Gwyn Williams holding a 5-cell cavity inside JLab's FEL

Gwyn Williams holding a 5-cell cavity inside JLab's FEL.

Illuminating idea: Lab's T-light work may have uses in medicine, security

By Dave Schleck, Daily Press
November 15, 2002

You can't see it. But it could brighten the way for new tools in medicine and terrorism defense.

A Jefferson Lab scientist has produced record amounts of an invisible kind of light that could someday detect everything from anthrax to guns to skin cancer.

Scientists have known for more than a century about terahertz light, located on the light spectrum between television waves and visible rays. But until now, they've produced it only in small amounts. Gwyn Williams, a researcher of light at Jefferson Lab, led an experiment that generated terahertz rays 20,000 times stronger than previous attempts.

"In my view, there's nothing clever about this experiment. But I did it," said Williams. "This is the only place in the world where it can be done."

The experiment took place at Jeff Lab's free-electron laser in November 2001. Williams held off the announcement until today, when it is published in Nature magazine. The free-electron laser produces light useful for commercial, science and defense applications.

For this experiment, a portion of the laser sent a focused beam of electrons at nearly the speed of light through a magnetic field, which generated terahertz light, or T-light.

Williams, a 55-year-old native of England who came to Jefferson Lab in March 2000, worked with scientists and used additional equipment from two other Department of Energy labs - Brookhaven National Laboratory in New York and Lawrence Berkeley National Laboratory in California.

They produced 20 watts of T-light. The previous record was 2/1000 of a watt. That's similar to the difference between a spotlight and a candle, Williams said.

Williams, who has seven coffee mugs scattered about his cubicle, didn't need any java to stay perky during the 48-hour experiment. "Everybody was very excited," said Williams, who has been studying light for more than three decades. "There was more adrenaline flowing than caffeine."

A few hospitals have used small amounts of terahertz light in medical tests. But the dim light wasn't as effective as a stronger beam would be. Now, with a much brighter light, Williams envisions doctors using tabletop T-light scanners to check patients for skin cancer. A sophisticated camera would have to be developed to allow researchers to use terahertz light, which is not visible to the eye.

"If I were looking at you in terahertz light, I would know if you have any cancer on your skin," said Williams, who is the basic research project manager at the free-electron laser.

Different types of cancer, viruses and bacteria absorb T-light in unique ways, which could help doctors or even security forces pinpoint biological threats. T-light devices could fingerprint chemical and biological terror materials in envelopes, Williams said.

"You could screen mail, you could screen passengers," Williams said. T-light does not go through metal, which means terahertz devices could detect knives, guns and other weapons. "I would love if it could detect mines in the sand, because a lot of people are maimed by those," Williams said.

There are limitations. Since terahertz light does not go through metal, it cannot be used to inspect container ships for dangerous cargo. It may take two years for a company to develop a tabletop T-light device, Williams said. Jefferson Lab is seeking a patent. Williams said he is looking forward to companies requesting permission to use the technology.

Scientists outside the research team commended Williams but cautioned against calling his research a discovery. "This is a wonderful new tool for science," said Hans C. von Baeyer, chancellor professor of physics at the College of William and Mary. "Building a new tool and making a new discovery is something different."

Linda Ware, public affairs manager at Jefferson Lab, described the experiment as a byproduct of the work that goes on every day at the lab. "It's just another tool in the toolbox," she said.