Development of a Si-PM-based GGAG radiation-imaging detector with pulse-shape discrimination capability to separate different types of radiation

We previously developed a radiation detector using a ceramic scintillator made for X-ray computed tomography (CT), Gd₃(GaAl)₅O₁₂:Ce (GGAG), combined with a position-sensitive photomultiplier tube (PSPMT) for the imaging of radiation. However, GGAG's scintillation wavelength is more suitable for silicon-based photodetectors than PSPMT, and so better performance is expected by combining it with a silicon-based photodetector. Therefore, here we combined a GGAG plate with silicon photomultiplier (Si-PM) arrays to develop a radiation-imaging detector. Our proposed Si-PM-based GGAG radiation-imaging detector consists of a 0.5-mm-thick GGAG plate, a light guide, and an 8 x 8 Si-PM array. The spatial resolutions of this imaging detector surpassed 0.31-mm FWHM for 5.5-MeV alpha particles. The spatial resolution of the Sr-Y-90 beta particles (maximum energy: 2.28 MeV) was ∼0.8 mm FWHM and 0.6-mm FWHM for Ca-45 (maximum energy: 0.24 MeV). The spatial resolutions for Co-57 (122 keV), Am-241 gamma photons (60 keV), and Cs-137 X-rays (∼35 keV) were 0.6-, 0.8-, and 1.0-mm FWHM, respectively. Since GGAG's scintillation decay curves for alpha particles are different from gamma photons or beta particles, we can use pulse-shape discrimination to separate the Am-241 alpha particles from the Cs-137 gamma photons as well as from the Sr-Y-90 beta particles.