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We demonstrate a large area time domain terahertz (THz) imaging system capable of scanning 1 meter square area in less than 20-100 minutes for several security applications. The detection of concealed explosives; metallic and non-metallic weapons (such as ceramic, plastic or composite guns and knives); and flammables in luggage, packages and personnel has been demonstrated. Transmission mode images of luggage containing threat items are discussed. Reflection mode images of luggage and personnel are discussed. Time domain THz images can be analyzed for 3 dimensional and volumetric information. Time domain THz images have advantages over coherent narrow band imaging methods, with freedom from interference artifacts and with greater ability to discard irrelevant or intervening reflections through time discrimination. [ABSTRACT FROM AUTHOR]

Terahertz (THz) imaging is being adopted for non-destructive evaluation (NDE) applications in aerospace and other government and industrial settings[1-3]. NASA is currently employing THz reflection NDE to examine the space shuttle external tank sprayed on foam insulation (SOFI) for voids and disbonds. Homeland security applications such as the inspection of personnel[2], the detection of concealed explosives[2], biological agents, chemical weapons, flammables, metallic and non-metallic weapons, and other potentially dangerous items are the subject of active investigation. Advancement of many of these applications beyond small table top experimentation had been limited by slow imaging speed (tens of minutes or hours), small scan areas (<10 square cm) and in many cases the requirement that the sample itself be mechanically raster scanned. We report the development and applications of a high-speed large-area time domain terahertz non-destructive evaluation imaging system. [ABSTRACT FROM AUTHOR]