Particle Characteristics of Trace High Explosives: RDX and PETN^*

Abstract

The sizes of explosives particles in fingerprint residues produced from C-4 and Semtex-1A were investigated with respect to a fragmentation model. Particles produced by crushing crystals of RDX and PETN were sized by using scanning electron microscopy, combined with image analysis, and polarized light microscopy was used for imaging and identifying explosive particles in fingerprint residues. Crystals of RDX and PETN fragment in a manner that concentrates mass in the largest particles of the population, which is common for a fragmentation process. Based on the fingerprints studied, the particle size to target for improving mass detection in fingerprint residues by ion mobility spectrometry (IMS) is > or = 10 microm in diameter. Although particles smaller than 10 microm in diameter have a higher frequency, they constitute < 20% of the total mass. Efforts to improve collection efficiency of explosives particles for detection by IMS, or other techniques, must take into consideration that the mass may be concentrated in a relatively few particles that may not be homogeneously distributed over the fingerprint area. These results are based on plastic-bonded explosives such as C-4 that contain relatively large crystals of explosive, where fragmentation is the main process leading to the presence of particles in the fingerprint residues.

Ion spectrometric detection technologies for ultra‐traces of explosives: A review

“…In conclusion, hair seems to be a suitable surface for explosive detection (Oxley et al, 2008). Studies on the optimization of IMS detection include collection efficiency for different particle sizes of TNT and a comparison of fingerprint and dry Teflon sampling systems of C4 containing RDX (Phares et al, 2000), the sizes of explosive residues prior to IMS analysis (Verkouteren, 2007), and the detection of smokeless powder from various surfaces like CD's and book covers (Colón et al, 2002) have been carried out.…”

A Streamlined, High-Volume Particle Impactor for Trace Chemical Analysis

“…Working with bulk contraband materials (i.e., creating improvised explosive devices or handling illicit narcotics) is expected to contaminate the body, clothing, and surrounding surfaces with micrometer-sized particles of the contraband material (Verkouteren 2007). During trace detection screening, one attempts to collect and interrogate a representative sample from an object and detect any contraband that is present.…”

“…Of particular interest is the ability to collect airborne particles that range from 10 to 30 μm, as this particle diameter range is typically found in explosive contamination left on surfaces of interest (Verkouteren 2007). The ability to rapidly analyze the collected sample is also an essential aspect of this prototype impactor design.…”

Detection of explosives by differential hyperspectral imaging

“…This means being able to sense a few tens of micrometer size diameter particles 15 weighing between one and a few tens of nanograms. In order to attain such sensitivity, one could increase the intensity from the light source, for example, using more efficient optics (i.e., custom designed) or a more powerful source, or increase the size of the collection optics, thus increasing the photon flux going to the camera.…”