Determination of fast neutron spectrum using recoil-proton track imaging method

Abstract

High sensitivity and good neutron/gamma discrimination, as well as online determination, are goals that researchers are pursuing for fast neutron spectrum measurements (FNSM). For this purpose, we are attempting a novel approach based on the recoil-proton track imaging (RPTI) method to do FNSM. The RPTI neutron spectrometer has been designed and built, and it mainly consists of a polyethylene foil for converting neutrons to protons, a gas scintillation chamber for generating photons along the recoil proton track, and a scientific camera system for recording the track photons in real time. Proof-of-principle experiments have been performed with the RPTI neutron spectrometer at a DT neutron generator at China Institute of Atomic Energy. As a result, numerous recoil proton track images at the single-particle level were successfully acquired and revealed in real time. Also, the proton tracks can be clearly distinguished from the background in the track images, indicating good signal-to-background ratio of the system. Particularly, both the proton ranges and the Bragg curve peak positions can be extracted online from the track images, which can lead to online generation of DT neutron spectra. These results show promising performance of the novel fast neutron spectrometer, which will bring significant advantages in various applications.