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Neutron vision

From New Orleans, at a meeting of the American Physical Society

A new technology for measuring neutrons might help detect smuggled radioactive materials.

A common type of neutron detector uses a container filled with helium-3, a light isotope that readily reacts with neutrons. When a neutron from a sample of uranium, for example, hits a helium-3 nucleus, a reaction ensues. The helium nucleus breaks and produces one hydrogen nucleus (a proton) and an atom of hydrogen's radioactive isotope, tritium. Usually, these particles are highly energetic and ionize matter. In the presence of a voltage, the ionization produces a small spark, and the reaction is detected.

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