1. The technology base for millimeter-wavelength/terahertz security screening is expanding rapidly internationally, yet there is insufficient technology available to develop a system capable of identifying concealed explosives.

  2. Millimeter-wavelength/terahertz technology has potential for contributing to overall aviation security, but its limitations need to be recognized. It will be most effective when used in conjunction with sensor technologies that provide detection capabilities in additional frequency regions.

  3. Millimeter-wavelength/terahertz technology in portal applications has been demonstrated for detecting and identifying objects concealed on people.

  4. Millimeter-wavelength/terahertz image quality raises personal privacy issues that need to be addressed.

  5. Millimeter-wavelength/terahertz technology and x-rays provide images of similar quality. However, millimeter-wavelength/terahertz energy has the safety benefit of being non-ionizing radiation, while x-rays are ionizing radiation. Millimeter-wavelength/terahertz energy cannot penetrate metal objects.

  6. Universities, national laboratories, and the commercial sector (both national and international businesses) continue to increase investment in millimeter-wavelength/terahertz technologies for security, medical, nondestructive inspection, and manufacturing quality-control applications.

  7. A decision by the TSA to invest in an imaging portal depends on the potential threat posed by passengers carrying either weapons or explosives or other material. The cost of a system, the probability of detection, the false-alarm rate, and the throughput versus that of a competing x-ray system would impact the management decision.


Building on the conclusions presented above, the committee makes the following recommendations to the Transportation Security Administration regarding the application of millimeter-wavelength/terahertz technology to security screening.

  1. To perform an accurate assessment of the applicability of millimeter-wavelength/terahertz-based technology to explosive detection, the TSA will need to do the following: (1) decide on the range of materials to be detected, (2) assess the state of knowledge of what chemical structures and/or features of the scope of materials lend themselves to detection by millimeter-wavelength/terahertz-based spectroscopy, (3) assess the presence of these features in other common materials (such as clothing) within the range of uncertainty for such features, and (4) assess the contribution of additives to explosives to the millimeter-wavelength/terahertz signature.

  2. The TSA should examine how millimeter-wavelength/terahertz technology can be employed with other technologies to enhance the detection of weapons and explosives.

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