A method for neutron-induced gamma spectra decomposition analysis based on Geant4 simulation

In various monitoring and detection tools that use pulsed neutron generators as radiation sources, the gamma rays induced by the interaction with various nuclei at different stages of neutron transport can reflect information about the medium. These gamma rays are generated in two major interactions: inelastic scattering of fast neutrons and radiative capture of thermal neutrons, corresponding to the inelastic and capture gamma rays, respectively. However, the two types of gamma rays that reflect different properties of the medium are difficult to collect by normal detectors independently. The proportion of the two gamma rays needs to be solved for the separation of inelastic and capture gamma. Therefore, this study proposes an optimized spectra decomposition method to calculate the inelastic-to-capture ratio in the measured total gamma spectra based on the net inelastic and capture spectra obtained using the Geant4 simulation. Because the simulated data cannot reflect the energy resolution of the measured spectra, we introduce the Gaussian broadening function of the gamma detector while calculating the proportion of the spectra components, and achieve optimization of the proportion values and resolution parameters simultaneously. Based on the results, the total simulated spectra obtained by superimposing the broadened net inelastic and capture gamma spectra according to the calculated inelastic-to-capture ratio are in good agreement with their measured counterpart.