<title>Particle generators for the calibration and testing of narcotic and explosive vapor/particle detection systems</title>

Abstract

ABSTRACrA review of data on narcotics and explosives particulates is presented. Methods to generate particles of narcotics and explosives will be discussed with respect to resulting particle size distribution and mass output. The application of these standards to the testing of narcotic and explosive particle detection systems will be addressed 1 . INTRODUCTIONThere are a number of commercial instruments that claim to detect concealed contraband via the collection and analysis of particles of either the drug/explosive itself or a particle coated with the target molecule. The US Customs Service (USCS) and the United States Federal Aviation Administration (FAA) are in the process of testing these systems for their performance in the collection and detection of narcotic and explosive respectively. Standards are needed to perform these tests. One type of standard that has been proposed is a simulated rprit.2 This standard is ideal from an operational standpoint since it realistically duplicates the sample that the detection device will encounter in the "real world." The generation of fingerprints from explosives have been referred to being more of an art than a science1 due to the number of variables that as yet are not controlled. The variables include, age of explosives, type of surface the explosive is transferred to, size of finger, pressure applied to the explosive, and personal variations such as skin texture and oiliness. The FAA is currently involved in an international study to characterize the residue resulting from fingerprints deposited after someone handles explosives.3 The residue resulting from contact with C-4, P-4 and Semtex will be characterized with respect to total mass of RDX present and particle size distribution. The U. S. Customs service and Revenue Canada Customs and Excise are also involved in similar work with cocaine and heroin residues. Another type of standard proposed is one that can deposit particles on a surface as well as simulate the transport and migration of explosives/narcotics through space. Because most explosives and narcotics present negligible vapor pressure, (RDX and PETN are 0.0005 ppb and .0015 ppb respectively) it is believed that transport of the material is via micron sized particulates. The narcotics or explosives are present either as particulates or adsorbed onto airborne carriers such as dust. Thus, the need exists to develop particulates for airborne applications as well. Aerosol generation techniques commonly used in air quality research4 will be applied to this problem. These techniques can be exploited as a baseline standard for the assessment and development of vapor/particle contraband detection systems This paper will describe two methods of generating aerosols of contraband materials and the application of these devices to the preparation of standards. The estimated perfonnance of the equipment is based on manufacturers specifications and theory. Experiments are currently being performed at the authors laboratory to evaluate the performance of this equipmen...

EXPLOSIVES DETECTION: A Challenge for Physical Chemistry

“…Davies et al (56) described a development program that applied two sophisticated particle generation techniques: a vibrating orifice aerosol generator (involving evaporation of monodisperse liquid solution droplets) and a fluidized bed generator (which uses dry powder as the feed material). This program responded to a need for better-controlled standard particle sources than those evaluated to that point.…”

Particle Characteristics of Trace High Explosives: RDX and PETN*

“…The particle sizes of feedstock powders of RDX and PETN used in the manufacture of plastic‐bonded explosives can range from nanometers to millimeters depending on the type of crystallization process used. Military specifications for C‐4 require feedstock RDX with a 3:1 mix of two particle sizes with diameters of 850 and 44 μm, respectively (2). When handling C‐4 and Semtex, the main process leading to the presence of particles in residues is probably fragmentation of the crystals, resulting in much smaller particles in the residues than in the parent material.…”

A simple and flexible thin film evaporating device for energetic materials

“…For example, physical vapor deposition 1 ͑PVD͒ or sputter coating techniques work well under vacuum and are often used for metals with high melting points. 12 However, these systems were not used for film deposition and were limited to sensors. This technique is often performed in vacuum ͑ϳ10 −2 torr͒, 2 where the evaporated particles can travel directly to the deposition target without colliding with the background gas.…”