Atomic and Nuclear PhysicsDOE-HDBK-1019/1-93NEUTRON INTERACTIONSElastic scattering of neutrons by nuclei can occur in two ways. The more unusual of the twointeractions is the absorption of the neutron, forming a compound nucleus, followed by there-emission of a neutron in such a way that the total kinetic energy is conserved and the nucleusreturns to its ground state. This is known as resonance elastic scattering and is very dependentupon the initial kinetic energy possessed by the neutron. Due to formation of the compoundnucleus, it is also referred to as compound elastic scattering. The second, more usual method,is termed potential elastic scattering and can be understood by visualizing the neutrons andnuclei to be much like billiard balls with impenetrable surfaces. Potential scattering takes placewith incident neutrons that have an energy of up to about 1 MeV. In potential scattering, theneutron does not actually touch the nucleus and a compound nucleus is not formed. Instead, theneutron is acted on and scattered by the short range nuclear forces when it approaches closeenough to the nucleus.InelasticScatteringIn inelastic scattering, the incident neutron is absorbed by the target nucleus, forming acompound nucleus. The compound nucleus will then emit a neutron of lower kinetic energywhich leaves the original nucleus in an excited state. The nucleus will usually, by one or moregamma emissions, emit this excess energy to reach its ground state. Figure 17 shows theprocess of inelastic scattering.For the nucleus that has reached its ground state, the sum of the kinetic energy of the exitFigure 17 Inelastic Scattering neutron, the target nucleus, and the total gamma energy emitted is equal to the initial kineticenergy of the incident neutron.Rev. 0Page 45NP-01
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