PNNL

Abstract

We are developing a next-generation unattended sensor for detecting anomalous radiation sources. The system uses a scintillator material with dual sensitivity to gamma rays and neutrons, Cs2LiYCl6:Ce (CLYC), to reduce the size and complexity of the design. CLYC also offers a best-case energy resolution under 4% full width at half maximum at 662 keV, and allows for particle discrimination by pulse amplitude as well as pulse shape. The unattended sensor features sixteen one-inch CLYC detectors, each read out by a photomultiplier tube and custom readout electronics. A ?eld-programmable gate array implements a suite of ef?cient processing algorithms for anomaly detection and isotope identi?cation, and transmits alarm information to a base station via a wireless link. The system is designed to operate on battery power for several weeks. In this paper, we report the energy resolution, linearity, detection ef?ciency, and temperature stability of the ?rst CLYC detectors acquired for the project. Rather than characterizing the scintillator material under ideal conditions, we evaluate the detectors with the components selected for the unattended sensor, acknowledging the tradeoffs imposed by small size, limited power budget, and uncontrolled environmental conditions.