Selective fast-neutron spectrometry

A procedure for measuring inelastic-scattering spectra of neutrons by coincidences of gamma quanta accompanying deexcitation of excited states of nuclei is described. The time resolution of the spectrometer is a function of the energy of the gamma quanta recorded and varies from 6 nsec for 122 keV to 1.2 nsec for 1.33 MeV. Experimental spectra for the reaction 56Fe (n, n' gamma) are presented. The gamma detector simultaneously selects events related to the excitation of a given nuclear state and provides a point of reference for the time-of-flight neutron spectrometer. The presence in the experimental spectra of several groups of neutrons allows determination of the direct as well as cascade population of the level in question