Accelerator Mass Spectrometry from 1979 till 2009
Accelerator Mass Spectrometry (AMS) has made a revolutionary contribution to the measurement of cosmogenic radionuclides. Cosmogenic radio nuclides are produced in nuclear reactions by fast particles from the cosmic rays. On the Earth they are produced in the atmosphere ( 10Be, 14C) and in situ on the surface in rocks (10Be, 14C, 26Al) and ice (14C). As the production is modulated by the activity of the Sun and the geomagnetic field the concentrations of the radio nuclides form an archive with information on these parameters, which may also have induced climatical variations.
The cosmogenic radio nuclides have extremely small concentrations. Compared to its stable isotope they have isotope ratio's in the range of 10-12 to 10-15. In AMS these small concentrations are measured by counting individual atoms, which is realized by a combination of ion beam and detection techniques developed in nuclear physics. In radiocarbon dating of small samples, 1 mg of carbon (or even less) AMS has contributed to a broad range of disciplines. The importance of AMS has been also recognized in biomedical applications with tracer studies with very low doses of 14C and 41Ca, which can be performed in vivo and in vitro.
The AMS-facility in the Van de Graaff laboratory of Utrecht University is based on the 6 MV tandem Van de Graaff accelerator, which has been used originally for precision research of nuclear spectroscopy. The accelerator has been adapted for AMS with stable beam transmission and minimal beam loss. Precision measurements are made with fast switching between isotope beams in an automated scheme. Participation in intercomparison studies confirms the quoted precision. Chemical preparation techniques have been setup to isolate the suited chemical fractions in applications.
Analyses are performed in
a broad range of research disciplines. Most of these concern radiocarbon
dating for applications in earth sciences and cultural sciences, an to a
lesser extent with other radio nuclides. Analyses are performed as part of
projects or are as a service at the corresponding