Novel garnet ceramic scintillators for radioisotope identification

Preventing the proliferation of nuclear materials is critical in maintaining national security and safety. One key method is to identify Special Nuclear Materials, such as weapon-grade plutonium and highly enriched uranium, through their characteristic gamma-ray emissions. The key requirements for gamma-ray detectors used in such Radioactive Isotope Identifier Devices, include high energy resolution, high detection efficiency and low cost. The two most common gamma-ray detectors used in Radioactive Isotope Identifier Devices at present are NaI:Tl and LaBr3:Ce. These two scintillators provide a trade-off between energy resolution and cost. Since neither of these candidates is ideal, the quest for better scintillators continues, seeking to achieve the desired high performance without compromising on cost. To address this need for improved scintillators, we propose to investigate ceramic garnet scintillators for nuclear security application. Oxides with garnet structure are very promising host materials for scintillators with a number of compositions that show very good properties: high density (>6 g/cm3), high light yield (>40,000 ph/MeV), and fast decay times (<200 ns for the major component). Good proportionality and high energy resolution are also achievable with the garnet scintillators. In Phase-I, we will implement ceramic processing of selected garnet compositions and optimize activator and co-activators concentrations to achieve optimal scintillation properties. We will also explore Li and B based garnet compositions for neutron detection as well as dual mode capabilities for these class of materials. In addition to instrumentation used in nuclear non-proliferation monitoring, the new ceramic garnet scintillators will find applications in physics research, radiography systems used for homeland security (e.g. high energy, high speed radiography), and in medical systems such as positron emission tomography and X-ray computed tomography.