Anthony A. Faust

A Comparison of Fast Inorganic Scintillators for Thermal Neutron Analysis Landmine Detection

The Improved Landmine Detector System, a militarily fielded, teleoperated vehicle-mounted multi-sensor landmine detector, uses a thermal neutron analysis (TNA) detector to confirm the presence of a mine by detecting the bulk nitrogen in its explosives. To improve the nitrogen sensitivity or measurement times of the TNA detector, higher gamma ray rates will be required. The chief bottleneck to achieving the maximum possible performance from the present TNA or future versions is the relatively slow fluorescent decay time of the NaI(Tl) scintillators which are currently used. An experimental investigation was undertaken to compare a number of modern, fast inorganic scintillators to NaI(Tl) with respect to parameters relevant to TNA landmine detection, including efficiency, energy resolution, linearity, available size and cost. This paper presents results in the context of the high-rate, high-gamma-energy environments expected in such a TNA application. Large (7.62 cm times 7.62 cm) LaBr3:Ce scintillators, and to a lesser degree LaCl3:Ce, were found to stand-out as as the principal candidates for the detector upgrade to the TNA confirmation system. Their properties also make them ideal candidates for fast neutron analysis and associated particle imaging bulk explosives detectors.

Development of a Coded Aperture X-Ray Backscatter Imager for Explosive Device Detection

Defence R&D Canada has an active research and development program on detection of explosive devices using nuclear methods. One system under development is a coded aperture-based X-ray backscatter imaging detector designed to provide sufficient speed, contrast and spatial resolution to detect antipersonnel landmines and improvised explosive devices. The successful development of a hand-held imaging detector requires, among other things, a light-weight, ruggedized detector with low power requirements, supplying high spatial resolution. The University of California, San Diego-designed HEXIS detector provides a modern, large area, high-temperature CZT imaging surface, robustly packaged in a light-weight housing with sound mechanical properties. Based on the potential for the HEXIS detector to be incorporated as the detection element of a hand-held imaging detector, the authors initiated a collaborative effort to demonstrate the capability of a coded aperture-based X-ray backscatter imaging detector. This paper will discuss the landmine and IED detection problem and review the coded aperture technique. Results from initial proof-of-principle experiments will then be reported.

Canadian teleoperated landmine detection systems. Part I: The improved landmine detection project

The system developed under the Improved Landmine Detector Project is a teleoperated, multi-sensor, vehicle-mounted mine detector for low metal content and non-metallic mines to meet the Canadian requirements for rear area mine clearance in combat situations and peace-keeping on roads and tracks. The system consists of a purpose-built teleoperated vehicle carrying a forward looking infrared imager, a 3 m wide, down-looking highly sensitive electro-magnetic induction detector and a 3 m wide down-looking ground probing radar, which all scan the ground in front of the vehicle. Scanning sensor information is combined using a suite of navigation sensors and custom designed navigation, spatial correspondence and data fusion algorithms. Suspicious targets are then confirmed by a thermal neutron analysis detector. Key to the success of the system is the combination of sensor information, which requires coordinated communication between the sensors and navigation system and well designed sensor co-registration, spatial correspondence and data fusion methodologies. The advanced development model was completed in October 1997. Results are presented from Canadian and independent US trials in summer 1998. Four production units, based on the prototype technology, were delivered to the Canadian Forces in 2002, making the system the first militarily fielded, teleoperated, multi-sensor vehicle-mounted mine detector.

The Feasibility of Neutron Moderation Imaging for Land Mine Detection

Neutron moderation land mine detection involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons which return. This technique has been studied since the 1950s, but only using non-imaging detectors. Without imaging, natural variations in moisture content, surface irregularities, and sensor height variations produce sufficient false alarms to render the method impractical in all but the driest conditions. This paper describes research to design and build a prototype land mine detector based on neutron moderation imaging. After reviewing various neutron detector technologies, a design concept was developed. It consists of a novel thermal neutron imaging system, a unique neutron source to uniformly irradiate the underlying ground, and hardware and software for image generation and enhancement. A proof-of-principle imager has been built, but with a point source offset from the detector to roughly approximate a very weak uniform source at the detector plane. Imagery from the detector of mine surrogates is presented. Realistic Monte Carlo simulations were performed using the same two dimensional neutron imaging geometry as the detector in order to assess its performance. The target-to-background contrast was calculated for various soil types and moisture contents, explosive types and sizes, burial depths, detector standoffs, and ground height variations. The simulations showed that the neutron moderation imager is feasible as a land mine detector in a slow scanning or confirmation role and that image quality should be sufficient to significantly improve detector performance and reduce false alarm rates compared to non-imaging albedo detection, particularly in moist soils, where surface irregularities exist and when the sensor height is uncertain. Performance capability, including spatial resolution and detection times, was estimated.

