Measurement of the prompt fission gamma-ray spectrum of Pu-242

The prompt gamma-ray spectrum of fission fragments is important in understanding the dynamics of the fission process, as well as for nuclear engineering in terms of predicting the gamma-ray heating in nuclear reactors. The gamma-ray spectrum measured from the fission fragments of the spontaneous fission of Pu-242 will be presented here. A fission chamber containing in total 37mg of Pu-242 was used as active sample. The gamma-quanta were detected with high time-and energy-resolution using LaBr3 and HPGe detectors, respectively, in coincidence with spontaneous fission events detected by the fission chamber. The acquired gamma-ray spectra were corrected for the detector response using the spectrum stripping method. About 70 million fission events were detected which results in a very low statistical uncertainty and a wider energy range covered compared to previous measurements. The prompt fission gamma-ray spectrum measured with the HPGe detectors shows structures that allow conclusions about the nature of gamma-ray transitions in the fission fragments. The average photon multiplicity of 8.2 and the average total energy release by prompt photons per fission event of about 6.8 MeV were determined for both detector types.