Enhanced information extraction in the multi-energy x-ray tomography for security

Thesis (Ph.D.)--Boston UniversityX-ray Computed Tomography (CT) is an effective nondestructive technology widely used for medical diagnosis and security. In CT, three-dimensional images of the interior of an object are generated based on its X-ray attenuation. Conventional CT is performed with a single energy spectrum and materials can only be differentiated based on an averaged measure of the attenuation. Multi-Energy CT (MECT) methods have been developed to provide more information about the chemical composition of the scanned material using multiple energy-selective measurements of the attenuation. Existing literature on MECT is mostly focused on differentiation between body tissues and other medical applications. The problems in security are more challenging due to the larger range of materials and threats which may be found. Objects may appear in high clutter and in different forms of concealment. Thus, the information extracted by the medical domain methods may not be optimal for detection of explosives and improved performance is desired. In this dissertation, learning and adaptive model-based methods are developed to address the challenges of multi-energy material discrimination for security. First, the fundamental information contained in the X-ray attenuation versus energy curves of materials is studied. For this purpose, a database of these curves for a set of explosive and non-explosive compounds was created. The dimensionality and span of the curves is estimated and their space is shown to be larger than two-dimensional, contrary to what is typically assumed. In addition, optimized feature selection methods are developed and applied to the curves and it is demonstrated that detection performance may be improved by using more than two features and when using features different than the standard photoelectric and Compton coefficients. Second, several MECT reconstruction methods are studied and compared. This includes a new structure-preserving inversion technique which can mitigate metal artifacts and provide precise object localization in the estimated parameter images. Finally, a learning-based MECT framework for joint material classification and segmentation is developed, which can produce accurate material labels in the presence of metal and clutter. The methods are tested on simulated and real multi-energy data and it is shown that they outperform previously published MECT techniques

Mid-Infrared Laser Spectroscopy Applications in Process Analytical Technology: Cleaning Validation, Microorganisms, and Active Pharmaceutical Ingredients in Formulations

Mid-infrared (MIR) lasers are very high-brightness energy sources that are replacing conventional thermal sources (globars) in many infrared spectroscopy (IRS) techniques. Although not all laser properties have been exploited in depth, properties such as collimation, polarization, high brightness, and very high resolution have contributed to recast IRS tools. Applications of MIR laser spectroscopy to process analytical technology (PAT) are numerous and important. As an example, a compact grazing angle probe mount has allowed coupling to a MIR quantum cascade laser (QCL), enabling reflectance-absorbance infrared spectroscopy (RAIRS) measurements. This methodology, coupled to powerful multivariable analysis (MVA) routines of chemometrics and fast Fourier transform (FFT) preprocessing of the data resulted in very low limits of detection of active pharmaceutical ingredients (APIs) and high explosives (HEs) reaching trace levels. This methodology can be used to measure concentrations of surface contaminants for validation of cleanliness of pharmaceutical and biotechnology processing batch reactors and other manufacturing vessels. Another application discussed concerns the enhanced detection of microorganisms that can be encountered in pharmaceutical and biotechnology plants as contaminants and that could also be used as weapons of mass destruction in biological warfare. In the last application discussed, the concentration of APIs in formulations was determined by MIR laser spectroscopy and was cross validated with high-performance liquid chromatography

CATIONIC LATEX NANOPARTICLES IN ELECTROKINETIC CHROMATOGRAPHY: SYNTHESIS, CHARACTERIZATION, AND APPLICATION TO THE SEPARATION OF EXPLOSIVES

