The first six to eight years of DREAMS (DREsden Accelerator Mass Spectrometry): On our way to cloud nine?

Since 2009, the DREAMS (DREsden Accelerator Mass Spectrometry) facility offers users to do their own sample preparation for producing AMS-targets. Two years after the 6 MV-based tandem accelerator measured the first unknown samples for long-lived radionuclides [1]. AMS reduces background and interfering signals resulting from molecular ions and isobars enormously. Thus, AMS provides much lower detection limits compared to conventional MS or decay counting. DREAMS offers excellent measurement capabilities also for external users [2].
AMS allows thousands of exciting applications, especially within environmental and geosciences. In nature, the so-called cosmogenic nuclides (CNs) are products of nuclear reactions induced by primary and secondary cosmic rays. Hence, they can be found in extraterrestrial material such as meteorites - originating from the asteroid belt, the Moon or Mars - and lunar samples in higher concentrations (e.g. ~10^{10 10}Be atoms/g or < 0.5 mBq/g). A combination of several CNs is used to reconstruct the exposure history of this unique material while in space (irradiation age) and on Earth (terrestrial age).
Though, in terrestrial material the concentrations are typically only on the order of 10⁴-10⁹ atoms/g (i.e. μBq/g - nBq/g) for ¹⁰Be produced in the Earth’s atmosphere, then transported to the surface and further absorbed and incorporated at and in e.g. sediments or ice. Some of the lowest ¹⁰Be concentrations (~10³ atoms/g), produced in-situ by neutron- and muon-induced nuclear reactions from e.g. oxygen and silicon in quartz, can be found in samples taken from the Earth’s surface. The concentrations of atmospheric or in-situ produced CNs record information that is used to reconstruct sudden geomorphological events such as volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earthquakes [e.g. 3] and glacier movements. These movements and data from ice cores give also hints for the reconstruction of historic climate changes and provide information for the validation of climate model predicting future changes. Slower processes such as sedimentation, river incision and erosion rates can also be investigated and indirect dating of bones as old as several Ma’s is possible. Finally, remnants of supernova-produced nuclides can also be found in deep-sea archives (sediment, crust, nodule) [e.g. 4].
Anthropogenic production e.g. by release from nuclear reprocessing, accidents and weapon tests led to increased radionuclide levels in surface water, ice and soil (³⁶Cl, ¹²⁹I,…). Hence, some nuclides can be used as tracers to follow pathways in oceanography, to date and identify sources of groundwater, to perform retrospective dosimetry and to study aspects in radioecology and pharmacology. Obviously, also nuclear installation materials are radioactive (³⁶Cl, ⁴¹Ca,…).

References: [1] G. Rugel et al., Nucl. Instr. Meth. Phys. Res. B. 2016, 370,94. [2] www.hzdr.de/ibc for beam time application. [3] W. Schwanghart et al., Science 2016, 351,147. [4] A. Wallner et al., Nature 2016, 532, 69.