Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New T-ray source could improve airport security, cancer detection

29.11.2007
Going through airport security can be such a hassle. Shoes, laptops, toothpastes, watches and belts all get taken off, taken out, scanned, examined, handled and repacked. But "T-rays", a completely safe form of electromagnetic radiation, may reshape not only airport screening procedures but also medical imaging practices.

Scientists at the U.S. Department of Energy's Argonne National Laboratory, along with collaborators in Turkey and Japan, have created a compact device that could lead to portable, battery-operated sources of T-rays, or terahertz radiation. By doing so, the researchers, led by Ulrich Welp of Argonne's Materials Science Division, have successfully bridged the "terahertz gap" – scientists' name for the range of frequencies between microwaves (on the lower side) and infrared (on the higher side) of the electromagnetic spectrum.

While scientists and engineers have produced microwave radiation using conventional electric circuits for more than 50 years, Welp said, terahertz radiation could not be generated that way because of the physical limitations of the semiconducting circuit components.

"Right around 1 terahertz, you have a range of frequencies where there have never been any good solid-state sources," he added. "You can make those frequencies if you are willing to put together a whole table full of expensive equipment, but now we've been able to make a simple, compact solid-state source."

Unlike far more energetic X-rays, T-rays do not have sufficient energy to "ionize" an atom by knocking loose one of its electrons. This ionization causes the cellular damage that can lead to radiation sickness or cancer. Since T-rays are non-ionizing radiation, like radio waves or visible light, people exposed to terahertz radiation will suffer no ill effects. Furthermore, although terahertz radiation does not penetrate through metals and water, it does penetrate through many common materials, such as leather, fabric, cardboard and paper.

These qualities make terahertz devices one of the most promising new technologies for airport and national security. Unlike today's metal or X-ray detectors, which can identify only a few obviously dangerous materials, checkpoints that look instead at T-ray absorption patterns could not only detect but also identify a much wider variety of hazardous or illegal substances.

T-rays can also penetrate the human body by almost half a centimeter, and they have already begun to enable doctors to better detect and treat certain types of cancers, especially those of the skin and breast, Welp said. Dentists could also use T-rays to image their patients' teeth.

The new T-ray sources created at Argonne use high-temperature superconducting crystals grown at the University of Tsukuba in Japan. These crystals comprise stacks of so-called Josephson junctions that exhibit a unique electrical property: when an external voltage is applied, an alternating current will flow back and forth across the junctions at a frequency proportional to the strength of the voltage; this phenomenon is known as the Josephson effect.

These alternating currents then produce electromagnetic fields whose frequency is tuned by the applied voltage. Even a small voltage – around two millivolts per junction – can induce frequencies in the terahertz range, according to Welp.

Since each of these junctions is tiny – a human hair is roughly 10,000 times as thick – the researchers were able to stack approximately 1,000 of them on top of each other in order to generate a more powerful signal. However, even though each junction would oscillate with the same frequency, the researchers needed to find a way to make them all radiate in phase.

"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."

In order to synchronize the signal, Argonne physicist Alexei Koshelev suggested that the stacks of Josephson junctions should be shaped into resonant cavities, which visiting scientist Lufti Ozyuzer of the Izmir Institute of Technology, Turkey, and graduate student Cihan Kurter then fashioned. When the width of the cavities was precisely tuned to the frequencies set by the voltage, the natural resonances of the structure synchronized the oscillations and thus amplified the T-ray output, in a method similar to the production of light in a laser.

"Once you apply the voltage," Welp said, "some junctions will start to oscillate. If those have the proper frequency, an oscillating electric field will grow in the cavity, which will pull in more and more and more of the other junctions, until in the end we have the entire stack synchronized."

By keeping the length and thickness of the cavities constant while varying their width between 40 and 100 micrometers, the researchers were able to generate frequencies from 0.4 to 0.85 terahertz at a signal power of up to 0.5 microwatts. Welp hopes to expand the range of available frequencies and to increase the strength of the signal by making the Josephson cavities longer or by linking them in arrays.

"The more power you have, the easier it is to adopt this technology for all sorts of applications," he said. "Our data indicate that the power stored in the resonant cavities is significantly larger than the detected values, though we need to improve the extraction efficiency. If we can get the signal strength up to 1 milliwatt, it will be a great success."

Collaborators on this research were Lutfi Ozyuzer, Alexei Koshelev, Cihan Kurter, Nachappa (sami) Gopalsami, Qing'An Li, Ken Gray, Wai-Kwong Kwok and Ulrich Welp of Argonne; Masashi Tachiki from the University of Tokyo; Kazuo Kadowaki, Takashi Yamamoto, Hidetoshi Minami and Hayato Yamaguchi from the University of Tsukuba; and Takashi Tachiki from the National Defense Academy of Japan.

The research was supported by DOE's Office of Basic Energy Sciences and by Argonne's Laboratory Directed Research and Development funds.

A scientific paper based on their research, "Emission of Coherent THz Radiation from Superconductors," appears in the November 23 issue of Science.

Argonne National Laboratory, a renowned R&D center, brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

Steve McGregor | EurekAlert!
Further information:
http://www.anl.gov

More articles from Power and Electrical Engineering:

nachricht Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH

nachricht To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>