Measurement of Prompt Fission γ-ray Spectra in Fast Neutron-induced Fission

Abstract

Knowledge of prompt fission γ-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission γ-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the γ-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other γ-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the 27Al(p,γ) reaction. First prompt fission γ-ray spectrum measurements performed for the spontaneous fission of 252Cf and for 1.7 and 15.6 MeV neutron-induced fission of 238U at the CEA, DAM, DIF Van de Graaff accelerator, will be presented.