High-Precision Method for Revealing Hidden Substances by Means of Tagged Neutrons
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CLEI Experiment
High-Precision Method for Revealing Hidden Substances by Means of Tagged Neutrons A. M. Bakalyarov1)* and G. V. Muradian1) Received March 20, 2018
Abstract—A new method of employing A(n, n γ)A reactions of inelastic tagged-neutron scattering is proposed for revealing hidden substances. In contrast to the well-known method where substances are identified by measuring the spectrum of gamma rays, the new method consists in identifying substances by measuring the spectrum of neutrons. The neutron energy is measured by the time-of-flight method via detecting a (γ, n) pair and invoking the parameters of tagged neutrons. The detection of a neutron in a pair with a photon is also a factor that reduces the rate of accumulation of useful events. As is shown in the present study, however, the method in question possesses a number of important special features owing to which it boasts high precision and efficiency, as well as the ability of revealing a broad range of elements and hidden substances of small volume. A numerical simulation of both methods is performed. It is shown that the required time of measurements within the proposed method is one order of magnitude shorter, which makes it possible to circumvent that main difficulty encountered in applying the known method and associated with a low resource and a high cost of neutron sources. DOI: 10.1134/S1063778818050022
1. INTRODUCTION A high penetrating ability of fast neutrons and gamma rays; the dissimilarity of the spectra of gamma rays emitted by different nuclei in A(n, n γ)A inelastic-scattering reactions; and, finally, the creation of beams of tagged neutrons (neutrons of known energy and known direction and time of emission from a pointlike source) formed the basis for developing procedures for revealing explosive and other hazardous substances in various objects [1–13]. An object is exposed to tagged neutrons, whereupon gamma rays are detected, their detection time (tγ ) and the energy (Eγ ) deposited in the detector used being measured. By employing the value of tγ and the features of a tagged neutron, one determines the positions of nuclei A that emitted gamma rays. After that, one breaks down the object into cells by convention and, for each cell, calculates the spectrum S(Eγ ) of gamma rays recorded as those that were emitted from this cell. The elemental composition of each cell and the presence of hidden matter in it are determined on the basis of these spectra. A neutron tube serves as a source of tagged neutrons. The neutrons originate from the reaction T (d, n)4 He and have an energy of about 14 MeV. The neutron emission time, energy, and emission directions are 1)
National Research Center Kurchatov Institute, Moscow, 123182 Russia. * E-mail: [email protected]
established upon detecting the accompanying alpha particle. The method in question makes it possible to reveal substances usually containing carbon, nitrogen, and oxygen. Its advantage over the Xray scanning method consists in revealing hidden substances by the elemental compositio
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