This paper deals with time-of-flight diagnostics of relatively short neutron pulses from tens to hundreds of nanoseconds. The aim is to determine the time evolution of energy spectra. The diagnostic setup consists of several neutron detectors placed in one direction at different distances. This approach is improved by placing additional detectors in the opposite direction. How the reconstruction method works with two opposite directions is explained in this paper. Improvement is limited to the deuterium fusion reaction D(d,n)3He. However, the principles described here could be applied in various fusion experiments. The advantage of our approach is not only better reconstruction but also the partial elimination of the influence of scattered neutrons. The described method was applied in the processing of data from fusion experiments in the PF-1000 facility and provided time evolution of the neutron energy spectra with energy resolution of 50 keV. In these plasma-focus experiments, results indicated a non-thermal production mechanism of the predominant part of the neutrons produced.
Real-time diagnosis of ion temperature by neutron yields in magnetic confinement fusion