High Quantum Efficiency, Fast Detectors for the Readout of Scintillators for Gamma-Ray Detection

Gamma-ray spectrometers consisting of inorganic scintillators coupled to optical detectors such as photomultiplier tubes (PMTs) are an important element of the systems that are used to monitor and prevent the spread of special nuclear materials. Two very important requirements for the scintillation detectors used as gamma-ray spectrometers in homeland security monitoring include high sensitivity and high energy resolution. New, bright scintillators such as cerium doped lanthanum bromide (LaBr3:Ce) exhibit very energy resolution. The energy resolution of LaBr3:Ce with PMT readout is at present limited by photoelectron statistics. The quantum efficiency of even the best PMTs over the emission spectrum of LaBr3:Ce (340-450 nm region) is quite low (about 20-30%). As a result, the low PMT quantum efficiency is one of the main factors that limits the energy resolution of LaBr3:Ce scintillators at present. As a result, the goal of the proposed project is to design, build and evaluate advanced, silicon based photodetectors that have very high quantum efficiency for scintillator readout and are also fast and compact.