For future studies of oceanic circulation it is necessary to develop the tritium measurement via 3He ingrowth into a routine procedure with a high capacity for efficient use. This paper attempts to demonstrate that this can be achieved using a commercial helium isotope mass spectrometer and special procedures for sample preparation, storage for 3He ingrowth, and 3He transfer from the ingrowth containers into the mass spectrometer. This method allows for measurement with a much higher precision and lower detection limit than is possible with counting techniques. Additionally, the parameters and blanks in routine operation of the system are discussed.
Inhalt
1 Introduction.- 2 General Procedure.- 3 System Configuration.- 3.1 Gas Extraction Units.- 3.2 Inlet System.- 3.3 Mass Spectrometer.- 3.4 Computer Control.- 4 System and Handling Details.- 4.1 Gas Extraction Systems.- 4.1.1 Small Volume Samples.- 4.1.2 Large Volume Samples.- 4.2 Inlet System.- 4.2.1 Sample Inlet.- 4.2.2 Air Standards.- 4.2.3 Sample Purification.- 4.2.4 Helium/Neon Separation.- 4.3. Mass Spectrometer.- 4.4 Measurement of the 3He/4He Ratio.- 4.4.1 Procedure.- 4.4.2 Precision and Reproducibility.- 4.4.3 Non-linearity Effects.- 4.5 Tritium Measurement.- 4.5.1 Procedure.- 4.5.2 Standardization.- 4.5.3 3He Detection Limit.- 4.5.4 Data Evaluation.- 5 Blanks.- 5.1 Helium Measurement.- 5.1.1 Sampling and Sample Storage.- 5.1.2 Sample Extraction.- 5.2 Tritium Measurement.- 5.2.1 Tritium Blanks.- 5.2.2 3He Blanks.- 6 'Ultra Low Level' Tritium Measurements.- 7 Intercalibration.- Acknowledgements.- References.