Accelerator mass spectrometry (AMS) is a versatile technique for the determination of ratios of long-lived radioisotopes (half-lives in the order of kyr -100 Myr) to stable isotopes of the same element. It covers a broad range of applications from environmental sciences over astrophysics to nuclear safeguards. As such, the investigated samples have isotopic ratios spanning many orders of magnitude. In the first step of an AMS measurement these samples are sputtered in an ion source. This can lead to direct sample to sample contamination and contamination of the ion source on longer time scales (long-term memory effect).
Understanding these processes is of particular importance for AMS of volatile elements like chlorine or iodine where remobilization and ionization of material in the ion source is more likely to occur. Here, ion source memory can represent a limitation for the precise and accurate determination of low radioisotope concentrations in e.g. environmental samples. In an interlaboratory collaboration with the ETH Zuerich and the University of Vienna our group is investigating these effects.
In this project an interested student can be involved in preparing and performing ion source contamination measurements at the 14-million-volt accelerator at the ANU, and in the data evaluation and modelling of the experimental results performed at participating facilities.