(麻省理工)Q方程式、弹性散射运动学.pdf.pdfVIP

22.101 Applied Nuclear Physics (Fall 2004) Lecture 16 (11/12/04) Neutron Interactions: Q-Equation, Elastic Scattering _______________________________________________________________________ References: R. D. Evan, Atomic Nucleus (McGraw-Hill New York, 1955), Chap. 12. W. E. Meyerhof, Elements of Nuclear Physics (McGraw-Hill, New York, 1967), Sec. 3.3. ________________________________________________________________________ Since a neutron has no charge it can easily enter into a nucleus and cause reaction. Neutrons interact primarily with the nucleus of an atom, except in the special case of magnetic scattering where the interaction involves the neutron spin and the magnetic moment of the atomic. Since we will not consider magnetic scattering in this class we can neglect the interaction between neutrons and electrons and think of atoms and nuclei interchangeably. Neutron reactions can take place at any energy, so one has to pay particular attention to the energy dependence of the interaction cross section. In a nuclear -3 7 reactor neutrons with energies from 10 ev (1 mev) to 10 ev (10 Mev) are of interest, 10 this means we will be covering an energy of 10 . For a given energy region – thermal, epithermal, resonance, fast – not all the possible reactions are equally important. What reaction is important depends on the target nucleus and the neutron energy. Generally speaking the important types of interactions, in the order of increasing complexity from the standpoint of theoretical understanding, are: (n,n) – elastic scattering. There are two processes, potential scattering which is neutron interaction at the surface of the nucleus (no penetration) as in billia