Organic Glass Scintillators for Nuclear Physics Experiments

Neutron detectors such as the Low-Energy Neutron Detector Array (LENDA) at the Facility for Rare Isotope Beams (FRIB) at Michigan State University play an important role in the understanding of the structure of exotic nuclei, the Weak Interaction, and the Equation of State. Discoveries about the properties of exotic nuclei will enable nuclear physicists to better understand the physics of exotic nuclei, their fundamental interactions, and develop applications for space exploration. Important criteria for neutron detectors include a high detection efficiency, the ability to provide neutron energy information, a fast response, efficient discrimination between neutrons and the gamma-ray background, and low cost. Discrimination between neutrons and gamma-rays is typically achieved with liquid scintillators. Unfortunately, liquid scintillators are rather bulky and hazardous to work with due to their low flash points, toxicity, and are difficult to transport. On the other hand, plastic scintillators such as those used in the Low Energy Neutron Detector Array (LENDA) at NSCL, and the Versatile Array of Neutron Detectors at Low Energy (VANDLE) at HRIBF offer efficient neutron detection but lack neutron/gamma pulse shape discrimination (PSD). Also the low light yield, and therefore the energy threshold at which these plastic scintillation detectors can operate, leaves much to be desired. A novel concept being developed at Radiation Monitoring Devices, Inc. and Sandia National Laboratory are tin-loaded Organic Glass Scintillators (OGS) which have gamma-ray spectroscopy capabilities as well as light yields and neutron/gamma PSD that are comparable to single crystalline scintillators such as trans-stilbene but can be fabricated in large sizes via a melt-casting process that is comparable to plastic scintillators. Thus, the goal of the proposed effort is to undertake a systematic investigation of these novel organic glass scintillators to advance the solid- state neutron detection technology with PSD capability. In the Phase I project, we plan to optimize novel OGS for nuclear physics experiments by undertaking two key tasks: 1) Evaluate new OGS host compositions and Ir3+ compounds to achieve highest possible the light yield for the metal-loaded OGS, and 2) develop a melt-casting process for the scale-up of OGS to plates measuring 3” x 3”, while maintaining its scintillation properties. The potential applications for the proposed OGS include nuclear physics, nuclear non-proliferation-large portal monitors, high energy particle physics research, nuclear waste characterization, industrial non-destructive evaluation, biological and materials research, astronomy, and health physics.