The millimeter-wave through the terahertz region is now the subject of aggressive university and national laboratory research driven in part by the availability of short-pulse generators, which produce a wide spectrum of frequencies through this region. The experience of the Transportation Security Laboratory (TSL) with these techniques is very limited apart from experience with the Manhattan II projects,6 which were initiated by the TSL. Hence the need for this NRC report.
Based on the state of the art of this technology and on input from the sponsor on how the committee can best address its needs, this report addresses the following four areas:
The physical phenomena limiting or enhancing imaging and spectroscopy performance of millimeter-wavelength and terahertz instrumentation and an assessment of what unique capabilities may result to complement other sensors. These phenomena include the interaction of electromagnetic radiation with the atmosphere, clothing, and explosives.
The state of the art of electronic components in the millimeter-wavelength and terahertz region of the electromagnetic spectrum and what advances will result in the enhanced performance of these components, or may even be the minimum required to provide a useful capability.
Descriptions of the operation of developmental systems, including short-pulse systems and active millimeter-wave passenger scanners.
An implementation strategy for the development of millimeter-wavelength/terahertz technologies for application to aviation security.
While numerous references are cited throughout the report they are not all-inclusive, as the literature on millimeter-wavelength and terahertz technology is voluminous. A recent Internet search on the word “terahertz” alone generated over a million hits, and a formal bibliographic reference search will result in several hundred citations. When reviewing the literature describing the ability of these technologies to find and identify explosives and concealed weapons, the reader must carefully examine the data that are presented and the conclusions that are extracted from the data. In many cases, the information, although correct, may be incomplete and/or misleading.
The combination of a sense of urgency about addressing the emerging terrorist threats and the perceived availability of new funds to bring potential technologies to address these threats has yielded a plethora of technological proposals. Unfortunately, some of these proposals are neither well founded on the principles of physics nor have they been successfully demonstrated by sound experimentation and testing. Some of these proposals also appear to have been driven by exaggerated claims made by others who may lack a sound understanding of the technology and of its strengths and limitations. This situation has resulted in some unsubstantiated and unfulfilled performance expectations regarding the application of some of this antiterrorism