Accelerator mass spectrometry: ultrasensitive analysis for global science

Accelerator Mass Spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides that cannot be practically analysed with decay counting or conventional mass spectrometry. AMS allows an isotopic sensitivity of one part in 1015 for 14C and other long-lived radionuclides that are used as tracers and chronometers in a variety of disciplines, from archaeology to zoology. Some examples are given in the following. The high sensitivity of AMS makes possible the measurement of the cosmogenic radionuclides 14C, 10Be and 36Cl in annual layers of ice, yielding detailed information on palaeo-environmental conditions. 10Be, 26Al and 36Cl, produced by cosmic rays in the Earth's crust, are used to study erosion rates, chronology of volcanic flaws, movement of sand dunes and exposure ages of rocks associated with glacial events. Analysis of 14C and 129I in seawater provides evidence of rates of movement and mixing of surface waters into the main body of the ocean. AMS is being proposed as a new tool for nuclear safeguards in the detection of radionuclides, such as 129I and 236U, which can be used to trace specific nuclear activities, such as fuel reprocessing and uranium enrichment. AMS has expanded enormously 14C dating in archaeology and art, thanks to the non-invasive features of the method. Finally, biomedicine is becoming a major area of AMS usage, with applications in toxicology, drug testing and pharmacokinetics. In conclusion, during the last twenty years, AMS has made many major contributions to science and further progress can be expected in the future. An overview of recent AMS achievements will be presented. (author)