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ASPECTS OF EXPLOSIVES DETECTION This page intentionally left blank ASPECTS OF EXPLOSIVES DETECTION Edited by MAURICE MARSHALL Defence Science and Technology Laboratory Fort Halstead, Sevenoaks Kent TN147BP United Kingdom JIMMIE C. OXLEY Chemistry Department University of Rhode Island USA Amsterdam • Boston • Heidelberg • London • New York • Oxford Paris • San Diego • San Francisco • Singapore • Sydney • Tokyo Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands Linacre House, Jordan Hill, Oxford OX2 8DP, UK First edition 2009 Copyright Ó 2009 Elsevier B.V. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-12-374533-0 For information on all Elsevier publications visit our web site at elsevierdirect.com Printed and bound in Great Britain 0809101112 10987654321 Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org CONTENTS Preface xi List of Contributors xiii 1 The Detection Problem 1 1 Explosive Detection Technology – The Impetus 1 2 The Problem 3 3 Detection Technologies 4 2 Explosives: The Threats and the Materials 11 1 Devices and Explosives 11 2 Fundamentals of Explosives 12 2.1 Usage of explosives 12 2.2 Detonation and deflagration 12 2.3 Primary and secondary explosives 12 2.4 Energy release, explosive output, and critical diameter 13 2.5 Chemistry of some common explosives 15 2.6 Military explosives 17 2.7 Plastic explosives 18 2.8 Commercial explosives 18 2.9 Propellants 19 2.10 Terrorist use of homemade explosives 20 2.11 Peroxide explosives 21 2.12 Exotic explosives 21 2.13 Energetic salts 22 2.14 Non-solid explosives 23 3 Implications for Detection 23 3 Detection of Explosives by Dogs 27 1 Introduction 27 2 The Scientific Basis of Explosives Detection by Dogs 28 2.1 What do dogs detect? 29 2.2 Sensitivity 31 2.3 Specificity 32 2.4 Dynamic range 34 2.5 Generalization 34 2.6 Duty cycle 35 2.7 Robustness 36 3 Training, Evaluation and Maintenance 37 4 Conclusions 38 v vi Contents 4 Colorimetric Detection of Explosives 41 1 Introduction 41 2 Nitroaromatic Explosives 43 3 Nitrate Esters and Nitramines 45 4 Improvised Explosives Not Containing Nitro Groups 49 5 Peroxide-Based Explosives 49 6 Urea Nitrate 52 7 Field Tests 53 5 Nuclear Technologies 59 1 Basis for Detection 59 2 Physics Underlying Nuclear Detection Methods 60 2.1 Detection principles 60 2.2 Neutron sources 65 2.3 Detectors 67 3 Survey of Neutron-Based Detection Approaches 72 3.1 Thermal neutron activation 72 3.2 Fast neutron activation 73 3.3 Fast neutron-associated particle 75 3.4 Pulsed fast neutron transmission spectroscopy 76 3.5 Pulsed fast neutron analysis 78 4 Survey of Non-Neutron-Based Nuclear Detection Methods 80 4.1 Nuclear resonance absorption 80 4.2 Nuclear quadrupole resonance 81 4.3 Nuclear resonance fluorescence 82 5 Problems with the Use of Nuclear Techniques for Explosive Detection 83 5.1 Field deployment of neutron sources 83 5.2 Health hazards because of radiation 83 5.3 Material activation 84 5.4 Neutron shielding 84 5.5 Public perception of radiation 84 6 Summary 84 6 X-ray Technologies 89 1 Introduction 89 2 X-ray Physics 90 2.1 Production of X-rays 90 2.2 Attenuation of X-rays 92 2.3 X-ray detectors 96 2.4 Dual-energy X-ray 97 2.5 Effective atomic number 100 3 History of X-Ray Screening Technology 102 3.1 Early history 103 3.2 Linear array X-ray scanners 104 Contents vii 3.3 Material discrimination 105 3.4 Automated detection 106 3.5 Other advancements in X-ray screening 109 3.6 Cargo scanners 110 4 X-Ray Inspection Systems 111 4.1 Conventional transmission 111 4.2 Dual-energy transmission systems 116 4.3 Multi-view systems 120 4.4 Scatter-based systems 121 4.5 Coherent X-ray scatter 123 5 Conclusion 127 7 CT Technologies 131 1 Introduction 131 2 Features of X-ray CT Imaging 131 3 Principles of CT Imaging 133 3.1 Single-slice CT 133 3.2 Multislice CT 137 3.3 Dual-energy CT 138 4 CT Scanner Operation 140 5 CT Scanner Design Considerations 144 8 Analysis and Detection of Explosives by Mass Spectrometry 147 1 Introduction 147 2 Trace Analysis of Explosives 