Berlin 2014 – wissenschaftliches Programm
MS 11.7: Vortrag
Freitag, 21. März 2014, 12:15–12:30, DO24 1.205
The upgrade of VERA for natural 236U - first results on detection efficiency and background — •Peter Steier, Joannes Lachner, Alfred Priller, Stephan Winkler, and Robin Golser — Universität Wien, Fakultät für Physik, VERA Labor, Währingerstraße 17, 1090 Wien, Österreich
Interest in the long-lived radioisotope 236U (t1/2=23.4 million years) has significantly increased recently, due to the emergence of environmental and earth science applications. Of the AMS instruments suited, none could achieve the sensitivity to address the expected typical natural isotopic ratios on the order 236U:238U = 10−13. One major limitation is the relatively low total detection efficiency. Stripping with helium was shown to be advantageous at lower energies . We have implemented this capability at VERA, which improved the yield by a factor of four. The second instrumental limitation is background caused by 235U hydrides. With our recently installed additional 90∘ magnet, we can suppress this background by several orders of magnitude. Our first measurements indicate a new instrumental limit below 236U:238U = 10−14, however, improved chemical procedures are still under development to extract such pure uranium from geological samples. Measurements of anthropogenic 236U and other actinides profit from the higher sensitivity allowing for smaller samples.
 Vockenhuber, C., et al., The potential of He stripping in heavy ion AMS. Nucl. Instr. and Meth. in Phys. Res. B 294 (2013) 382-386.