When neutrons interact with nuclei, the resulting energy of the interaction can be released in the form of gamma rays, whose energy is characteristic of the nucleus involved in the reaction. The PELAN (Pulsed Elemental Analysis with Neutrons) system uses a pulsed neutron generator and an integral thermalizing shield that induce reactions that cover most of the entire neutron energy range. The neutron generator uses a d-T reaction, which releases fast 14 MeV neutrons responsible for providing information on chemical elements such as C, N, and O. During the time period between pulses, the fast neutrons undergo multiple elastic and inelastic interactions that lower their energy making them easier to be captured by chemical elements, such as H and Cl. The PELAN system has been used for a number of applications where non-intrusive, non-destructive interrogation is needed. This report illustrates examples of its performance in interrogations for unexploded ordnance (UXO), landmines, large vehicle bombs and illicit drug detection.
PELAN (the initials of Pulsed Elemental Analysis with Neutrons) is a device that has been developed to identify a landmine through the elemental constituents of its explosive. PELAN uses neutrons as the probing particles. The incident neutrons interact with the nuclei of the various chemical elements in the mine, emitting characteristic gamma rays that act as the fingerprints of the various chemical elements. PELAN is capable of identifying with the same probability of detection all types of high explosives (TNT, RDX etc.) either in plastic or metal encased landmines. Results of its evaluation with blind tests in Croatia and the US using anti-personnel and anti-tank landmines will be presented.
PELAN (Pulsed ELemental Analsys with Neutrons) is a man-portable system for the detection of explosives and chemical warfare agents, weighing 40 kg. It is based on the principle that explosives and other contraband contain various chemical elements such as H, C, N, O, etc. in quantities and ratios that differentiate them from ot her innocuous substances. The pulsed neutrons are produced with a pulsed 14 MeV (d-T) neutron generator. Separate gamma-ray spectra from fast neutron, thermal neutron and activation reactions are accumulated and analyzed to determine elemental content. Data analysis is performed in an automatic manner and a final result of whether a threat is present is returned to the operator. Since 1999, PELAN has undergone several field trials and demonstrations, including in 2001, demonstrations in Belgium andin the US of its ability to identify chemical warfare agents. We will review the results of these tests and also discuss the modifications made to the system.
KEYWORDS: Sensors, Explosives, Explosives detection, Data acquisition, Temperature metrology, Gamma radiation, Signal to noise ratio, Chemical analysis, Bismuth, Chemical elements
PELAN (Pulsed ELemental Analysis with Neutrons) is a portable system for the detection of explosives, weighing less than 45 kg. It is based on the principle that explosives and other contraband contain various chemical elements such as H, C, N, O, etc. in quantities and ratios that differentiate them from other innocuous substances. Neutrons are produced with a pulsed 14 MeV (d-T) neutron generator. Separate gamma-ray spectra from fast neutron, thermal neutron and activation reactions are accumulated and analyzed to determine elemental content. Data analysis is performed in an automatic manner and a final result of whether a threat is present is returned to the operator. Recently, a number of modifications were performed to improve PELAN. Since the bismuth germanate detector's light output changes with temperature, an automatic gain stabilization system has been designed. Also, the signal-to-noise ratio has been increased by the innovative use of a veto shield placed around the bismuth germanate detector. This shield reduces Compton-continuum as well as the background gamma rays. Results from tests of the gain stabilization and the veto shield will be shown.
KEYWORDS: Chemical elements, Land mines, Explosives, Sensors, Explosives detection, Silicon, Mining, Defense and security, Data acquisition, Chemical analysis
There has been much work increasing the sensitivity of detecting metallic objects in soils and other environments. This has lead to a problem in discriminating unexploded ordnance (UXO) and landmines form other metallic clutter. PELAN is a small portable system for the detection of explosives. PELAN weights less than 45 kg and is man portable. It is based on the principle that explosives and other contraband contain various chemical elements such as H, C, N, O, etc. in quantities and ratios that differentiate them from other innocuous substances. The pulsed neutrons are produced with a 14 MeV neutron generator. Separate gamma-ray spectra form fast neutron, thermal neutron and activation reactions are accumulated and analyzed to determine elemental content. The data analysis is performed in an automatic manner and a result of whether a threat is present is returned to the operator. PELAN has successfully undergone field demonstrations for explosive detection. In this paper, we will discuss the application of PELAN to the problem of differentiating threats from metallic clutter.
A neutron generator-based on-line coal analysis system has been developed, capable of measuring the major and minor chemical elements contained in coal. The system utilizes nuclear reactions produced from fast and thermal neutrons, as well as from neutron activation of isotopes with half- lives of seconds or minutes. Characteristic gamma rays detected with BGO (bismuth germanate) detectors are used for the identification of the various chemical elements. A key feature of the analyzer is its ability to analyze automatically three distinct gamma-ray spectra, and produce the elemental content of coal as it moves through a coal chute. A prototype analyzer has been built, able to analyze several tons/hour of coal. The main features of the analyzer are self-calibration independent of the coal seam, better accuracy in the determination of elements such as carbon, oxygen, and sodium, and diminished radiation risk.
Pulsed Fast/Thermal Neutron Analysis (PFTNA) is being employed in such diverse applications as: on-line coal analysis, detection of improvised explosive devices (IEDs), detection of contraband drugs, characterization of unexploded ordnance, and detection of landmines. In this work, the current research in the utilization of PFTNA in detection of drugs and IEDs will be discussed. Man-portable PFTNA systems have been built and currently are undergoing field trials. These systems can be inserted in confined spaces such as the boiler of a ship or into a tanker truck filled with liquid. The PFTNA system provides information on the major and minor chemical elements which compose the interrogated object. By measuring the elemental content or ratios of various elements, this system can differentiate between innocuous materials and materials such as drugs and IEDs. In laboratory trials, the PFTNA system can measure the carbon to oxygen ratio to an accuracy of 15% within a 5 minute time period. In all cases, hidden drugs and IEDs are identified through the measurement of the elemental content of the object, and the comparison of expected and measured elemental ratios.
The high penetrating powers of neutrons and of high energy gamma rays are utilized for the non-intrusive, non- destructive elemental characterization of materials. Neutrons produced in microsecond pulses interact with nuclei in the material, leading to the emission of gamma rays that have energies unique to each element. The pulsing of neutrons with a frequency of a few kHz allows the measurement of gamma rays resulting from a variety of neutron induced nuclear reactions. The elemental content of the material is deduced from the analysis of the gamma-ray spectra acquired during the neutron pulse and during the quiescent period between neutron pulses. A large number of elements from hydrogen to uranium can be identified and quantified within a few minutes of interrogation. This method called pulsed fast-thermal neutron analysis (PFTNA), can be used for on-line NDE, as well as for in situ characterization of materials. Devices based on PFTNA can be constructed in a stationary mode for on-line analysis, or in a transportable mode for in situ analysis. Examples on the utilization of the method include on-line coal analysis, on- line quality control in cement plans, measurement of oxidation of opaque metallic structures.
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