T-rays: a new imaging field

T-rays are teraherz rays, and operate between 0.1 to 10 THz which means that they exist between the microwave and infrared frequencies of the optical spectrum. They appear best suited for medical imaging systems and to some extent hazardous material detection. Additionally, they promise a potentially much wider bandwidth for wireless communication applications. T-rays can penetrate paper and cardboard, wood and masonry, plastics and ceramics as well as cloud and fog but they cannot see into water or metals. The energies of THz radiation are a million times weaker than those of X-rays, making them much safer for diagnostic imaging. Furthermore, T-rays are non-ionizing.

Notwithstanding the fact that objects at room temperature emit thermal energy in the THz range it is only recently that suitable radiation sources and detection techniques for practical applications of teraherz wavelengths have been developed. It is by way of research in the field of materials sciences that the right compounds for the manufacture of emitters and detectors are now seeing manufacture. Scientists at the Terahertz Research Center at Rensselaer University were the first to begin using zinc-tellurium crystals as pulsed THz wave sensors under the leadership of Xi-Cheng Zhang, physicist and engineer.

Teraherz radiation can be manipulated like light waves. The European Space Agency has developed a T-ray camera that can see through clothing. There is a utilitarian benefit in the ability to detect concealed weapons or explosives which a person might be harboring under his or her clothes. Detection can occur at far range up to a hundred meters so the procedure can be completely transparent (pun intended).

Research at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility in Newport News, Virginia has developed a technique for producing higher energy T-rays than ever before which involves streaming electrons at near-light speeds through a magnetic field. The electrons emit teraherz vibrations under these conditions. The energies achieved at this level compared to previous T-ray emission sources are akin to comparing floodlights to candles.

T-rays cannot penetrate deeply enough in the human body to replace X-rays but the potential range of applications is far wider.