Investigating the time resolution of a compact multidimensional gamma-spectrometer

Abstract

Multidimensional gamma-spectrometry is a powerful technique for making low-level nuclear measurements. The systems typically utilise multiple sodium iodide detectors to measure coincident or anti-coincident gamma-energies. This allows significant background reduction and high selectivity of cascading radionuclides including 22Na. As events are rejected or selected based on their event time, the timing resolution of the multi-channel analyser (MCA) is important. This has been assessed for three compact MCA systems produced by Canberra and Ortec. The Canberra OspreyTM and LynxTM provided the best timing performance, capturing 88.3 and 97.9% of 22Na positron emissions within 200 ns. In comparison only 12.5% of events were measured within 200 ns by the Ortec digiBASE-ETM. However all systems captured the majority of events within 1000 ns, providing multidimensional spectra that allow the evaluation of simultaneous energy combinations.