Isotopic abundances of the elements xenon, krypton, and cesium formed in the 14-Mev neutron fission of 238U have been measured using the mass-spectrometric method. The relative yields of some isotopes of krypton, strontium, zirconium, molybdenum, ruthenium, iodine, xenon, barium, cerium and neodymium were measured using a Ge(Li) detector. The ratios were normalized through isobaric nuclides, and absolute yields were obtained by normalizing the sum of the heavy-mass yields to 100%. A semi-empirical method has been developed for constructing neutron yield curves. Such a curve was used to obtain a primary-yield curve from the cumulative yields reported here. The results indicate that considerable structure might exist in the primary-yield curve at the higher excitation energy. / Thesis / Doctor of Philosophy (PhD)

The ranges and stragglings of fission fragments from the thermal neutron fission of U-235 have been measured. Particular attention was given to the preparation of very thin uranium sources, the design of a well collimated recoil system and the preparation of the fragment catcher. The ranges and range distributions in aluminum of fission products of mass numbers 95, 140, 141 and 147 have been obtained. The range values obtained agree with previous determinations within the experimental error. The refined techniques developed in this work have enabled differential range distributions to be obtained which are more precise than any previous determinations. / Thesis / Master of Science (MSc)

Isotopic abundances of the elements barium, cerium, neodymium, samarium and europium formed in the thermal neutron fission of have been studied with a mass spectrometer. Suitable analyses of very young and old fission products have made possible the normaliza­tion of the isotopic abundances of each of these elements through iso­baric nuclides. In this manner the relative cumulative fission yield of every fission chain from mass 137 to 154 has been obtained. These yields, together with previously reported relative yields of masses 131 to 137 when normalized to total 100%, give the absolute cumulative yield of all the significant heavy fragment chains. The origin of the fine structure found in this mass yield distribution is discussed. It has been found that all fine structure can be explained in terms of a smooth primary mass-yield curve and a simple neutron distribution both of which are compared with experimental data from other laboratories. / Thesis / Doctor of Philosophy (PhD)

Isotopic abundances of the elements xenon, cesium, barium, cerium, neodymium, samarium, rubidium and strontium formed in the fast (fission spectrum) neutron fission of u^238 have been measured using the mass spectrometric method. These ratios were normalized 'With respect to each other through isobaric nuclides and isotope dilution to obtain the relative yields of isobaric chains in the heavy mass region. By normalizing the heavy mass yields to 100%, the absolute fission yields of twenty-one isobaric Chains in the 130 - 154 mass range were determined. The origin of the fine structure in the cumulative yield versus mass curve is discussed. It has been concluded that, while most of the fine structure arises from the variation in neutron emission probabilities, some of it could be the result of the shell effect in the fission process itself. / Thesis / Doctor of Philosophy (PhD)

No abstract provided. / Thesis / Master of Science (MSc) / Scope and contents: The probability of fission as a function of primary fragment velocities has been obtained by removing the neutron emission and instrumental dispersions from the velocities determined by Stein with time-of-flight techniques for the thermal neutron fission of u235. Each velocity was increased by 0.69% to make the average kinetic energy per fission agree with the calorimetric value of 167.1 Mev. Excitation energy distributions were obtained by using the primary fragment masses given by Cameron and assuming that the most probable charge distribution for a given mass ratio i s that which leads to the greatest energy release. Evaporation theory was used to determine the number of prompt neutrons emitted. When the excitation energy is divided equally between the fragments and a nuclear temperature of 0.59 Mev is used, the average number of neutrons emitted is 2.95 per fission.