On the reconstruction of the time-resolved energy spectrum for short-pulsed neutron sources

New insights into the fusion reaction mechanism of the hot dense plasmas can be obtained if the time-resolved neutron energy spectrum of short-pulsed emitted neutron is determined. Its main objective is to obtain information about the production mechanism leading to the observed neutron produced by D-D reactions. The fusion systems provide up to 1012 neutrons per discharge with an emission time in the range 50 to 500 ns. None of the existing standard spectroscopy methods gives satisfactory results for these neutron pulses. Therefore an extended time-of-flight method was suggested. It was also demonstrated that the problem can be treated as a tomographic one if the energy scale is changed into a reciprocal velocity. A maximum likelihood tomographic method is used to reconstruct this spectrum. The performances of the algorithm were studied using a phantom (simulated time and energy distribution) with multiple spikes (three). High-level and medium level time and energy resolution values can be watched by the shifts and gaps between spikes and by the size of spikes. The three spikes are of equal height and of rectangular shape in order to evaluate the shape distortion due to the limited view angle domain. A flight base of 80 m, practicable in real experiments, and detectors placed at 0, 5, 10, 15, 20, 30, 45 and 80 m were considered. Good reconstruction are obtained and a high-level of resolution is ensured. The method is not sensitive to the noise of experimental data due to the fact that it incorporates an estimation procedure depending on the statistical nature of noise in measurements. (authors)