Pixelated dual module GYGAG directional gamma spectrometer

We report on a small gamma spectrometer with directional detection, based on two modules. Each module contains an array of 128 scintillator pixels coupled to reverse-biased photodiodes, an ASIC and a microcontroller. Modules communicate via USB and are operated via an Android GUI on a WiFi-connected device. Transparent ceramic GYGAG ((Gd,Y,Ce)3(Ga,Al)5O12) garnet scintillator pixels offer energy resolution as good as 3.1% at 662 keV for individual pixels. We previously reported on an eight-module planar spectrometer, based on the same technology1. The current compact system uses two modules in a back-to-back configuration to improve its speed and accuracy in locating a gamma-emitting source in a 4-pi field of view. This dual module system (~2.5 x 2.5 x 3.5 inches) is suitable as a pager-sized RIID or spectroscopic personal radiation detector (SPRD). Multiple dual module units can be combined for improved efficiency. Spectroscopic and directional performance will be described.