Induced Fission Studies of 235U and 239Pu

New experiments to study the basic fission process have been performed using an array of high purity germanium detectors. The radiation observed is emitted from the prompt fission fragments, and the fission is induced with a thermal neutron beam at the Intense Pulsed Neutron Source of Argonne National Laboratory. Data from targets of 235U, 239Pu, and 233U have been collected during several week runs over the past two years. Data collection from these targets is part of an ongoing study of the basic fission process. Historically, the fission process was studied by examining the fission fragments that were produced by slow beta decay. While these studies have provided much of the existing fission knowledge, they offer little insight into the prompt fission process itself. By contrast, the reported experiments examine the fission fragment decay in the first moments (10-22 seconds) following fission. It is seen that the fragments are populated at significantly higher energies than was previously reported. By using fast coincidence methods in conjunction with large detector arrays, the current studies can investigate new decay modes, gamma-ray signatures, radiation multiplicity, and prompt fission yields. The current studies are also of interest to applied research of fissile material disposition and storage. Particularly, the experimental technique discussed provides an unambiguous way to identify unknown fissile material. Preliminary results will be presented from the analysis of 235U and 239Pu data. These results will include prompt fission fragment yields and a discussion of the incoming neutron contribution to the fission process. Also the method of identification of the fissioning isotopes will be discussed.