别在10^(-8),10^(-11)和10-12Pa·m^3/(s·cm^2)数量级,对应的最大测量不确定度分别为9.4%,12.5%和13.8%。结合四极质谱计,进一步获得样品的放气组分和PTFE各组分的放气分率,总放气率和放气分率均随抽气时间的增加而下降。

A novel test-platform,with a ultimate pressure of 6. 8 × 10^-9 Pa,was developed to precisely measure the outgassing rate of the materials for use in extremely high vacuum（ XHV） by integration of the method of pressure-rise,throughput method and method of switching between two pumping paths（ SPP）. Evaluated in the three methods,the lower detectable limits of the outgassing rates were 6. 20 × 10^-12,2. 90 × 10^-12and 2. 78 × 10^-12Pa·m^3/（ s·cm^2）,respectively. The outgassing rates of Teflon,304 and 316 L stainless steel samples,measured in three methods with the test-platform for 10 h,were in the orders of magnitude of 10^-8,10^-11,10^-12Pa·m^3/（ s·cm^2）with discrepancies of 9. 4%,12. 5% and 13. 8%,respectively. In addition,the time-evolution of Teflon outgassing rate was characterized with quadruple mass-spectrometers. The results show that the total and partial outgassing rates of H_2O,N_2（ CO） and O_2 decreased with a increase of pump-down time.