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Plastic Scintillators for Pulse Shape Discrimination of Particle Types in Radiation Detection

  • Author(s): HAJAGOS, TIBOR JACOB
  • Advisor(s): Pei, Qibing
  • et al.
Abstract

Organic scintillators have a long history in the field of radiation detection, dating back to some of the earliest studies of organic photophysics and optoelectronic properties. In particular, plastics have come to dominate the commercial market for organic scintillators, due to their low cost and ease of use and manufacturing, and more notably in spite of their poorer performance in many metrics. While there has been decades of active research since their inception, little progress has been made to improve upon the now well established compositions of commercial plastics, a notable exception being the recent development of plastic scintillators capable of pulse shape discrimination (PSD) of n/γ radiation, which is of particular interest among governments and industry for the detection of illicit nuclear material and weapons. In recent years, much attention has been paid towards the study of luminescent organic materials, in particular due to the invention and widespread adoption of organic light emitting diode (OLED) based electronic devices, and the knowledge and lessons that have been fundamental to such fields have recently begun to be adopted by the organic scintilator community. In this work, new approaches to the design of both plastic scintillator components, and of the materials as a whole, are described, with particular emphasis paid towards the design and synthesis of small molecule scintillating dyes that are specifically tailored towards the development of PSD-capable plastic scintilators. In the first of these approaches, the design and synthesis of a highly soluble and polymerizable derivative of 9,10-diphenylanthracene is described, and the properties of plastic scintilators fabricated from this dye when copolymerized with poly(vinyl toluene) were investigated. This particular approach was used to demonstrate a proof-of-concept of PSD in highly loaded plastics stabilized through copolymerization of the primary dye, a strategy conceived to address the particular shortcomings of the current generation of PSD plastics. The second general approach investigated is the application of the phenomenon of thermally activated delayed fluorescence (TADF) — most notably a key innovation among the latest developments in OLED technologies — to the enhancement of the performance of organic sicntillators. Several key observations about the potential and efficacy of TADF dyes as novel organic scintillators were made, including a demonstration of the profound effects the the TADF phenomenon can have on scintillation properties. These findings suggest that it is quite possible that TADF dyes could eventually enable an entirely new generation of high performance organic scintillators, and PSD-capable plastics in particular.

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