In search for lost atoms: benchmarking 10Be & 26Al measurements at ANSTO

To utilise cosmogenic nuclide methodology in applications where ¹⁰Be and/or ²⁶Al concentrations are low, such as late Holocene glacial deposits or long burial ages, one is limited by the analytical sensitivity. Similar situation may arise if available sample size is small. Consequently, to expand the applications of cosmogenic isotopes into new areas there is a need to improve the efficiency of the method.

To improve the current analytical sensitivity of the cosmogenic isotope technique we have essentially two options: to increase the amount of sample material or reduce the losses in accelerator mass spectrometry (AMS) measurement. Given larger sample sizes are not always possible or practically feasible our only option left is to look at improving the actual measurement efficiency.

Losses during an AMS measurement occur in the ion source, in the transport of ions through the spectrometer and in the ion detection stage. In this presentation each of these key stages of an AMS measurement will be discussed and losses quantified with particular view to discuss possible avenues for improvement. Finally, given any potential improvement in efficiency of the measurement needs to be achieved without compromising other performance characteristics current performance from ANSTO will be presented and benchmarked.