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In order to use inelastic neutron scattering to isomeric levels as a tool in evaluating nuclear strength functions, we derive the appropriate evaporation formulae; both with and without corrections for the statistical fluctuations of the compound nucleus reduced partial widths. The isomeric activity induced by inelastic neutron scattering is calculated for: In¹¹⁵, Rh¹º³, Y⁸⁹ and Nb⁹³; and is used to illustrate the effect of the fluctuation corrections and the level spin and parity assignments, on the calculated cross sections. Comparison with experimental data is used to infer probable assignments of level spins and parities for In¹¹⁵ and Rh¹º³. We also show that for any nucleus lying near an even or odd partial wave strength function resonance, the inelastic neutron scattering cross section to isomeric levels will be directly proportional to l ≥ 2 strength functions. In the examples cited above, it is the d-wave strength function; and the isomeric cross section shows the corresponding dependence on the optical model potential, being directly proportional to the strength of the imaginary part and insensitive to the real part of the potential. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An Optical Model study has "been made for the elastic scattering of 4.2 MeV. neutrons from three heavy nuclei, Lead, Bismuth and Uranium. The Optical Model used included a real, imaginary, and spin-orbit potential well. Its parameters were determined from a least square fitting to the experimental scattering data available in the literature for angles from 15 to 180 degrees. The model is then used to estimate the nuclear scattering to be expected at small scattering angles. It is shown that Schwinger scattering and incident neutron polarization significantly alter the shape of the elastic cross section at angles less than 10 degrees. At 5 degrees this change is about 3%. Additional effects due to Electric Polarizability scattering are shown to be very small and not sufficient for a determination of the polarizability of the neutron from the elastic scattering data at this energy. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Global climate change in either the form of global warming or global cooling is occurring relatively rapidly today. Studies have shown that increased levels of greenhouse gases, especially atmospheric carbon dioxide (CO₂) are the dominate component contributing to the change. A reduction in CO₂ may be influenced by making larger efforts to sequester carbon in soil and therefore to not only keep soil organic carbon (SOC) levels steady but by possibly increasing them through human assistance. Soil sequestration of carbon has been estimated to have one of the largest potentials to sequester carbon in the world. By some estimation up to 2 billion tons of carbon can be sequestered terrestrially. Therefore the efficient and repetitive monitoring of SOC on a local and global scale is a critical issue. The current soil measurement technique utilized around the world is chemical analysis of one form or another. Chemical analysis of soil is a well studied technique that returns relatively accurate results of density, moisture content, and elemental breakdown of a soil. However, chemical analysis is costly, time consuming, and destructive. As a result of the destructive nature of soil chemical analysis, repeated measurements of the same soil site is impossible. Also, due to time constraints, it would be difficult to analyze a large area utilizing chemical analysis. To surmount the inherent issues with chemical analysis a system based on inelastic neutron scattering (INS) is under development for non-destructive monitoring of carbon in soil. It is based on spectroscopy of gamma rays induced by fast (14 MeV) neutrons emanating isotropically from a D-T neutron generator (NG). The calibration of the INS system is a remains a challenge. Calibration of the system is necessary for relating the carbon gamma ray counts from the detectors to a carbon concentration in the soil volume measured. Utilizing a benchmarked Monte Carlo model of the INS system it is possible to create many calibration curves. The advantages of the model are that the calculations require a relatively short amount of time, and that all the soil variables are defined by the user.

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