• Discussion: Recovery from Tracer Contamination in AMS Sample Preparation

      Jull, A. J. T.; Donahue, Douglas J.; Toolin, L. J. (Department of Geosciences, The University of Arizona, 1990-01-01)
    • Memory Effects in an AMS System: Catastrophe and Recovery

      Vogel, J. S.; Southon, J. R.; Nelson, D. E. (Department of Geosciences, The University of Arizona, 1990-01-01)
      A sample with a 14C concentration estimated to be greater than 30,000 Modern was inadvertently graphitized and measured in an AMS system. No measurable contamination of the cesium sputter ion source was observed. Simple cleaning procedures removed the contamination from the sample preparation system, with the exception of the reaction vessel in which the sample was graphitized. Sample cross-contamination factors were estimated for all of the preparation and measurement procedures.
    • Re-Evaluation of British Museum Radiocarbon Dates Issued Between 1980 and 1984

      Bowman, S. E.; Ambers, J. C.; Leese, M. N. (Department of Geosciences, The University of Arizona, 1990-01-01)
      Dates issued by the British Museum radiocarbon laboratory between 1980 and 1984 are known to have been in error. This paper outlines the cause of the problem and the procedures adopted to revise the results affected. Where revision has been possible, on average this has given dates older by 200 to 300 radiocarbon years. The individual revised results are tabulated.
    • Superconducting Mini-Cyclotrons as AMS Instruments

      Subotic, K. M.; Milinkovic, L. S.; Zupancic, M. T.; Novkovic, D. N.; Stojanovic, M. S. (Department of Geosciences, The University of Arizona, 1990-01-01)
      We have studied the limitations of conventional mass spectrometry and have examined accelerator based methods which could help circumvent these limitations. In particular, cyclotron-based accelerator mass spectrometric (AMS) techniques are discussed with an emphasis on evaluating performances of superconducting mini-cyclotrons designed for use as AMS instruments. We discussed the design of superconducting mini-cyclotrons dedicated to radioisotope dating research.