Detection of actinides via nuclear isomer de-excitation

Graduation date: 2010The detection of illicit weapons-grade nuclear material is a significant technical challenge receiving a great deal of attention in the nuclear community. A proposed solution is to actively bombard the material under investigation with neutrons, populating nuclear isomers in any potential fissile material. These isomers decay quickly, releasing gamma rays that have a higher energy than those from natural radioactive decay, significantly increasing the probability of detection.\ud \ud This research covers an experiment related to the Actinide Isomer Identification project (AID). The AID project is the investigation of an active interrogation technique that utilizes nuclear isomer production, with the goal of assisting in the interdiction of illicit nuclear materials. In an attempt to find and characterize isomers belonging to 235U and its fission fragments, a 232Th target was bombarded with a monoenergetic 6Li ion beam, operating at 45 MeV.\ud \ud The experimental data was gathered using an array of silicon, high purity germanium (HPGe) and bismuth germanate (BGO) radiation detectors. The silicon detectors were used to detect reaction products, which were used to start a\ud clock to time gamma ray interactions in the HPGe detectors. The BGO detectors were used to filter out Compton scatter events and background signals.\ud \ud The data was processed with the spectroscopic software gf3m to identify the signals originating from isomers. The analysis led to the identification and characterization of 19 isomers, of which several were recognized as useful to the goals of the AID project