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China to build world's brightest light source facility

China to build world's brightest light source facility. Science & Technology World Website

A file photo shows the Shanghai Synchrotron Radiation Facility (SSRF) project that was put into service on Jan 19, 2010.


China plans to build a next-generation synchrotron radiation facility in Beijing, according to a researcher from Chinese Academy of Sciences, one of the country's top research institutes.

Dong Yuhui, the researcher, said that the project is expected to start construction in Nov next year and will be completed within six years. The total investment will reach 4.8 billion yuan ($698.4 million).

The facility, dubbed Beijing Light Source, will meet the national security demands and create aerospace materials among other products. It will provide high-resolution method to know substantial structures better.

Beijing Light Source will be the so-called fourth generation light source, and its key performance indicators would be higher than the third-generation ones.

It will create the brightest X-rays in the worldwide, 70 times brighter than the US National Synchrotron Light Source II (NSLS-II) and 10 times brighter than Sweden's MAX IV, the strongest of its kind in the world so far.

Bright X-rays could help measure the atomic structure of various substances, and the higher brightness will help people to see more details of substances, something akin to using flashlight to see things, Dong said.

Currently, China has the light sources from first generation to third generation, such as the first-generation facility BSRF in Beijing, the second-generation facility NHLS in Hefei, Anhui province, and the third-generation SSRF in Shanghai.

Around the world, there are more than 50 such facilities providing support in many research fields. The light source plays an important role in the medical field, helping researchers know mechanisms of tumors and cerebrovascular diseases.


Cheap, ultra low-power light source runs on just 0.1 Watts

Cheap, ultra low-power light source runs on just 0.1 Watts Science & Technology World

 

Researchers at Tohoku University in Japan have developed a new low-cost flat panel light source that could pioneer a new generation of brighter, cheaper and greener lighting devices to rival LEDs. The device uses arrays of highly conductive carbon nanotubes to deliver evenly-distributed illumination with high efficiency and a power consumption as low as 0.1 Watts – about 100 times lower than that of light-emitting diodes.

LED lights are renowned for their high efficiencies, but the fact that only a fraction of the photons they produce actually ends up illuminating the surrounding environment suggests that there is still much room for improvement. One alternative approach explored by Prof. Norihiro Shimoi and colleagues was to build a structure based on carbon nanotubes, one-atom thick layers of carbon folded into a cylindrical shape.

This state-of-the-art device has a diode-like structure like LEDs but, curiously enough, the way in which it produces light is actually closer to the cathode ray tubes used in the TVs and computer monitors of the past century. Under the influence of a strong electric field, each carbon nanotube acts as a tiny cathode ray tube that releases a high-speed beam of electrons from its tip. These electrons then hit a phospor screen kept under vacuum and, in the process, release a small amount of energy that causes the phospor to glow.

Building the device was a fairly simple, low-cost process. The researchers started by mixing highly crystalline single-walled carbon nanotubes with an organic solvent and a surfactant compound. They then painted the mixture on the cathode and scratched the surface with sandpaper, which allows the electrons to more easily separate from the tip of the nanotubes.

Their test device needs a high voltage of 5 kV to produce the strong electric field that makes the electron emission mechanism work, but the researchers say the power consumption of the device is actually very low – as little as 0.1 W, which is two orders of magnitude less than LEDs require. This is partly because of the very low resistance posed by carbon nanotubes, and partly because the electron emission mechanism generates beams that are about 1,000 times denser than those in an incandescent light bulb, while also being much more directional and easy to control.

"Many researchers have attempted to construct light sources with carbon nanotubes as field emitter," said Shimoi, "but nobody has developed an equivalent and simpler lighting device."

The scientists say their simple, unoptimized device already achieved a good brightness homogeneity and fairly high lighting efficiency of 60 lumens per watt, which compares to around 100 lm/W for LEDs and 40 lm/W for organic LEDs, or OLEDs. With further development, this holds promise for cheaper, greener, and eventually, brighter devices that could compete with or surpass the performance of LEDs.


First quantum photonic circuit with an electrically driven light source

First quantum photonic circuit with an electrically driven light source. Science & Technology World Website


Whether for use in safe data encryption, ultrafast calculation of huge data volumes or so-called quantum simulation of highly complex systems: Optical quantum computers are a source of hope for tomorrow's computer technology. For the first time, scientists now have succeeded in placing a complete quantum optical structure on a chip, as outlined Nature Photonics. This fulfills one condition for the use of photonic circuits in optical quantum computers.

"Experiments investigating the applicability of optical quantum technology so far have often claimed whole laboratory spaces," explains Professor Ralph Krupke of the KIT. "However, if this technology is to be employed meaningfully, it must be accommodated on a minimum of space." Participants in the study were scientists from Germany, Poland, and Russia under the leadership of Professors Wolfram Pernice of the Westphalian Wilhelm University of Münster (WWU) and Ralph Krupke, Manfred Kappes, and Carsten Rockstuhl of the Karlsruhe Institute of Technology (KIT).

The light source for the quantum photonic circuit used by the scientists for the first time were special nanotubes made of carbon. They have a diameter 100,000 times smaller than a human hair, and they emit single light particles when excited by laser light. Light particles (photons) are also referred to as light quanta. Hence the term "quantum photonics."

That carbon tubes emit single photons makes them attractive as ultracompact light sources for optical quantum computers. "However, it is not easily possible to accommodate the laser technology on a scalable chip," admits physicist Wolfram Pernice. The scalability of a system, i.e. the possibility to miniaturize components so as to be able to increase their number, is a precondition for this technology to be used in powerful computers up to an optical quantum computer.

As all elements on the chip now developed are triggered electrically, no additional laser systems are required any more, which is a marked simplification over the optical excitation normally used. "The development of a scalable chip on which a single-photon source, detector, and waveguide are combined, is an important step for research," emphasizes Ralph Krupke, who conducts research at the KIT Institute for Nanotechnology and the Institute of Materials Science of the Darmstadt Technical University. "As we were able to show that single photons can be emitted also by electric excitation of the carbon nanotubes, we have overcome a limiting factor so far preventing potential applicability."

About the methodology: The scientists studied whether the flow of electricity through carbon nanotubes caused single light quanta to be emitted. For this purpose, they used carbon nanotubes as single-photon sources, superconducting nanowires as detectors, and nanophotonic waveguides. One single-photon source and two detectors each were connected with one waveguide. The structure was cooled with liquid helium to allow single light quanta to be counted. The chips were produced in an electron beam scribing device.

The scientists' work is fundamental research. It is not yet clear whether and when it will lead to practical applications. Wolfram Pernice and the first author, Svetlana Khasminskaya, were supported by the Deutsche Forschungsgemeinschaft and the Helmholtz-Gemeinschaft, Ralph Krupke was funded by the Volkswagen Foundation.

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