Abstract
This paper presents an ultra-low-level gamma spectrometer designed to achieve the lowest possible limit of detection and the optimal sensitivity for low-activity samples in environmental research applications. The spectrometer is composed of high-purity germanium and is shielded by a combination of four layers of low-activity materials. The passive shield is surrounded by five plastic-scintillator-based veto detectors to employ the anticoincidence technique. Laboratory tests demonstrate that the background count rate in the range of 40-2,700 keV is 50(20) x 10(-3) cps kg(-1) Ge. The concept and performance of the system were also investigated using a Monte Carlo simulation method.