Electrokinetic chromatography (EKC) is a powerful analytical technique that uses the instrumentation of capillary electrophoresis (CE) and the principles of chromatography to separate ionic and neutral analytes. A capillary is filled with background electrolyte (BGE), and when a voltage is applied ionic species migrate to the electrodes. Neutral compounds have no mobility, so a pseudo-stationary phase (PSP) is added to the BGE that consists of an ionic group to provide mobility and a hydrophobic group to interact with analytes. Analytes interact with the PSP which changes their apparent mobilities, leading to a separation. It is possible to coat the negatively charged silica surface of a capillary with a cationic polymer, reverse the polarity of the electrodes, and use a cationic PSP to perform separations. This is the subject of this dissertation. RAFT polymerization was used to create diblock copolymers that self-assemble into latex nanoparticles and used as PSPs for EKC. Two cationic monomers, [2-(Acryloyloxyl)ethyl]trimethyl-ammonium chloride (AETMAC) and (3-Acrylamidopropyl)trimethylammonium chloride (APTAC), and three hydrophobic monomers, butyl acrylate (BA), ethyl acrylate (EA), and methyl acrylate (MA) were investigated. RAFT polymerization was an effective way to create the desired materials, and several techniques were used for characterization. Unexpected band broadening was observed when the nanoparticles were used as PSPs, so an additional cationic homopolymer, PAETMAC, was needed to coat the capillaries to prevent hydrophobic interactions at the capillary surface. The linear solvation energy relationships (LSER) model was used to compare different cationic latex nanoparticles. The choice of cationic block did not affect selectivity, but nanoparticles with MA cores showed a significant difference from nanoparticles with EA or BA cores. Finally, PAETMAC coated capillaries and cationic latex nanoparticles were used to separate anions and nitro compounds found in explosives residues. Separations can be performed in less than 10 minutes. The hydrophobic anions perchlorate and thiocyanate are retained by the nanoparticles, and acetonitrile was added to the BGE to reduce band broadening of these analytes. Future directions for this work include further characterization of the diblock copolymers, further optimization of the explosives separation, and the development of a portable fluorescence quenching detection system

Ionization signals from electrons and alpha-particles in mixtures of liquid Argon and Nitrogen - perspectives on protons for Gamma Resonant Nuclear Absorption applications

In this paper we report on a detailed study of ionization signals produced by Compton electrons and alpha-particles in a Time Projection Chamber (TPC) flled with different mixtures of liquid Argon and Nitrogen. The measurements were carried out with Nitrogen concentrations up to 15% and a drift electric feld in the range 0-50 kV/cm. A prediction for proton ionization signals is made by means of interpolation. This study has been conducted in view of the possible use of liquid Ar-N2 TPCs for the detection of gamma-rays in the resonant band of the Nitrogen absorption spectrum, a promising technology for security and medical applications

Commercial Systems for the Direct Detection of Explosives (for Explosive Ordnance Disposal Tasks)

The main goal of this study, carried out by the author on behalf of the Swiss Defence Procurement Agency (DPA), was to characterise existing technologies, and identify corresponding commercially available systems, for the direct detection of explosives for Explosive Ordnance Disposal (EOD) tasks. Systems should be able to determine if a given piece of munition contains explosives or is inert, and ideally in the former case to establish the type of explosive (see also Annex A2.1). This will be often referred to in the following as the “task at hand”, or the “task of interest to us”. Note that the object in questions has already been detected by other means (usually visually, e.g. lying on the surface) – what is needed is the capacity to characterise its contents (explosive or inert)

Detection of organic materials by spectrometric radiography method

In this paper we report a spectrometric approach to dual-energy digital radiography that has been developed and applied to identify specific organic substances and discern small differences in their effective atomic number. An experimental setup has been designed, and a theoretical description proposed based on the experimental results obtained. The proposed method is based on application of special reference samples made of materials with different effective atomic number and thickness, parameters known to affect X-ray attenuation in the low-energy range. The results obtained can be used in the development of a new generation of multi-energy customs or medical X-ray scanners.Comment: 6 pages, 2 tables, 5 figures, will be presented at the Workshop on X-Ray Imaging, 22-24 October, 2008, Dresden, German

