DOE-HDBK-1019/1-93Atomic and Nuclear PhysicsINTERACTION OF RADIATION WITH MATTERRev. 0Page 67NP-01Interaction of Radiation with Matter SummaryAn alpha particle deposits a large amount of energy in a short distance of traveldue to its large mass and charge.Beta-minus particles interact with the electrons orbiting the nucleus of atoms,causing ionization by displacing the electrons. The beta particle loses energy witheach interaction. After the beta particle loses enough energy, it is captured in theorbital shells of an atom.Positrons interact with matter much the same way as beta minus particles. Afterthe positron has lost most of its energy by ionizing atoms, it is annihilated byinteraction with an electron. The electron-positron pair disappear and are replacedby two gammas, each with the energy equivalent of the mass of an electron (0.51MeV).Neutrons interact with matter by elastic scattering, inelastic scattering, orabsorption.Photoelectric effect is where a gamma interacts with an electron orbiting an atom.The entire energy of the gamma is transferred to the electron, and the electron isejected from its orbit.In Compton scattering a gamma interacts with an orbital electron, but only part ofthe gamma energy is transferred to the electron. The electron is ejected from itsorbit, and the gamma is scattered off at a lower energy.In pair-production, a gamma interacts with the electric field of a nucleus and isconverted into an electron-positron pair. The gamma must have an energy greaterthan 1.02 MeV for this to occur.SummaryThe important information in this chapter is summarized below.
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