Thermal Neutron Scintillator Detectors Based on Poly (2-Vinylnaphthalene) Composite Films

A series of novel 6 Li-loaded plastic scintillation films have been designed and fabricated to detect thermal neutrons. Organolithium salts containing enriched 6 Li were synthesized and interspersed in a series of matrices comprising a polymer doped with an antenna fluor. Thermal neutron capture by 6 Li produces charged particles with kinetic energy which is sufficient to ionize and excite the polymeric matrix. This energy is collected by the antenna fluor, which produces a photonic response detectable by a photomultiplier tube. Design and optimization of these scintillation films is discussed herein. A current problem in the design and fabrication of polymeric composite materials is phase separation. The matrix is a low-dielectric aromatic polymer; hence, ionic molecules in the composite tend to phase-separate from the matrix and produce agglomerates which decrease the quantum efficiency by scattering and/or quenching the photonic response to thermal neutrons. Based on the experimental results, the importance of synthesizing polymers with high quantum yield and efficiency in energy migration and transport for making effective composite neutron scintillators is emphasized.