The status of the AMS facility at the Institute of Geological and Nuclear Sciences' National Isotope Centre was last published in the Proceedings of the AMS-7 conference in 1996 (Tucson, Arizona). This also included an overview of the future upgrade plans for the facility. The EN-tandem was successfully converted from the belt-charging to a Pelletron system in September 2001. This has significantly reduced the risks of major downtime and greatly improved stability of the terminal voltage. The Pelletron system has a low and predictable need for maintenance. Combined with other maintenance needs inside (eg. replacement of stripper foils), tank openings now take place once a year. A new beamline was built to reject beams that can interfere with the detection of the rare isotopes 14C, 10Be, and 26Al. The only beam-optically active elements in this beamline are a quadrupole doublet and a Wien filter. This new beamline provides a significantly better rejection of interferences and an improved transmission towards the gas-ionisation detector. We are currently implementing a modern data acquisition system that allows faster pulsed electrostatic bouncing between the isotopes for sequential injection into the tandem accelerator. This will result in a more precise measurement of the stable-isotope beams, with a substantial improvement expected for the 13C/12C ratio.
Methods for 10Be analysis in marine sediments have been improved further, particularly for sediments with low concentrations of 10Be, by minimising the amount of 9Be carrier. A near-quantitative chemistry and a single-ion exchange separation are essential in which beryllium is absorbed while most matrix elements pass through as complexes.
In the Rafter Radiocarbon Laboratory, recent developments in sample preparation procedures have focussed on providing more accurate ages of sediments and soils and on the dating of small samples, down to about 0.035 mgC. We have developed a method for the separation and concentration of pollen based on density separation. Improvements of the chemistry for the radiocarbon dating of phytoliths are reported in a separate paper during the conference. Emphasis on the dating of very small samples has been possible due to the construction of a new vacuum line for the graphitisation of samples less than 0.2 mgC.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)