AMS_diagram

AMS_diagram

how an accelerator mass spectrometer works

An accelerator mass spectrometer measures the amounts of different isotopes within a sample. For carbon dating, the process starts in an ionizing chamber, where the atoms within a sample of pure carbon are given a negative charge. An accelerator then increases the kinetic energy of the carbon ions to 10-30 million electron volts and moves them through a tube where a powerful electromagnet makes them change direction. How much their path bends depends on their mass: Lighter ions bend more. This separates the three isotopes of carbon. A detector measures the amount of each isotope. Because carbon-14 decays over time, the amount of it in a sample indicates the age of the sample.

IMAGE: Eric S. Taylor, WHOI Graphic Services