SIMULATION OF NEUTRON INSPECTION TECHNIQUES BASED ON LASER-PLASMA NEUTRON BEAM AND FIRST EXPERIMENTS WITH CF SOURCE

openThis thesis is devoted to laser-plasma acceleration technology with an aim to produce the neutron source to foresee the use of neutron beams for addressing volumetric inspection of cargo container in order to provide the feasibility for custom border inspection on seaports and airports. We tried to significantly improve the system for simultaneous detection of hazardous and illicit materials. Neutron beams interact with the samples under study, inducing the emission of characteristic gamma radiation. The analysis of the emitted radiation allows retrieving the composition of a large variety of materials, avoiding visible damage or changes in the chemical composition. Many of these techniques have relied on massive and expensive radiation sources (e.g. particle accelerators) for several decades. In the last years, the advent of a new generation of ultra-short and super-intense lasers of higher intensities of 10 19 W/cm 2 paved the way for the exploration of new laser plasma interaction scenarios. Among the others, laser-driven particle acceleration, consisting in the production of high-energy electrons and ions. When a laser pulse is focused on a solid target, is attracting increasing attention in the scientific community. Indeed, the compact size and multi-particle nature of laser-based accelerators make them attractive for applications in several fields, from astrophysics to medical science. However, the applicability of laser-driven radiation sources to the elemental analysis of materials remains substantially unexplored. Therefore, the goal of this thesis work is to address the possibility of neutron productions by exploiting laser-driven particle acceleration mechanism for materials characterization, using neutron-in and gamma-out reactions. To this aim, we provide the brief detail for neutrons production in laser plasma acceleration using fusion and portable laser driven acceleration in target normal sheath acceleration (TNSA) mechanism using d(d,n)He, 7Li(p,n)4Be, 3Li(d,n)4Be reactions. Neutrons produced from these nuclear reactions are used in order to characterize the target object for materials identification. Geant4 simulation was made in an experimental approach. First, to make laser-driven neutron sources suitable for the mentioned applications. Then neutrons produced were used to characterize the numerous illicit and explosives materials that can be mixed and diluted to create countless varieties, the majority of which are made up entirely of the components H, C, N, and O. Lastly, the simulation was performed with an radioactive neutron source and results were obtained to test on basis of a proof-of-principle experiment in laboratory. The outcomes of this study confirms that materials characterization can be performed with the neutron produced from laser facilities. The predictions made from 252 Cf neutron source shows that 252 Cf source emits high-energy correlated neutrons and gammas, making it a valuable interrogation source. Major problem of this source is, it cannot be turned off, and emits radiation continually. This limits their use to small experiments that depends on constant neutron flux without pulsed emission. Therefore, it may be advantageous to switch on and off the interrogating source, laser driven fusion neutron sources are practically suitable since they lack intrinsic gamma-neutron correlations.This thesis is devoted to laser-plasma acceleration technology with an aim to produce the neutron source to foresee the use of neutron beams for addressing volumetric inspection of cargo container in order to provide the feasibility for custom border inspection on seaports and airports. We tried to significantly improve the system for simultaneous detection of hazardous and illicit materials. Neutron beams interact with the samples under study, inducing the emission of characteristic gamma radiation. The analysis of the emitted radiation allows retrieving the composition of a large variety of materials, avoiding visible damage or changes in the chemical composition. Many of these techniques have relied on massive and expensive radiation sources (e.g. particle accelerators) for several decades. In the last years, the advent of a new generation of ultra-short and super-intense lasers of higher intensities of 10 19 W/cm 2 paved the way for the exploration of new laser plasma interaction scenarios. Among the others, laser-driven particle acceleration, consisting in the production of high-energy electrons and ions. When a laser pulse is focused on a solid target, is attracting increasing attention in the scientific community. Indeed, the compact size and multi-particle nature of laser-based accelerators make them attractive for applications in several fields, from astrophysics to medical science. However, the applicability of laser-driven radiation sources to the elemental analysis of materials remains substantially unexplored. Therefore, the goal of this thesis work is to address the possibility of neutron productions by exploiting laser-driven particle acceleration mechanism for materials characterization, using neutron-in and gamma-out reactions. To this aim, we provide the brief detail for neutrons production in laser plasma acceleration using fusion and portable laser driven acceleration in target normal sheath acceleration (TNSA) mechanism using d(d,n)He, 7Li(p,n)4Be, 3Li(d,n)4Be reactions. Neutrons produced from these nuclear reactions are used in order to characterize the target object for materials identification. Geant4 simulation was made in an experimental approach. First, to make laser-driven neutron sources suitable for the mentioned applications. Then neutrons produced were used to characterize the numerous illicit and explosives materials that can be mixed and diluted to create countless varieties, the majority of which are made up entirely of the components H, C, N, and O. Lastly, the simulation was performed with an radioactive neutron source and results were obtained to test on basis of a proof-of-principle experiment in laboratory. The outcomes of this study confirms that materials characterization can be performed with the neutron produced from laser facilities. The predictions made from 252 Cf neutron source shows that 252 Cf source emits high-energy correlated neutrons and gammas, making it a valuable interrogation source. Major problem of this source is, it cannot be turned off, and emits radiation continually. This limits their use to small experiments that depends on constant neutron flux without pulsed emission. Therefore, it may be advantageous to switch on and off the interrogating source, laser driven fusion neutron sources are practically suitable since they lack intrinsic gamma-neutron correlations

