Fabrication and characterization of a lithium-glass-based composite neutron detector

A novel composite, scintillating material intended for neutron detection and composed of small (1.5 mm) cubes of KG2-type lithium glass embedded in a matrix of scintillating plastic has been developed in the form of a 2.2 in.-diameter, 3.1 in.-tall cylindrical prototype loaded with (5.82±0.02)% lithium glass by mass. The response of the material when exposed to 252Cf fission neutrons and various γ-ray sources has been studied; using the charge-integration method for pulse shape discrimination, good separation between neutron and γ-ray events is observed and intrinsic efficiencies of (1.15±0.16)×10−2 and (2.28±0.21)×10−4 for 252Cf fission neutrons and 60Co γ rays are obtained; an upper limit for the sensitivity to 137Cs γ rays is determined to be <3.70×10−8. The neutron/γ discrimination capabilities are improved in circumstances when a neutron capture signal in the lithium glass can be detected in coincidence with a preceding elastic scattering event in the plastic scintillator; with this coincidence requirement, the intrinsic efficiency of the prototype detector for 60Co γ rays is (2.42±0.61)×10−6 while its intrinsic efficiency for unmoderated 252Cf fission neutrons is (4.31±0.59)×10−3. Through use of subregion-integration ratios in addition to the coincidence requirement, the efficiency for γ rays from 60Co is reduced to (7.15±4.10)×10−7 while the 252Cf fission neutron efficiency becomes (2.78±0.38)×10−3.