x-rays •

The scientists have successfully developed the world’s sharpest X-ray beam which is ten thousand times thinner than a strand of hair.

Researchers led by Professor Tim Salditt from the University of Gottingen have created the fine beam of X-ray light which is barely 5 nanometres in diameter. The light allows focusing on smallest details. The thickness of the layers is selected in such a way that the bright areas of the diffraction pattern coincide at the same spot.

“Instead of a common lens, we use a so-called Fresnel lens which consists of several layers,” said co-author Dr Markus Osterhoff.

The central support is a fine tungsten wire with the thickness of only a thousandth of a millimetre. Around the wire, nanometre-thin silicon and tungsten layers are applied in an alternating way. The physicists then cut a thin slice from the coated wire.

“This slice has 50 to 60 silicon and tungsten layers, comparable to growth rings of a tree,” said team member Florian Doring.

“And the layer thicknesses have to be extremely precise,” Christian Eberl added. The wire slice with a size of only about two thousandth of a millimeter is used as a lens. However, it does not diffract light like a glass lens but scatters it like an optical grid generating a pattern of bright and dark patches.

On the principle of ‘the more precise the lens is fabricated; the sharper becomes the X-ray focus’, the physicists obtained an X-ray beam of 4.3 nanometers (millionth of a millimeter) diameter in horizontal direction and 4.7 nanometers diameter in vertical direction.

The fine X-ray beam opens up new possibilities for materials science, eg the investigation of nano wires to be used in solar cells.

The study was published in the journal Optics Express.

In an invention that could serve crucial in enhancing the security system and checking terror attacks, the scientists have developed bomb-detecting lasers that are much equipped and advanced than the common x-ray detecting machines in a bid to foil bomb attacks.

Michigan State University researchers have developed a laser that can detect micro traces of explosive chemicals on clothing and luggage.

“Since this method uses a single beam and requires no bulky spectrometers, it is quite practical and could scan many people and their belongings quickly,” Dantus said. “Not only does it detect the explosive material, but it also provides an image of the chemical’s exact location, even if it’s merely a minute trace on a zipper.”

This doesn’t mean that security forces will be armed with handheld laser in airports, however. This laser would more likely be in a conveyor belt, like the X-ray scanners already used for airport security. The low-energy laser is safe to use on luggage as well as passengers, he added.

Scientists have been struggling hard for decades to develop scanning equipments that are powerful enough for detection, but safe enough to use on people.

Dantus’ bomb-detecting laser works as a single beam, but uses two pulses. The first resonates with certain chemical frequencies found in explosives. The second, a shadow pulse, serves as a reference. A discrepancy between the two pulses indicates the presence of explosive materials.

“The laser is not affected by the color or surface of clothes or luggage,” Dantus said.

The Department of Homeland Security funded the research. The research was published in Applied Physics Letters.

Scientists generate world’s sharpest X-ray beam

Scientists develop bomb-detecting lasers that can track bombs, explosives in luggage

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