<title>THz standoff detection and imaging of explosives and weapons (Invited Paper)</title>

Abstract

ABSTRACT Recently, there has been a significant interest in employing Terahertz (THz) technology, spectroscopy and imaging for standoff detection applications. There are three prime motivations for this interest: (a) THz radiation can detect concealed weapons since many non-metallic, non-polar materials are transparent to THz radiation, (b) target compounds such as explosives, and bio/chemical weapons have characteristic THz spectra that can be used to identify these compounds and (c) THz radiation poses no health risk for scanning of people. This paper will provide an overview of THz standoff detection of explosives and weapons including discussions of effective range, spatial resolution, and other limitations. The THz approach will be compared to alternative detection modalities such as x-ray and millimeter wave imaging. Keywords: Terahertz, imaging, stand-off, explosive, weapon, interferometric, synthetic aperture 1. INTRODUCTION Over the past several years, there has been an increased interest in the potential of terahertz (THz) detection for imaging of concealed weapons, explosives, chemical and biological agents. There are three major factors contributing to this interest: (a) Terahertz radiation is readily transmitted most non-metallic and non-polar mediums, thus enabling THz systems to see through concealing barriers such as packaging, corrugated cardboard, clothing, shoes, bookbags, etc. in order to probe the potentially dangerous materials contained within. (b) Many materials of interest for security applications including explosives, chemical agents, and biological agents have characteristic THz spectra that can be used to fingerprint and thereby identify these concealed materials. For example, many explosives (for example C-4, HMX, RDX, TNT) have characteristic transmission/ reflection spectra in the THz range