Study of cross-talk shielding in a fast neutron multiplicity counting system

In Fast Neutron Multiplicity Counting (FNMC), neutron cross-talk caused by elastic scattering between two or more detectors is unavoidable, posing a critical challenge to the accuracy of FNMC. This study focuses on an FNMC apparatus composed of liquid scintillator detectors, investigating the impact of polyethylene neutron scattering structures on first- and second-order cross-talk rates. By analyzing the position and energy distribution of neutrons scattered within detectors and incident onto adjacent detectors, targeted polyethylene structures were designed to minimize crosstalk rates within the system. Calculations were conducted on shielding structures of various sizes and positions to achieve optimal neutron crosstalk suppression under specific detector layout conditions. Experimental validation confirmed the reliability of Geant4 simulation results and the effectiveness of the polyethylene shielding structures. Through simulations conducted on a 1 × 8 detector system composed of 3-inch EJ-301 liquid scintillator detectors, it was found that the implementation of shielding structures significantly reduced cross-talk rates across all orders.