This work proposes a simple neutron energy spectroscopy based on a single long lithium- or boron-doped scintillator coupled to two photo-electronic devices (PMTs) on both ends. The principle is that the neutron’s capture position [depth of interaction (DOI)] inside the scintillator is connected with the incident energy. The performance of the spectroscopy was simulated using the Geant4 package. The DOI inside the scintillator, as well as the light output ratio (LR) of the two PMTs, were acquired, then the relationship between the DOI and LR at various incident neutron energy was calculated. These calculations were further used as the neutron response function for the spectroscopy.

A spectroscopy that is sensitive to neutrons within 10 eV to 10 keV was designed that could be applied for the neutron spectrum detection of boron neutron capture therapy (BNCT). The GRAVEL algorithm and the maximum likelihood expectation maximization algorithm were used to unfold the neutron spectrum, the mean-square-error (MSE) for monoenergetic neutrons was about 0.05 and the MSE for the continuous BNCT spectrum was about 0.08, which showed a remarkable technical advantage and feasibility.