The accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2001 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).

A new compact accelerator mass spectrometry (AMS) system dedicated to the measurement of radiocarbon has been commissioned at the Accium BioSciences headquarters in Seattle. The entire facility (including ancillary laboratories for the preparation of graphite targets) has been designed to handle samples with a wide range of 14C concentrations. In this paper, we discuss the technical details of the new facility and present performance test results demonstrating state-of-the-art capabilities. In particular, modern samples can be readily measured with 0.3% precision and accuracy, machine background levels are consistently in the low 10-16 (14C/12C), and chemical background is approximately equivalent to a fraction of modern of 0.004. In addition, when 100-times-modern samples were processed, no increase in background was observed, either during sample processing or during AMS measurement. This corresponds to a dynamic range for 14C analysis of 6 orders of magnitude.

The new facility Artemis was installed in 2003 in Saclay, France. This 3MV NEC Pelletron is dedicated to high-precision radiocarbon measurements for French 14C laboratories. We will present information on Artemis along with our sample preparation methods. Results from measurements on some intercalibration samples will be given along with the values of measured blanks. Finally, we report on some problems we have encountered when measuring sputter cathodes with high CH− outputs.

The accelerator mass spectrometry (AMS) facility at Seoul National University (SNU-AMS) was accepted in December 1998 and results reported first at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel, June 2000. At the Vienna conference, we reported our accelerator system and sample preparation systems (Kim et al. 2000). Recent developments of the AMS facility have been regularly reported at AMS conferences (Kim et al. 2001, 2004, 2007). Meanwhile, about 1000 unknown archaeological, geological, and environmental samples have been measured every year. In this report, the archaeological and geological data carried out in 2002 are presented in terms of years BP (before present, AD 1950), following the SNU-AMS date lists I and II published in Radiocarbon (Kim et al. 2006a,b).

We report on 2 recent developments in an ongoing program of characterizing and improving the National Electrostatics Corp. (NEC) MC-SNICS ion source at University of California (UC) Irvine's Keck AMS laboratory. First, we have investigated the possibility of modifying a large-body (134-sample) MC-SNICS to incorporate the UC Irvine Cs oven and vacuum-insulated Cs feed tube, which provide better confinement of Cs than the standard NEC setup. In our 40-sample source, the feed tube enters the source housing directly below the ionizer assembly. This area cannot be accessed for machining on the 134-sample source, but we have successfully tested a modified geometry where the delivery tube enters the body via the source end flange. Second, we recently installed a second beam profile monitor in the injection line of our spectrometer to allow us to make online emittance measurements. At full output (150 μA of C− at 55 keV), the emittance of our source at 8 kV sputtering voltage is approximately 40π mm mrad.

Fischer and Heinemeier (2003) present a hypothesis that the freshwater reservoir effect produces old apparent ages for radiocarbon dates run on charred cooking residues in regions where fossil carbon is present in groundwater. The hypothesis is based in part on their analysis of dates on charred cooking residues from 3 inland archaeological sites in Denmark in relation to contextual dates from those sites on other materials. A critical assessment of the dates from these sites suggests that rather than a pattern of old apparent dates, there is a single outlying date—not sufficient evidence on which to build a case for the freshwater reservoir effect.

In a paper published in Applied Radiation and Isotopes, Baffa et al. (2000) reported a Middle Holocene date (∼6.5 kyr BP) for a specimen of Toxodon platensis from Ribeira do Iguape, southeast Brazil, using the emergent technique electron spin resonance (ESR). Through an accelerator mass spectrometry (AMS) procedure applied on tooth collagen, we provide a new set of dates to test the accuracy of the ages generated by ESR. We obtained 2 dates more than 4500 BP older than the previous one, suggesting a minimum Late Pleistocene age for the specimen.

The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable currents of up to 6 μA C− out of gaseous samples with an efficiency of 3–6%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 3–30 μg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was <1 pMC.

We present a broad and detailed study of the background components of a liquid scintillation (LS) detector, using a simple laboratory-built system, ICELS. It was specifically designed for radiocarbon dating and is compact and easily transportable (total weight 35 kg). Its flexible LS detector unit has a dome-shaped vial with 3 mL benzene to which 45 mg butyl-PBD is added. The vial sits on the top of a vertical 28-mm-diameter phototube. The gamma radiation, to which the benzene is exposed under varying conditions, was measured by replacing the vial with a 38-mm-diameter Nal crystal. The pulse-height spectra of the 14C LS background and the Nal gamma background were measured in a surface laboratory and in a deep underground counting room with: 1) a lead shield of varying thickness; 2) lead of normal and low 210Pb concentration; 3) phototubes of 2 different types; and 4) varying benzene volume. The beta emission from the face of the tubes was measured with a low-level Geiger counter.

