JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY
Dating archaeological organic material depends on the amount of the radioactive carbon-14 isotope present, which decreases with the length of time since it ceased to exchange carbon with the surrounding atmosphere. In the Accelerator Mass Spectrometer (AMS) used at the Oxford Radiocarbon Accelerator Unit the predominant stable isotopes carbon-12 and carbon-13 are counted by the electrical current they generate, displayed in pico-amperes, whilst the carbon-14 detector flashes a separate signal, as a red flashing light above the C13 display as a radioactive isotope is identified. These displays show that the separate detectors are functioning, Photographed at the Oxford Radiocarbon Accelerator Unit, University of Oxford, UK.
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