Experimental Measurements of Prompt Fission Gamma Ray Spectra

Prompt fission Gamma Ray Spectra (PFGS) play an important role in understanding the de-excitation process of newly formed nuclei produced from fission. This study focuses on PFGS produced from photofission, as previous research primarily utilized neutron-induced or spontaneous fission. Fission was induced in Uranium-238 targets at the High Intenity gamma-ray Source (HIgS) and the resulting gamma rays were measured using LaBr and CeBr detectors. The PFGS are convoluted within the detector response, so the experimental spectra must be deconvoluted to report the true PFGS from photofission. Additionally, multiple offline analysis techniques were investigated to determine the best method of producing the gamma-ray spectra from the dataset. This includes a pulse-height analysis, a moving average waveform analysis, a pulse integration analysis, and the rejection of pulse pile up events. This work concluded that the pulse integration method provided the lowest resolution within the spectra. Pile up events were found at rates of 2-3% for the calibration data, and 6-8% percent for the fission data. Results for PFGS are preliminary and further work is being carried out to deconvolute the experimental fission gamma-ray spectra. This includes using a detector response matrix to reconstruct the experimental spectra, reporting the true PFGS in the process. This measurement of PFGS produced from photofission and can be used to better model the fission process.