T射线或取代X射线来探测不透明物

"T-rays" may make X-rays obsolete¹废弃，淘汰 as a means of detecting bombs on terrorists or illegal drugs on traffickers, among other uses, contends竞争，主张 a Texas A&M physicist² who is helping³ lay the theoretical groundwork to make the concept a reality. In addition to being more revealing than X-rays in some situations, T-rays do not have the cumulative累积的 possible harmful effects. Alexey Belyanin focuses his research on terahertz兆赫, otherwise known as THz or T-rays, which he says is the most under-developed and under-used part of the electromagnetic spectrum电磁谱. It lies between microwave radiation and infrared⁶ (heat) radiation.

Belyanin, associate professor in the Texas A&M Physics Department, has collaborated⁷ with colleagues at Rice University and the National High Magnetic Field Laboratory to publish findings about their T-ray research in the renowned⁸ journal "Nature Physics."

"THz radiation can penetrate⁹ through opaque¹⁰不透明物 dry materials. It is harmless and can be used to scan humans," Belyanin says. "Unfortunately, until recently the progress in THz technology has been hampered限制，阻碍 by a lack of suitable sources and detectors¹²."

Belyanin and his team have offered hope: The researchers are able to control the T-rays by varying external parameters¹³参数，参量 like temperature or magnetic field, making it possible to build THz sensors¹⁴, cameras and other devices.

Traditionally, powerful photons光子 from visible or near-infrared laser pulses are used to probe semiconductors¹⁵, knocking electrons out of the atoms. Belyanin and collaborators use the less powerful T-rays instead, which only excite the waves in the electron gas because T-rays do not have enough energy to knock out electrons.

"This is as if instead of throwing a stone into a tank of water, which would create a lot of splashes, we gently vibrate one wall of the tank, sending a sound wave through the body of water and ripples¹⁶ over its surface," he explains.

By varying temperature and the magnetic field磁场, scientists can tune¹⁷ the pulses and observe the behavior of the waves.

"This provides extremely valuable and unique information about the properties of the material, just like seismic¹⁸ waves地震波 tell you what is in the Earth's interior," the Texas A&M physicist points out.

"The highlight of our results is observations of interference of magnetoplasmons. By tiny changes in the applied¹⁹ magnetic field or temperature, we can make plasma²⁰ waves等离子体波 amplify²¹放大，增强 or cancel each other. This makes the whole sample either completely opaque or transparent²² to the incident THz radiation."

Belyanin believes the technology has important practical implications, such as in security work.

"Using THz cameras, we could detect weapons or drugs concealed隐蔽的，隐匿的 on a human body, or look inside envelopes and boxes," he says. There are many other applications for THz radiation, including material studies, chemistry, biology and medicine."