A Compact System for Continuous-flow Accelerator Mass Spectrometry

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

0321045 Hayes This Major Research Instrumentation award to Woods Hole Oceanographic Institution (WHOI) in Massachusetts provides funds for development of a compact, continuous-flow, accelerator mass spectrometer, designed specifically for monitoring levels of 14C (radiocarbon) relative to other carbon isotopes in a continuously flowing gas stream. The instrument will respond significantly (signal/noise = 3) to concentrations of radiocarbon ten-fold lower than those in the modern atmosphere in samples as small as one microgram carbon. It will be capable of continuously analyzing chromatographic effluents and of determining the abundance of 14C in individual chromatographic peaks. Previous work has demonstrated that surveys of radiocarbon distribution within individual organic compounds from natural samples can reveal the sources of those compounds, and this new instrument will make it possible to extend those results to a wide variety of compounds in diverse samples, addressing important questions about carbon cycling in natural environments. Specific initial planned applications include study of releases of carbon dioxide to the atmosphere and the reconstruction of ancient climates. Research on hydrocarbon cycling will take advantage of the lack of radiocarbon in fossil hydrocarbons, thus providing a strong negative tracer for petroleum and other pollutants in natural environments. The instrument will be constructed from two large magnets, a particle accelerator, an electrostatic deflecting system and a particle-counting detector in addition to a microwave ion source, a key subsystem that uses microwave energy to create a plasma from which positive carbon ions can be extracted. A prototype of the microwave ion source has been built and tested previously at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility at WHOI. The new instrument will be housed in a new laboratory being constructed to allow expansion of NOSAMS, and managed as part of that facility. Once built, it will be operated as a shared-use facility for qualified, federally-funded researchers and others, similar to the existing accelerator mass spectrometer at NOSAMS. This instrumentation award is supported by the Division of Ocean Sciences at NSF. Woods Hole Oceanographic Institution provides cost sharing support from non-federal funds. ***