Argonne beam source may speed searches
Harmless electromagnetic radiation beams could replace X-rays at airport security posts, enabling passengers to pass inspection quickly without shedding shoes, belts and pocket change.
T-rays, or terahertz radiation, penetrate clothing and some other materials but they don’t go through metals or travel deeply inside the human body. While X-rays work by penetrating human tissue and other materials, creating images, T-rays create molecular “fingerprints” of materials they encounter. In theory T-rays should identify explosives carried in a piece of luggage.
And T-rays, like radio waves and visible light, pose no human health risk because they don’t ionize materials they encounter, as X-rays do.
Scientists use T-rays in research, but they have been limited mostly to laboratory settings because there has been no way to generate them cheaply. A research team at Argonne National Laboratory recently raised hopes for commercial applications by successfully generating T-rays from tiny crystals of high-temperature superconductors.
“There’s been a race,” said Ken Gray, an Argonne scientist. Large groups of T-ray researchers in Japan and Germany were astonished in October when they learned of Argonne’s success, Gray said.
Although only a tiny speck barely large enough to see, the layered crystal Argonne scientists used to generate T-rays is much larger than what their international competitors were using, said Wai-Kwong Kwok, another member of the Argonne team.
“The prediction was that you wouldn’t get T-ray emissions from larger crystals,” Kwok said. “We looked at the theories and wondered why was it not working?”
The key to their success, said Ulrich Welp of Argonne’s materials science team, is tiny cavities in the crystals that generate T-rays when weak alternating electric current passes through them. The scientists shaped and arranged the cavities so the oscillations generated by the current would synchronize and amplify one another.
“That’s been the challenge all along,” Welp said. “If one junction oscillates up while another junction oscillates down, they’ll cancel each other out and you won’t get anything.”
Their discovery drew interest from commercial firms and the Department of Defense, said Welp. Besides raising T-ray output, the team needs to find a way to tune the rays to different terahertz frequencies, giving them the ability to identify a variety of materials.
Potential commercial partners and the military “would like a demonstration. They’d like us to identify explosives,” said Gray. “We’re not there yet, but we’re exploring several avenues to get us there.”
If the researchers can show that T-rays identify explosives and attract hoped-for federal grants and private investment, the technology could be ready for commercialization in three to five years, Welp said.
The Argonne researchers have applied for a patent on their discovery and are working to improve the device’s efficiency. The scientists know they are getting only a fraction of the potential T-ray energy the crystal can produce.
Using T-rays at airport security stations raises some privacy issues for people concerned that the technology might be used to look through a person’s clothing, undressing them visually, but Gray said that is not easily done.
“Your imagination does a much better job,” he said.
More likely the equipment would use T-rays to feed information into a computer for analysis. Most passengers would pass through an inspection quickly and a few would be singled out by the computer for closer inspection by a human. Such inspections could be triggered, for example, if a tube of toothpaste a passenger carried had a molecular fingerprint similar to an explosive’s.
Metal detectors and X-ray machines along with humans looking at images of every piece of luggage in search of suspicious materials would be phased out if T-rays can meet their potential.
Costs are difficult to estimate so early in the process, but the scientists said T-ray-based technology would cost less than today’s X-ray-based equipment because the underlying solid-state technology is cheaper to produce.
If they can be generated as cheaply as the Argonne researchers predict, T-rays would probably be applied to products beyond security systems. They might be used to diagnose certain kinds of skin cancer and used in dental offices to identify tooth decay, replacing X-rays in some cases.
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jvan@tribune.com
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About T-rays, terahertz radiation
- T-rays are a safe form of electromagnetic radiation. They do not have sufficient energy to cause cellular damage that can lead to cancer.
- The rays do not penetrate through metal but do penetrate materials such as leather, fabric and paper.
- Unlike X-rays, T-rays should be able to identify a wider range of hazardous materials, such as explosives and illegal substances.
Source: The Chicago Tribune.