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Pulse shape discrimination in plastic scintillators has been of much interest in recent years. As with many innovative technologies, initial formulations for PSD plastics provided new capabilities that required much in-depth research to fully develop and refine. Herein we describe results from extensive optimization studies which have led to the development of PSD plastics with markedly improved scintillation performance and physical properties. Results of exploring different plastic matrices as well as a variety of secondary dyes are reported and optimum components are described. Due to the large concentration of additives required to manifest optimal PSD properties in plastic scintillators, the physical stability can be limited and the mechanical properties of PSD plastics are inferior to standard engineering plastics. Practical and theoretical solutions have been developed to address the physical stability and mechanical deformation problems in PSD plastics, and this work has resulted in physically stable scintillators with robust mechanical properties. Performance deterioration on increasing the size of PSD plastics is also addressed. At large sizes, physical and performance characteristics are much more sensitive to preparation conditions and compositional alterations as compared with small scintillators, and efforts to improve these properties are described. Finally, efforts to incorporate aromatic lithium compounds into PSD plastics are summarized and the effects of the lithium compounds on scintillation, stability, and attenuation are discussed.
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