Design and performance of a compact Cs2LiLaBr6(Ce) neutron/gamma detector using silicon photomultipliers

摘要

Cs2LiLaBr6(Ce) (CLLB) crystal scintillator shows great potential as a radiation detection material with excellent energy resolution for gammas, sensitivity to neutrons, and the ability to separate the two using pulse shape discrimination (PSD). Experiments have been performed testing this material using silicon photomultipliers for creation of compact, easily-portable detectors for dual gamma ray spectroscopy and neutron detection. Pulse shape discrimination in CLLB is achieved by analyzing the scintillation pulse decay on the time scales of >1 μs. This feature enables the silicon photomultipliers with low afterpulsing to achieve suitable discrimination. Experiments have been conducted attempting to find a suitable cost/efficiency compromise that maximizes performance by varying crystal cerium concentration along with silicon photomultiplier type and placement position. A disk of CLLB (diameter = 52 mm, thickness = 6 mm, 6Li enriched) coupled to a 6×6 mm2 silicon photomultiplier can achieve 4.4% gamma ray energy resolution at 1275 keV, and 74% thermal neutron detection efficiency with a high pulse shape discrimination figure-of-merit of 1.9.