• Tandem Accelerator Measurements of 10Be Deposition Rates

      Nelson, D. E.; Korteling, R. G.; Southon, J. R.; Vogel, J. S.; Nowikow, I.; Ku, T. L.; Kusakabe, Masashi; Reyss, J. L. (American Journal of Science, 1983-01-01)
      A Tandem Van de Graaff accelerator has been modified for use in the direct measurement of natural abundances of 10Be and 14C. A description of the system is given and some 10Be results on oceanographic samples are discussed.
    • Technological Advances in the University of Washington Accelerator Mass Spectrometry System

      Farwell, G. W.; Grootes, P. M.; Leach, D. D.; Schmidt, F. H. (American Journal of Science, 1983-01-01)
      During the past year we have continued to work toward greater stability and flexibility in nearly all elements of our accelerator mass spectrometry (AMS) system, which is based upon an FN tandem Van de Graaff accelerator, and have carried out measurements of 14C/12C and 10Be/9Be isotopic abundance ratios in natural samples. The principal recent developments and improvements in the accelerator system and in our sample preparation techniques for carbon and beryllium are discussed, and the results of a study of 10Be cross-contamination of beryllium samples in the sputter ion source are presented.
    • Temporal 10Be Variations in Ice

      Beer, Jürg; Andree, Michael; Oeschger, Hans; Stauffer, Bernhard; Balzer, Richard; Bonani, Georges; Stoller, Christian; Suter, Martin; Wölfli, Willy; Finkel, Robert C. (American Journal of Science, 1983-01-01)
    • The Integration of Radiocarbon Dating in Archaeology

      Waterbolk, H. T. (American Journal of Science, 1983-01-01)
    • The Oxford Radiocarbon Accelerator Facility

      Gillespie, Richard; Hedges, R. E. M.; White, N. R. (American Journal of Science, 1983-01-01)
    • The Radon Problem in 14C Dating

      Nydal, Reidar (American Journal of Science, 1983-01-01)
      Due to traces of radium and uranium in most 14C samples, radon appears as a radioactive contamination in the CO2 prepared by combustion. This contamination must be removed by an active purification prodecure or by storing the CO2 prior to measurement. No effective electronic discrimination against radon and its daughter elements can be performed. The necessary storage time until radon has decayed varies widely, especially for marine shells. The latter material, collected from Norway and Svalbard, has been a main object for the present investigation. In a few cases, a measureable amount of radon may be left even after eight weeks. The behavior of radon and its daughter elements in a CO2 proportional counter has been studied.
    • The Reliability of Archaeologic Interpretation of Radiocarbon Dates

      Willkomm, Horst (American Journal of Science, 1983-01-01)
      14C dates of a medieval settlement with archaeologically well-dated strata are compared with the true ages of the respective layers. The 14C values indicate that each layer may contain older material reaching up to the beginning of settlement. Therefore, the 14C measurement of only a few wood or charcoal samples may lead to age estimations several hundred years too old.
    • The Unreliability of 14C Dates Obtained from Buried Sandy Podzols

      Geyh, Mebus A.; Roeschmann, Günter; Wijmstra, T. A.; Middeldorp, A. A. (American Journal of Science, 1983-01-01)
      A test for the reliability of 14C dating of soil was made at two sites with buried, autochthonous, and in parts, allochthonous sandy podzols, dated either lithoand pedostratigraphically or palynologically. The differences between the age ranges obtained and the apparent mean residence times (AMRT) calculated from the 14C content of alkaline extracts from fossil soil layers and horizons lean in organic matter exceed 10,000 years, corresponding to a maximum contamination with recent carbon of up to 50 %. The use of correction factors for the apparent mean residence times of podzols is not valid, not even for climate zones, because these values have a broad scatter for the same profile.
    • The Use of 14C in Natural Materials to Establish the Average Gaseous Dispersion Patterns of Releases from Nuclear Installations

      Otlet, M. L.; Walker, A. J.; Longley, H. (American Journal of Science, 1983-01-01)
      The Harwell Low Level measurements been measuring a variety of natural materials close to United Kingdom nuclear installations measurements are made first, to establish the releases to the atmosphere of 14C as observed tree rings and second, to establish dispersion contours ed over extended periods. The main study area has been Cumbria, around the BNFL nuclear installation at Sellafield. 14C, which can be measured to good precision even at values close to the normal natural levels, provides a powerful technique for the provision of practical experimental values much wanted for theoretical dispersion models.
    • Time History of Human Gallstones: Application of the Post-Bomb Radiocarbon Signal

      Druffel, Ellen M.; Mok, Henry Y. I. (American Journal of Science, 1983-01-01)
      Bomb-produced 14C is a valuable tool for studying rates of short-term processes involving carbon cycling. This study shows that bomb 14C is an excellent tracer of a biochemical process that takes place in the human body, namely the accretion of stones in the gallbladder. The methods developed for obtaining time histories of 14C/12C and 13C/12C in concentric layers from a large gallstone (30mm diameter) are reported. Formation times are assigned by matching the 14C/12C obtained from individual layers with those found for known-aged tree rings. Results show that the gallstone grew over a period of 10 years and seems to have lain dormant within the gallbladder for a period of 11 years. The average growth rate was 1.5mm/year.