Canadian teleoperated landmine detection systems. Part II: Antipersonnel landmine detection

Continuing with the description of the Canadian teleoperated mine detection systems, in this paper we will focus on systems developed primarily for antipersonnel (AP) landmine detection. The Articulated Robotic Scanner (ARS) is a system approach that uses a generic robotic device capable of automatically moving a landmine detection sensor over natural ground surfaces in a manner similar to an operator. Exploiting the cost efficiency of proven high sensitivity commercial-off-the-shelf sensors, such as the metal detectors widely employed by military and humanitarian deminers, the high-precision automation of the ARS can be utilized to provide a low cost and low weight scanning imaging sensor that can be carried on a small autonomous platform. Concurrent with the ARS project, Defence R&D Canada – Suffield has maintained an active programme in the development of portable AP landmine detection systems, a number of which will be described. Together, these projects inspired a more ambitious vision, the Canadian Sensor Integration Concept (CANSIC), which applies the successful multi-sensor landmine detection approach to a small autonomous vehicle, using complementary sensors designed for antipersonnel landmine detection. Using a high-mobility robotic platform, the envisioned system incorporates five separate technologies: two hyper-spectral cameras, thermal and visual/near infrared, along with a scanning sensor imaging system mounted on a purpose build articulated robotic scanner, working in conjunction with a nuclear imaging confirmation sensor. Designed to provide clearance options for areas off established roadways, the goal is not only to operate in all environments and conditions that a deminer is able to, but also to extend the demining capabilities of military commanders and humanitarian demining project managers to situations where there is a high probability of casualities.

Development of a coded-aperture backscatter imager using the UC San Diego HEXIS detector

Defence R&D Canada-Suffield and the University of California, San Diego, have recently begun a collaborative effort to develop a coded aperture based X-ray backscatter imaging detector that will provide sufficient speed, contrast and spatial resolution to detect antipersonnel landmines and improvised explosive devices. While our final objective is to field a hand-held detector, we have currently constrained ourselves to a design that can be fielded on a small robotic platform. Coded aperture imaging has been used by the observational X-ray and gamma ray astronomy community for a number of years, which has driven advances in detector design that is now being realized in systems that are substantially faster, cheaper and lighter than those only a decade ago. With these advances, a coded aperture hand-held imaging system has only recently become a possibility. One group at the Center for Astrophysics and Space Sciences, University of California, San Diego, has had a longterm programme developing the CZT based HEXIS detector as the detection element of a coded aperture imager. Designed as a satellite payload, this low-power system is ruggedized and light-weight, all necessary qualities for incorporation into the envisioned portable imaging system. This paper will begin with an introduction to the landmine and improvised explosive device detection problem, followed by a discussion of the HEXIS detector. We will then present early results from our proof-of-principle experiments, and conclude with a discussion on future work.

Defence R&D Canada research on nuclear methods of landmine detection

Defence R&D Canada (DRDC) has an active research and development program on detection of landmines using nuclear methods. They are intended for confirmation by detection of characteristic radiation or imaging of back scattered intensity distributions. Both vehicle-mounted and person-portable systems are being developed. Research on thermal neutron analysis (TNA) was initiated in 1994 to provide a confirmation detector for the DRDC developed multisensor, teleoperated, vehicle-mounted, landmine detection system. A version is now commercially available and four units have been fielded by the Canadian Land Forces. A prototype next generation TNA, which uses an electronic neutron generator as a source, has been constructed. Preliminary tests have shown improved performance. Research is now ongoing to investigate the addition of a fast neutron analysis capability to the next generation TNA. Characterization studies and software improvements are being conducted. Related research is investigating whether fast inorganic scintillator materials can provide an improvement in energy resolution. For person-portable applications, both neutron and photon irradiation processes are being investigated. A prototype landmine detector based on neutron moderation imaging has been completed and preliminary images of antipersonnel mine simulants obtained. It consists of a novel thermal neutron imaging system, a unique neutron source to uniformly irradiate the underlying ground and hardware and software for image generation and enhancement. Simulations show that it should provide a significant improvement over non-imaging neutron backscatter systems. X-ray backscatter imaging research is concentrating on non-collimated approaches to enable it to be person-portable. One such method, coded aperture imaging, is being investigated and extensive simulations using Geant4 have demonstrated its merits. Initial joint experiments with UC San Diego, using their HEXIS detector, have been conducted.

