Seminar - Oliver Forstner: 'Accelerator Mass Spectrometry at VERA – Status and new developments'
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Accelerator Mass Spectrometry at VERA – Status and new developments
Dr. Oliver Forstner, VERA-Laboratory, Faculty of Physics, University of Vienna
Accelerator Mass Spectrometry (AMS) is a highly precise tool to measure minute concentrations of trace elements (mainly radioisotopes) on the ultra-trace level. Typical isotope ratios detected with AMS range from 10-12 down to 10-16. The challenge in measuring such low abundances is to eliminate all disturbing interferences by a combination of various highly selective filters. The first part of my talk will be an introduction into AMS which I will describe using the example of VERA. The Vienna Environmental Research Accelerator (VERA) is a dedicated AMS facility at the University of Vienna based on a 3 MV pelletron tandem accelerator built by NEC. Originally designed as device for radiocarbon measurements it was continuously upgraded to be a versatile machine for “all” isotopes. Radioisotopes measured at VERA range from the “standard” AMS isotopes 14C, 10Be, 26Al, 126I up to heaviest isotopes including 236U and 244Pu.
However, being a mass spectrometric technique AMS is limited by the presence of isobars. Except for some fortunate cases like 14C, 26Al or 126I even more effort has to be taken to detect the radioisotope hidden under a background of a stable isobar. In the second part of the talk I will give an introduction into the new developments at VERA with the aim of extending the range of radioisotopes available to AMS. Special focus will be given on a current research project funded by the Austrian Science Fund (FWF) in which the feasibility of using laser photodetachment of negative ions as a possible solution to the isobar problem will be studied.