Construction of a mass spectrometric system for isotope analysis of argon from micro-gram-size samples

在没有VG工程师的情况下安装了新的VG5400。残余气体质谱于1996年6月20日获得。在那之后，它被改进和修改。地热气体样本的氦同位素分析开始于1996年12月27日。1997年1月18日开始测量了岩石样品中稀有气体（He, Ne, Ar， Kr和Xe），其中大部分来自地幔的捕虏体。通过对低惰性气体浓度样品的分析，获得了较好的稳定性和空白水平。但是，如果与我实验室灵敏度最高的质谱仪MS-II相比，灵敏度并不令人满意。其原因可能是由于离子源中灯丝的排列不充分。它将在不久的将来得到改进。执行规格摘要1)质谱仪真空：<5x10^<-10>Torr绝对灵敏度：5x10^<-4>A/Torr（用于Ar）检测限：5x10^<-15>cm^3STP（用于Ar）同位素比分析精度：1%（用于^<40 b> Ar/^<36>Ar与5x10^<-10>cm^3STP）空白：5x10^<-12>cm^3STP（用于^<40>Ar）2)惰性气体提取和净化系统真空：<5x10^<-10> torrta加热器空白：<3x10^<-9>cm^3STP（用于^<40>Ar）激光提取空白：<10^<-11>cm^3STP（用于^<40>Ar）3)总系统可测量的稀有气体绝对体积的动态范围：10^<-7>-10^<-16>cm^3STP不同稀有气体提取方法的可用性：ta炉：mg-g样品尺寸激光提取：mg-mug （-ng）粉碎和熔化

A new VG5400 was installed without VG engineer. Residual gas mass spectrum was obtained on June 20,1996. After that, it was improved and modified. Helium isotopic analyzes of geothermal gas samples began on December 27,1996. All noble gases (He, Ne, Ar, Kr and Xe) of rock samples, mostly mantle derived xenoliths, were measured from January 18,1997. Fairly good stability and blank level have been attained through the analyzes of samples with low noble gas concentrations. However, sensitivity is not satisfactory if it is compared with that of the mass spectrometer, MS-II,with the highest sensitivity in my laboratory. The reason is probably due to an insufficient alignment of filament in the ion source. It will be improved in the near future.Summary of performed specifications1) Mass spectrometerVacuum : <5x10^<-10>TorrAbsolute sensitivity : 5x10^<-4>A/Torr (for Ar)Detection limit : 5x10^<-15>cm^3STP (for Ar)Precision of isotope ratio analysis : 1% (for ^<40>Ar/^<36>Ar with 5x10^<-10>cm^3STP^<40>Ar)Blank : 5x10^<-12>cm^3STP (for ^<40>Ar)2) Noble gas extraction and purification systemVacuum : <5x10^<-10>TorrBlank of Ta-heater : <3x10^<-9>cm^3STP (for ^<40>Ar)Blank of laser extraction : <10^<-11>cm^3STP (for ^<40>Ar)3) Total systemDynamic range of measurable absolute volume of noble gases : 10^<-7>-10^<-16>cm^3STPAvailability of different methods of noble gas extraction : Ta-furnace : mg-g sample size Laser extraction : mg-mug (-ng) Crush and melt