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CROSS SECTIONS OF THE FISSION OF U$sup 235$ INDUCED BY INTERMEDIATE ENERGY HELIUM IONS (thesis)

Technical Report ·
OSTI ID:4283357
A detailed study of fission was made so that the experimentally obtained tctal cross section for compound nucleus formation could be compared with theory and so that the fine structure features of fission could be When the form and size of a reactor are given, the neutron flux distribution is known and consequently the heat source distribution. The steady-state temperature examined. U/sup 235/ was irradiated with 20 to 40 Mev helium ions. The fission products were separated radiochemically and assayed in calibrated 2 pi proportional flow and Nal(Tl) crystal scintillation counters. Fission studies made at 39.9, 33.8, 28.2, 23.1, and 20.5 Mev showed several features of fission: The fission is predominately asymmetric with the symmetric mode increasing rapidly throughout the range. The cross section data obtained corresponds to compound nuclear theory using a radius parameter of r/ = 1.5 x 10/sup -13/ cm. As previously observed for other nuclides, the valley to peak ratio of fission can be related to the excitation energy of the compound nucleus. A fewer number of neutrons emitted per fission is found than previously reported. Other features of fission such as shell effects and the ''primary'' or ''independent'' yield problem are also discussed. The appendices contain information on the chemistry separation-schemes, the 4 pi beta - gamma coincidence methed and the self-absorption, backscattering and geometry factors of a 2 pi beta proportional flow counter for several fission nuclides. (auth)
Research Organization:
Purdue Univ., Lafayette, Ind.
NSA Number:
NSA-13-010387
OSTI ID:
4283357
Report Number(s):
AECU-4044
Country of Publication:
United States
Language:
English

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