Inelastic neutron scattering from silicon
Tabony, Robert Henry
Bonner, T. W.
Master of Arts
In order to have a better understanding of the atomic nucleus, a variety of nuclear reactions should be studied. One particular type of nuclear reaction is the inelastic neutron scattering from an element, that is, the observation of neutrons scattered from an element which have less energy leaving than when entering the scattering element, the rest of the energy having caused nuclei to be in some excited state. If the excited states in a nucleus are not too near each other, then one can observe the inelastic neutron cross section over a given incident neutron energy range indirectly by observing the gamma rays produced at energies corresponding to these states; this is both easier and much more accurate than the direct observation of the inelastically scattered neutrons. Silicon is a very satisfactory element for this type of investigation, since the lowest energy level in Si28 is 1.78 Mev, while the next level is about 4.54 Mev. Natural silicon is 92.2% Si28, 4.7% Si29, and 3.1% Si30. Hence the effect of the Si and Si is small. In this experiment, the relative inelastic neutron cross section was observed over an incident neutron energy range of 1.6 to 4.5 MeV by counting the gamma rays from the lowest Si28 level. At certain higher energies, the twenty channels were set so as to observe any peaks produced by gamma rays from levels above 1.78 Mev.