Potential Discrimination of Toxic Industrial Chemical Effects on Poplar, Canola and Wheat, Detectable in Optical Wavelengths 400–2450 nm

This research examined the spectral response of poplar (Populus deltoides, Populus trichocarpa), wheat (Triticum aestivum), and canola (Brassica napus) leaves subjected to fumigation with gaseous phase toxic industrial chemical gases (TICs). The gases include ammonia (NH3), sulphur dioxide (SO2), hydrogen sulphide (H2S), chlorine (Cl2), and hydrogen cyanide (HCN). This study aimed to determine if: (1) vegetation subjected to TICs could be distinguished from background vegetation during varying growth stages and environmental stresses; and, (2) different TICs could be distinguished based on the spectral response of vegetation. The results showed that both environmental and TICs induced similar spectral features inherent to plants, which are related primarily to chlorophyll and water loss. These features include pigments in the visible and cellulose, lignin, lipids starches, and sugars in the SWIR. Although no specific spectral features could be tied to individual TICs an analysis of the data using vegetation indices showed that the TICs and environmental stresses result in diagnostic trends from healthy mature to highly stressed leaves. In addition combinations of specific indices could be used to distinguish the effects of NH3, SO2, Cl2 and their effect from that of other treatments of the study. The continued goal for this research program is to develop a remote detection capability for hazardous events such as a toxic gas leak. Our findings at the leaf level suggest that damage can be detected within 48 hrs and should last for an extended period. Thus, the next experimental step is to test if the results shown here at the leaf level can also be detected with airborne and satellites systems.

Observations on military exploitation of explosives detection technologies

Accurate and timely detection of explosives, energetic materials, and their associated compounds would provide valuable information to military commanders in a wide range of military operations: protection of fast moving convoys from mobile or static IED threats; more deliberate countermine and counter-IED operations during route or area clearance; and static roles such as hasty or deliberate checkpoints, critical infrastructure protection and support to public security. The detection of hidden explosive hazards is an extremely challenging problem, as evidenced by the fact that related research has been ongoing in many countries for at least seven decades and no general purpose solution has yet been found. Technologies investigated have spanned all major scientific fields, with emphasis on the physical sciences, life sciences, engineering, robotics, computer technology and mathematics. This paper will present a limited, operationally-focused overview of the current status of detection technologies. Emphasis will be on those technologies that directly detect the explosive hazard, as opposed to those that detect secondary properties of the threat, such as the casing, associated wires or electronics. Technologies that detect explosives include those based on nuclear radiation and terahertz radiation, as well as trace and biological detection techniques. Current research areas of the authors will be used to illustrate the practical applications.

Detection and dispersal of explosives by ants

The ability of animals to detect explosives is well documented. Mammalian systems, insects and even single celled organisms have all been studied and in a few cases employed to detect explosives. This paper will describe the potential ability of ants to detect, disperse and possibly neutralize bulk explosives. In spring 2008 a team of DRDC and Itres scientists conducted experiments on detecting surface-laid and buried landmines, improvised explosive devices (IEDs) and their components. Measurements were made using state-of-the-art short wave and thermal infrared hyperspectral imagers mounted on a personnel lift. During one of the early morning measurement sessions, a wispy, long linear trail was seen to emanate several meters from piles of explosives that were situated on the ground. Upon close visual inspection, it was observed that ants had found the piles of explosives and were carrying it to their ant hill, a distance of almost 20 meters from the piles. Initial analysis of the hyperspectral images clearly revealed the trail to the ant hill of explosives, despite being present in quantities not visible to the unaided eye. This paper details these observations and discusses them in the context of landmine and IED detection and neutralization. Possible reasons for such behaviour are presented. A number of questions regarding the behaviour, many pertinent to the use of ants in a counter-landmine/IED role, are presented and possible methods of answering them are discussed. Anecdotal evidence from deminers of detection and destruction of explosives by ants are presented.