JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY JAMES KING-HOLMES / SCIENCE PHOTO LIBRARY
A wheel of graphite pellets contained in aluminium 'targets' are loaded into the Accelerator Mass Spectrometer (AMS) for radiocarbon dating of organic archaeological samples. Each one is pushed into the operating position where it is converted to negative carbon ions by bombarding it with caesium ions. The carbon ions are injected into the AMS where the relative proportions of the carbon isotopes present are measured. As the carbon-14 isotope portion decreases with age, the date when the original plant or animal ceased to absorb it by death or decay, can be measured.
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