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AMS within CoDustMas: Nanodiamonds and SN-signatures
Wallner, A.; Vockenhuber, C.; Güttler, D.; Feige, J.; Fifield, L. K.; Korschinek, G.; Melber, K.; Merchel, S.; Ott, U.; Paul, M.; Rugel, G.; Steier, P.; Tims, S.
Via accelerator mass spectrometry (AMS) two relevant aspects to dust formation and evolution are studied in the laboratory: First, the measurement of trace element isotope ratios in presolar nanodiamonds isolated from meteorites, e.g. isotope ratios of stable Pt isotopes to extract r-process nucleosynthesis signatures. Recent experiments demonstrate the applicability of AMS for measuring Pt isotope signatures in material from the Allende meteorite [1,2]. The second aspect relates to the search for live supernova (SN)-produced radionuclides in terrestrial deep-sea archives [3-5]. In particular, we focus on longer-lived isotopes with half-lives of the order of million years. Previous time-resolved measurements of a deep-sea manganese crust identified a clear 60Fe enrichment about 2.5 Ma in the past . This anomaly is interpreted as evidence for a nearby SN. With improved time resolution we continue this search by investigating two deep-sea sediment cores from the Indian Ocean for a possible signal of the SN-candidates 26Al, 53Mn, 60Fe, and potentially 244Pu .
An overview of the technique of AMS will be given and its potential for such studies and some selected applications will be discussed. In particular, the experimental proof of r-process scenarios via the direct observation of nuclides generated in the r-process such as the significance of new data for Pt isotope ratios measured in nanodiamonds will be presented and new technical approaches will be detailed [1,2]. We will exemplify the high sensitivity of AMS via the search of r-process 244Pu complementing the recent finding of live 60Fe in a manganese crust.
References:  U. Ott et al. PASA 29 (2012) 90;  A. Wallner et al. NIMB (2012);  J. Ellis et al., AstrophysJ. 470 (1996) 1227;  G. Korschinek et al., Radiocarbon 38 (1996) 68;  M. Paul et al., J.Radioanal.Nucl.Chem. 272, (2007) 243;  K. Knie et al. PRL 93 (2004) 171103;  J. Feige et al. PASA 29 (2012) 109.
Keywords: AMS; supernova; radionuclide; presolar grains; nanodiamonds; deep-sea sediments; meteorite
International conference of the European Science Foundation EuroGENESIS CoDustMas network action, 05.-08.11.2012, Ascona, Schweiz