Neutron Source Localization Using Plate-Shaped Fast Neutron Detectors

Abstract

To ensure nuclear security at major public events, portable detectors are essential for surveying wide areas and verifying the absence of nuclear and radioactive materials. Fast neutron detectors enable surveys for localizing neutron-emitting sources and nuclear materials over wide areas. A neutron detector with pulse-shape-discrimination plastic scintillators sensitive to fast neutrons is used herein, thereby suppressing responses to scattered neutrons and reducing gamma-ray background. By adopting a plate-shaped scintillator, the detector exhibits high characteristic directionality. From the measured count-rate distribution along the survey path, both the source distance and point of closest approach can be inferred from peaks and widths of the distribution. However, for more rapid and reliable neutron source localization, empirical functions capable of reproducing the measured count-rate distribution are highly desirable. This paper proposes simple empirical functions and demonstrates that reliable source positions can be determined through chi-squared fitting.