Simulation Study of Fast, High-Z, High-Transparency Nanocomposite Organic Scintillators for use in Timing Radiation Detectors

Organic scintillators traditionally had limited use for x-ray and gamma ray detection because of their low stopping power. In addition, because of the near absence of photoelectric interactions they lack spectroscopy capabilities. Recent advances in material engineering have made it possible to efficiently embed high atomic number elements within plastic while retaining high transparency to light. These nanocomposite materials hold the promise of combining the fast rise and decay times of organic scintillators with the higher density, efficiency and photofraction of traditional inorganic scintillators. Furthermore, such nanocomposites are easily scalable to significant volumes without the difficulties involved with growing large inorganic crystals. Here we examine in simulation the expected response to gamma radiation of several new nanocomposite scintillators under development at UCLA. Three high-Z composites are studied: CdxZn1-xS/ZnS (CZS) which is a self-luminescent quantum dot (QD) and HfO2 and YbF3 which are non-luminescent high-Z compounds. The response of these nanocomposites loaded in plastic at several weight percentages are compared to common organic and inorganic scintillators: NE102 and LYSO. The coincidence timing response (CTR) will depend on the measured rise (τr) and decay (τd) times of these scintillators as well as the light yield (LY) and collection efficiency (ε) of a photo detector. Here we report on the photofraction and efficiency as determined through simulation and discuss our plan to measure CTR for these scintillators.