It can take up to six months to have a sample tested.
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. Because carbon-14 decays over time, the amount of it in a sample indicates the age of the sample.How much their path bends depends on their mass: Lighter ions bend more. Penn State will soon be home to an accelerator mass spectrometer (AMS) that will allow researchers all over the country to do high-precision carbon dating to address questions about Earth's past and present.It will enable precise dating of carbon-containing material with ages stretching back over the past 50,000 years." "This new facility will improve our ability to study human-environmental interactions where chronology is key," adds Kennett."It will be helpful in areas where we really need to know the order of events." For example, mammoths went extinct near the end of the last Ice Age, but whether the changing climate, disease, humans, or a comet impact did them in is a matter of debate that might be resolved with more precise dating techniques.By measuring the ratio of carbon-14 to the other isotopes of carbon in a sample, researchers can determine that sample's age.
The precision of Penn State's new instrument is impressive; it will be able to determine the age of samples from the past 10,000 years within 15 to 20 years.
After thorough cleaning, a small amount of the material is vacuum-sealed in a quartz tube, which is then heated to a high temperature to convert the material to carbon dioxide, water, and nitrous oxides.
Kennett currently directs the Human Paleoecology and Isotope Geochemistry Laboratory in the Department of Anthropology, where materials are prepared for carbon-14 analysis.
This isotope has six protons and eight neutrons and, crucially, is radioactive; over time, it decays to nitrogen-14 (with seven protons and seven neutrons).
The half-life of carbon-14 is about 5,730 years, which means it takes that long for half the radioactive C atoms in a substance to decay.
For scientists whose test material is rare, valuable, or extremely hard to collect, that's important.