Keep your shoes on: T-rays can see right through

CHICAGO, Nov 28 (Reuters) Imagine a trip to the airport without having to slip off your shoes.

A scanner using T-rays, a harmless form of electromagnetic radiation, could make that possible, researchers at the US Department of Energy's Argonne National Laboratory said yesterday.

''At airports we have to take off our shoes,'' Ulrich Welp of Argonne's Materials Science Division said in a telephone interview.

''It is kind of a nuisance.'' Using T-rays, it would be possible to examine travelers' shoes without the need to disrobe, he said.

T-rays have been difficult to generate without using a host of bulky equipment. But researchers at Argonne have found a simple way to generate T-rays -- terahertz radiation -- using special, high-temperature superconducting crystals in a compact device.

''We developed a new source for terahertz radiation,'' Welp said. The work, done with researchers in Turkey and Japan, represents ''a big step forward,'' he said.

T-rays are part of the electromagnetic spectrum that lies between microwaves on the low end and infrared radiation on the high end.

Unlike conventional X-rays, which can cause cell damage, T-rays do not have enough energy to alter cell ionization, which can lead to radiation sickness or cancer.

And while they cannot see through metals or water, they can penetrate many common materials like leather, fabric, cardboard and paper.

''Terahertz radiation is sensitive to characteristics of a lot of chemicals,'' Welp said, offering the promise of new uses in airport scanners or detecting illicit chemicals or weapons that could not be picked up by an X-ray.

T-rays can also penetrate about four-tenths of an inch (1 cm) through human skin, offering some medical applications as well.

''Tests have shown this could be a viable diagnostic tool for skin cancer and the spread of skin cancer under the surface of the skin. You could diagnose without having to do an operation,'' Welp said.

''It has been demonstrated that it can detect tooth decay without having to take an X-ray,'' he said.

Welp said he and colleagues still have a lot of fine-tuning to do, but the discovery offers a lot of promise.

REUTERS ARB BST0839