Fast-neutron heterogeneous scintillation detector with high discrimination of gamma background

Neutron detectors have been widely used for monitoring security and illicit transportation of nuclear and radioactive materials. Distinguishing feature of such application is the necessity to measure neutron flux caused by the monitored items that is close to the natural background flux. This paper examines potential improvement of characteristics of a multi-layer neutron detector with optic fiber sensors based on lithium-silicate (6Li) glass, by replacing the polyethylene layers with layers of hydrogen-containing scintillating plastic. Combination of two types of neutron-sensitive sensors enables two-phase discrimination of gamma background when measured in mixed n- and gamma-fields, by the amplitude and time criteria. The proposed heterogeneous scintillation detector has much higher gamma-background discrimination factor as compared to the existing examples of multilayered neutron detectors, while maintaining rather high neutron registration efficiency, typical for multilayered detectors.