A Nal-Nal Coincidence Low Background Counting System for Low-level Gamma-ray Measurements

Abstract

A NaI-NaI coincidence low background counting system has been constructed to be used in radioenvironmental measurements. The slow timing technique, using the constant fraction timing single channel analyzer and coincidence unit, was used in the present system. The coincidence efficiencies of systems employing two and four NaI (Tl) detectors have been evaluated. A scintillation preamplifier with multiple inputs was constructed for summing the outputs of PM tubes. The performance of the system was tested using radioactive point sources and environmental samples. The detection efficiency of the NaI-NaI coincidence system employing four NaI (Tl) detectors was found to be high enough to measure low-level γ-ray activity of desired isotope in environmental samples with neither high background contribution nor interferences from other isotopes.