Phenomenological Model for Infrared Emissions from High-Explosive Detonation Fireballs

Time-resolved infrared spectra were recently collected via a Fourier-transform spectrometer (FTS) from the detonation fireballs of two types of conventional military munitions (CMM) as well as uncased TNT and four types of enhanced novel explosives (ENEs). The CMM spectra are dominated by continuum emission, and a single-temperature Planckian distribution, modified for atmospheric attenuation, captures most of the variation in the data. Some evidence of selective emission is identified by systematic patterns in the fit residuals. The behavior of these systematic residuals affords a distinction between the two types of CMMs studied. The uncased TNT and ENE spectra appear strongly influenced by both continuum and selective emission. A physics-based spectral model is developed consisting of seven parameters: size, temperature, particulate absorption coefficient, and gas concentrations for H2O, CO2, CO, and HCl. Fitting affords a high-fidelity representation with features that correlate with HE characteristics. The hydrogen-to-carbon ratio (R) separates the TNT and ENE events and is consistent with stoichiometric expectations. Average values of R are compared with stoichiometry (in parenthesis): TNT 1.13 (0.79); ENE0B 9.2 (21.3); ENE1 4.9 (6.7); ENE2A 4.6 (5.8); ENE2B 6.5 (6.7). Bayesian discrimination boundary between TNT and ENE is R = 1.67 and the mean probability of error is less than 0.3% for this two-class problem. The Fisher ratio is 17.4 and ENE can be distinguished from TNT with 99% detection rate with corresponding false-alarm rate of less than 10-4%

Reducing Material Attractiveness Utilizing Pu-238 and U-232

Decreasing the material attractiveness of uranium and plutonium materials is crucial to nuclear nonproliferation. The International Atomic Energy Agency (IAEA) implements safeguards across the world on a limited budget. Not only does decreasing material attractiveness reduce the possibility of proliferation, but also may lighten the financial burden on the IAEA if safeguards can be reduced. Two particular isotopes that have negative material attractiveness traits are 238Pu and 232U. Without isotopic separation technology, these isotopes cannot be removed from plutonium and uranium materials respectively. Both 238Pu and 232U produce large quantities of heat by alpha decay. High decay heat is considered one of the primary impacts on material attractiveness. This decay heat causes major issues during weaponization and can render the high explosives in a weapon useless and cause failure in the materials if high enough temperatures are reached. In addition to high alpha decay heat, 238Pu has a high spontaneous fission neutron generation rate, which can lead to a reduction in the yield of a nuclear weapon. 232U’s daughter products give a relatively high dose rate over time. Both the dose rate and heat generation increase over time, reaching a maximum after 10 years. 232U will also create difficulty during the enrichment process. Considering 232U is lighter than 235U, its concentration will increase at a higher rate during enrichment. The decay of 232U in gaseous UF6 can destroy UF6 molecules creating a variety of lighter molecules that must be separated from the enrichment stream. This study will evaluate the effects of 238Pu and 232U on material attractiveness. The material attractiveness of these materials will be quantified using multiple methods in an attempt to make a broad statement about their attractiveness. In order to better understand the feasibility of the introduction of 232U into a civilian nuclear fuel cycle, the effects on safety, security, and safeguards will also be explored