EFFECT/BACKGROUND CORRELATIONS IN NANOSECOND NEUTRON ANALYSIS

Abstract

Nanosecond Neutron Analysis (NNA) technology is used for detection, identification, and localization of explosives. The main source of background in NNA are gamma-rays induced by fast tagged neutrons in non-explosives materials, and gamma-rays produced by non-tagged neutrons slowed down or emitted at the large angles to the trajectories of tagged neutrons. The results of experimentations and numerical simulation of NNA carried out in Russian Research Center “Kurchatov Institute” are reported. This work has been implemented for the geometry of experimental setup for explosives detection. The energy and time dependencies of the detected gamma-rays were obtained due to the selection of events by NNA technology. The comparison of theoretical and experimental data is considered, and the ways of improvement of their convergence are discussed. The basic components of background induced by neutron interaction with various objects (neutron generator units, shielding, gamma-detector) as well as sources of time fluctuations affecting the total time resolution are examined. The experimental and theoretical results show that the NNA technology provides effective (by 2–4 orders of magnitude) suppression of background by spatial and time discrimination of events.