Phillip C. Womble

Elemental online coal analysis using pulsed neutrons

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.

NELIS - a Neutron Inspection System for Detection of Illicit Drugs

NELIS (Neutron ELemental Inspection System) is currently being developed to inspect cargo pallets for illicit drugs. NELIS must be used in conjunction with an x‐ray imaging system to optimize the inspection capabilities at ports of entry. Pulsed fast‐thermal neutron analysis is utilized to measure the major and minor chemical elements in a non‐destructive and non‐intrusive manner. Fourteen‐MeV neutrons produced with a pulsed d‐T neutron generator are the interrogating particles. NELIS analyzes the characteristic gamma rays emitted from the object that are produced by nuclear reactions from fast and thermal neutrons. These gamma rays have different energies for each chemical element, and act as their fingerprints. Since the elemental composition of illicit drugs is quite different from that of innocuous materials, drugs hidden in pallets are identified through the comparison of expected and measured elemental composition and ratios. Results of tests of the system will be discussed.

On-line sulfur determination in coal with prompt gamma neutron activation

Abstract The prompt gamma neutron activation method has been found to be a useful technique for the on-line industrial measurements of bulk media. Based on this method, a system was developed for the on-line sulfur determination in coal. A 252Cf source is used for the production of neutrons and a high purity germanium (HPGe) detector is used for the detection of the gamma rays emitted. The system has been found to be linear over the range tested (0.5–6% in weight sulfur). Neutron-absorbing trace elements in coal such as Cl, were found to have no influence on the sulfur determination of the samples.

Results of field trials for the PELAN system

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.

Material Analysis Using Characteristic Gamma Rays Induced by Neutrons

Neutron interrogation based methods of non-destructive analysis are well established techniques employed in the field of bulk material analysis. These methods utilize a source of neutrons (a neutron probe) to irradiate objects under scrutiny. Nuclear reactions initiated by neutrons in the volume of the irradiated sample include the following: inelastic neutron scattering, thermal neutron capture, and neutron activation. As a result of nuclear reactions with the material inside the object, the “fingerprint” -rays are emitted with characteristic energies. These characteristic gamma rays are used for the elemental identification. By measuring and counting the number of -rays emitted with a specific energy, one can deduce the amount of the associated chemical element in the sample. The amounts of chemical elements measured allow specifying the chemical composition of the analyzed sample.

PELAN 2001: Current Status of the PELAN Explosives Detection System

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 detectors 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.

PELAN: a pulsed neutron portable probe for UXO and land mine identification

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.

Multielement analysis utilizing pulsed fast/thermal neutron analysis for contraband detection

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.

Evaluation of the Doppler‐Broadening of Gamma‐Ray Spectra from Neutron Inelastic Scattering on Light Nuclei

Neutron‐induced gamma‐ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma‐ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma‐ray peak is Doppler‐broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler‐broadening occurs primarily with gamma rays from neutron‐induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron‐induced gamma ray emitted from these nuclei will be Doppler‐broadened. We have f...

A Wireless Electronic Monitoring System for Securing Milk from Farm to Processor

The department of homeland security and the department of health and human services have targeted bulk food contamination as a focus for attention. Milk transport falls into three of the 17 targeted national infrastructure protection plan sectors including agriculture-food, public health and commercial facilities. The current manual methods of securing milk are paper intensive and prone to errors. The bulk milk transportation sector requires a security enhancement that will both reduce recording errors and enable normal transport activities to occur while providing security against unauthorized access. Our group has developed a milk transport security system which is an electromechanical access control and communication system that assures the secure transport of milk, milk samples, milk data, and security data between locations, and specifically between dairy farms, transfer stations, receiving stations, and milk plants. It includes a security monitoring system installed on the milk transport tank, a hand held device, optional printers, data server, and security evaluation software. The system operates automatically and requires minimal or no attention by the bulk milk hauler/sampler. The system is compatible with existing milk transport infrastructure, and has the support of the milk producers, milk transportation companies, milk marketing agencies, and dairy processors. The security protocol developed is applicable for transport of other bulk foods both nationally and internationally.