Fast, Dense, Non-Hygroscopic Scintillators for Particle Detectors

Problem Statement Nuclear and high energy physics research has a need for new, high-performance particle scintillation detectors with better energy resolutions, higher light yields (>10,000 photons/MeV), high densities, fast decay times, and are radiation hard. Along with these desirable properties, these materials must also be stable, low cost, and easy to produce in massive quantities. Recently advances in materials study for radiation sensors, particularly the latest discovery of high-density thallium-based inorganic scintillation crystals, is spurred by a necessity to improve isotope identification capability, for example, for homeland security applications. These new materials also possess many of the required properties for detection materials in high energy physics applications and research. Continuous search for improved scintillation materials for better radiation detection is important, since an ideal scintillator for such applications has yet to be discovered. Moreover, advances in high energy physics depend on the advancement in materials research. Phase I Objective XI, Inc. will investigate and study non-hygroscopic Tl-based scintillation compounds. To increase density and improve on the scintillation performance, we will replace alkali ions with isovalent heavy ion such as Tl-ion, which has a high Z number. Substitution with a high Z constituent has been shown to significantly increase material density. The goal of this project will be to develop non-hygroscopic scintillators with high densities (>5 g/cm3), high light yields (>20,000 photons/MeV), with a fast decay time component (<40 ns) and sufficiently radiation hard. Phase I Plan We will focus on investigation and growth of new scintillators (undoped and doped) with high densities by adding or replacing alkali ions with isovalent heavy ion such as Tl-ion, which will increase both density and Zeff, improving the materials’ stopping power that is favorable for gamma-ray detectors. Other favorable properties will be good energy resolution and high light yield. After growth is completed, samples from the boule will be prepared for thermal and optical characterization, including spectroscopy (emission and excitation spectra) as well as for scintillator measurements such as pulse height spectrum, decay time, and nonproportionality. Radiation damage study on these new scintillators will also be conducted. Commercial Applications and Other Benefits Scintillators produced in this project will enhance cost effectiveness at the instrument level, based on low projected cost of the proposed compounds as much thinner or smaller crystal sizes can be deployed to achieve the same efficiency as currently used detectors. These new scintillators will be beneficial to the high energy physics community and can also improve detection capability in homeland security applications, like incorporation into radioisotope identification devices (RIID’s), as well as devices used in medical physics.