Project of the Underwater System for Chemical Threat Detection

Abstract

In this article we describe a novel method for the detection of explosives and other hazardous substances in the marine environment using neutron activation. Unlike the other considered methods based on this technique we propose to use guides for neutron and gamma quanta which speeds up and simplies identication. Moreover, it may provide a determination of the density distribution of a dangerous substance. First preliminary results of Monte Carlo simulations dedicated for design of a device exploiting this method are also presented.

Monte Carlo N-Particle simulations of an underwater chemical threats detection system using neutron activation analysis

“…However, the recoil α particle registration would not only reduce further the background, but may also give opportunity to obtain tomographic-like image of the inspected object. Knowing position of the α particle interaction in the generator and the location of the γ-rays hit in the detector one can use the time difference between these two measurements to determine the point of emission of the γ quantum (detailed explanation of this idea can be found in [14]). Simulations show that the elemental ratios for materials which can be likely found on the bottom of the Baltic Sea are much different from the one for mustard gas (e.g.…”

Design of the SABAT System for Underwater Detection of Dangerous Substances

“…This shows clearly that all the faces of the detector not connected to the guide should be covered with thick layer of material absorbing γ quanta and neutrons which constitute another big source of background. This noise can be also significantly reduced by the requirement of the coincident detection of the α particle generated together with neutron, which allows for the neutron tagging [11]. As one of the possible way of the background suppression via time-of-flight method we consider an application of plastic scintillators in order to take advantage of their excellent timing properties, as recently demonstrated in case of low energy gamma quanta [16,17,18,19].…”

“…In order to optimize the dimensions and relative positions of detectors and guides we have developed dedicated open source software package written in the C++ programming language [11]. This simulation tool is using novel methods of geometry definition and particle tracking and the Open MPI library supporting parallel computing [13].…”

“…This can be done requiring of the coincident detection of the α particle generated together with neutron or by covering all the detector faces not connected to the gamma quanta guide with thick layer of absorber. Identification of sulfur and chlorine is difficult due to neutron capture on hydrogen giving lines of very close energy and chlorine content in the sea water [11]. However, using the gamma quanta guide one can detect γ rays from these two elements not affected by scattering in the water which gives a great advantage in the identification.…”

“…The detector is then counting the gamma quanta from thermal neutron capture and secondary neutrons originating from the irradiated object. The identification is done by searching for anomalies in the observed spectra of gamma quanta and neutrons [11]. However, these methods do not allow to detect explosives buried deeper in the bottom of the sea and strong attenuation of neutrons and gamma quanta significantly increases the exposure time.…”