150 2.1 Analysis of explosives by GC/MS 150 2.2 Analysis of explosives by LC/MS 151 3 Detection of Hidden Explosives 164 4 Conclusions 168 9 Advances in Ion Mobility Spectrometry of Explosives 171 1 Introduction 171 2 Sampling, Portals, and Inlets 172 3 Ion Formation and Ion Sources 178 3.1 Gas phase ionization reactions 178 3.2 Ion sources 181 4 Drift Tubes and Analyzer Development 186 5 Field Asymmetric IMS and Differential Mobility Spectrometry 188 6 Pre-Separation with IMS 192 7 Calibrations and Vapor Sources 194 8 Applications of IMS for Explosives Determinations 195 9 Future 198 viii Contents 10 Detection of Explosives Using Amplified Fluorescent Polymers 203 1 Introduction to Conjugated Polymers 203 2 Amplified Fluorescent Conjugated Polymers as Sensors 204 3 Electron Transfer Fluorescence Quenching 206 4 Polymer Design Principles for Solid-State Sensors 208 4.1 Thin-film conjugated polymer sensors and aggregation 208 4.2 Other important design parameters for sensitivity and selectivity – polymer 1 as a model 210 5 Ultra-trace TNT Detection with Operable Devices 213 6 Future Research Directions:Selected Examples 216 6.1 Future device improvements:chromatographic effects 216 6.2 Future material and transduction improvements – lasing sensors 218 7 Conclusion 220 11 Post-Blast Detection Issues 223 1 Objectives 223 2 Controlling the Aftermath 224 2.1 Questions from the media and government leaders 224 2.2 Scene control 224 2.3 Zoning 225 3 Initial Scene Examination 226 3.1 Map the scene 226 3.2 Was it a bomb? 226 3.3 The right question(s) 226 3.4 Damage assessment 227 3.5 Debris collection 228 3.6 Explosives residues 228 3.7 Aircraft 229 3.8 Quality assurance 230 3.9 Bomb scenes and mental stress 230 4 Laboratory Examinations 231 4.1 Work streams 231 4.2 Functions 231 4.3 Laboratory safety 231 4.4 Receipt 232 4.5 Receipt of items for trace analysis 232 4.6 Trace analysis 233 4.7 Storage and disposal 238 5 Facsimiles and Tests 238 6 Prediction of Explosive Effects 239 7 Summary 241 Contents ix 12 Explosives and Dangerous Chemicals: Constitutional Aspects of Search and Seizure 245 1 Introduction 246 2 The Fourth Amendment 246 2.1 Elements of Fourth Amendment 247 3 The Bill of Rights 251 4 The Fourteenth Amendment 251 5 The Law on Search and Seizure 251 5.1 Background: Fourth Amendment jurisprudence 251 5.2 Evidentiary search and seizure 252 5.3 Search and seizure exceptions 255 5.4 Remedies 261 6 Surveillance Technology 262 6.1 New surveillance technology 262 6.2 Tracking 263 6.3 Telephonic wiretap 263 6.4 Internet software 264 6.5 Data mining 264 7 Terrorism 265 7.1 Explosives 265 8 Technical Security Administration – Administrative Searches and Seizures 269 8.1 Transport security 269 8.2 Explosives detection 270 8.3 Passenger profiling 271 9 USA Patriot Act 272 9.1 Creation 272 9.2 Conflicts between Patriot Act and civil rights 274 9.3 Discussion 274 9.4 Application 275 10 Conclusion 275 Index 283 This page intentionally left blank PREFACE Detection and quantification of trace chemicals are a major thrust of analytical chemistry. In recent years, much effort has been put into developing detection systems for priority pollutants. Less mature are the detections of substances of interest to law enforcement and security personnel: narcotics, chemical agents, and explosives. This volume will discuss the detection of the latter, emphasizing explosive detection both because of its public importance and because it has undergone remarkable developments in the last decade. Terrorist events in the late twentieth century, for instance, airplanes blown out of the sky, such as PanAm 103 over Lockerbie and UTA 772 over Africa, and attacks on U.S. cities, for example, on the World Trade Center in New York in 1993 and the Murrah Federal Building in Oklahoma City in 1995, emphasized the danger of concealed explosives and led to calls for new technology to protect the public. However, because most explosives release little vapor, it was not possible to detect them by technology widely used on other organic substances.