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β Unstable atomic nuclei with an excess of neutrons may undergo β− decay, where a neutron is converted into a proton, an electron and an electron-type antineutrino (the antiparticle of the neutrino): This process is mediated by the weak interaction. The neutron turns into a proton through the emission of a virtual W− boson. At the quark level, W− emission turns a down-type quark into an up-type quark, turning a neutron (one up quark and two down quarks) into a proton (two up quarks and one down quark). The virtual W− boson then decays into an electron and an antineutrino. Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors. Free neutrons also decay via this process. This is the source of the copious amount of electron antineutrinos produced by fission reactors. β Unstable atomic nuclei with an excess of Inverse beta decay is a key step in the fusion processes that produce energy inside the sun. Uses Beta particles can be used to treat health conditions such as eye and bone cancer, and are also used as tracers. The main element for these jobs is Strontium-90. Beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the beta radiation is absorbed while passing through the product. If the product is made too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the manufactured paper will then move the rollers to change the thickness of the final product. Inverse beta decay of a radioactive tracer isotope is the source of the positrons used in positron emission tomography. See also | ||||||||||
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