Radiocarbon dating facilities
Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 disintegrations per minute (0.05 µCi).Accelerator Mass Spectrometry (AMS) is a technique for measuring the concentrations of rare isotopes that cannot be detected with conventional mass spectrometers.The latter type of detector can measure both the total energy of the incoming ion, and also the rate at which it slows down as it passes through the gas-filled detector.These two pieces of information are sufficient to completely identify the ion as C atoms at the rate at which they decay.These are relatively low energies; the maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue.The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11.Current monetary exchange values can be estimated with the Universal Currency Converter.
Accelerating the ions to high energy has one more advantage.At the kinetic energies typically used in an AMS system it is possible to use well-established nuclear physics techniques to detect the individual C ions as they arrive at a suitable particle detector.This may be a solid-state detector or a device based on the gridded ionisation chamber.The original, and best known, application of AMS is radiocarbon dating, where you are trying to detect the rare isotope A nuclear particle accelerator consists essentially of two linear accelerators joined end-to-end, with the join section (called the terminal) charged to a very high positive potential (3 million volts or higher). Injecting negatively charged carbon ions from the material being analysed into a nuclear particle accelerator based on the electrostatic tandem accelerator principle. The negative ions are accelerated towards the positive potential.
At the terminal they pass through either a very thin carbon film or a tube filled with gas at low pressure (the stripper), depending on the particular accelerator.
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