A preliminary investigation of the biocarbon fraction in carbon dioxide emissions of power plants using both fossil- and biobased fuels is presented. Calculation of the biocarbon fraction is based on radiocarbon content measured in power plant flue gases. Samples were collected directly from the chimneys into plastic sampling bags. The 14C content in CO2 was measured by accelerator mass spectrometry (AMS). Flue gases from power plants that use natural gas, coal, wood chips, bark, plywood residue, sludge from the pulp factory, peat, and recovered fuel were measured. Among the selected plants, there was one that used only fossil fuel and one that used only biofuel; the other investigated plants burned mixtures of fuels. The results show that 14C measurement provides the possibility to determine the ratio of bio and fossil fuel burned in power plants.

Progress in radiocarbon accelerator mass spectrometry (AMS) techniques enables much more access to wiggle-matching techniques for high-precision 14C dating with relatively low costs than before. Recently, we have applied wiggle-matching for a number of wood samples where dendrochronology is difficult because of various limitations imposed for dendro-dating. In most cases, wiggle-matching gave rather unambiguous calendar ages, but we found that in some cases the calibrated date was very sensitive to a systematic error of the 14C date. Here, we present a wooden artifact from the Ujishigai archaeological site as a case where the highest wiggle-matched date did not agree with the date given by dendrochronology. An age with lower probability agreed with the tree-ring age of AD 389, which marked the beginning of the production of Sue ware (unglazed stoneware) in Japan. We show that systematic errors must be carefully taken into account while interpreting 14C wiggle-matching results, whether they are due to instrumental errors (statistical) or due to a regional offset from the IntCal04 (Reimer et al. 2004) calibration curve.

We present the first results of an accelerator mass spectrometry (AMS) radiocarbon intercomparison program on 3 different charcoal samples collected in one of the hearths of the Megaceros gallery of Chauvet Cave (Ardèche, France). This cave, rich in parietal decoration, is important for the study of the appearance and evolution of prehistoric art because certain drawings have been 14C dated to the Aurignacian period at the beginning of the Upper Paleolithic. The new dates indicate an age of about 32,000 BP, which is consistent with this attribution and in agreement with the results from the same sector of the cave measured previously at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE). Six laboratories were involved in the intercomparison. Samples were measured in 4 AMS facilities: Center for Isotope Research, Groningen University, the Netherlands; the Oxford Radiocarbon Accelerator Unit, UK; the Centre de datation par le carbone 14, Univ. Claude Bernard Lyon 1, France (measured by AMS facilities of Poznań University, Poland); and the LSCE, UMR CEA-CNRS-UVSQ, France (measured by the Leibniz-Labor of Christian-Albrechts-Universität Kiel, Germany).

Development of radiocarbon analysis with precision better than 2% has the potential to expand the utility of 14CO2 measurements for carbon cycle investigations as atmospheric gradients currently approach the typical measurement precision of 2–5%. The accelerator mass spectrometer at Lawrence Livermore National Laboratory (LLNL) produces high and stable beam currents that enable efficient acquisition times for large numbers of 14C counts. One million 14C atoms can be detected in approximately 25 min, suggesting that near 1% counting precision is economically feasible at LLNL. The overall uncertainty in measured values is ultimately determined by the variation between measured ratios in several sputtering periods of the same sample and by the reproducibility of replicate samples. Experiments on the collection of 1 million counts on replicate samples of CO2 extracted from a whole air cylinder show a standard deviation of 1.7% in 36 samples measured over several wheels. This precision may be limited by the reproducibility of oxalic acid I standard samples, which is considerably poorer. We outline the procedures for high-precision sample handling and analysis that have enabled reproducibility in the cylinder extraction samples at the <2% level and describe future directions to continue increasing measurement precision at LLNL.

Recently, Bayesian statistical software has been developed for age-depth modeling (“wiggle-match dating”) of sequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is compared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agriculture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discuss future enhancements in Bayesian age modeling.