A phoswich for thermal-neutron and gamma-ray detection

The challenge of simultaneous measurement of neutrons and gamma rays with good resolution has potential impact on numerous applications in, for example, national security. Here, we employ a phosphor-sandwich style detector, combining Gadolinium-Aluminium-Gallium-Garnet (GAGG(Ce)) and Cerium-Bromide (CeBr3) scintillators with a silicon photomultiplier for photodetection. Through pulse-shape discrimination (PSD), we are able to distinguish thermal neutron capture on the gadolinium from 7-ray detection in the CeBr3 with figure-of-merit in the region-of-interest of 1.406(5). In agreement with previous work we demonstrate that an improved signal-to-background can be achieved through the use of very thin GAGG(Ce) crystals, while also demonstrating the importance of the detector geometry in reducing the low-energy background.