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Particle accelerator that can fit on a tabletop opens new chapter for science research

Particle accelerator that can fit on a tabletop opens new chapter for science research | Technology | Scoop.it

Physicists at The University of Texas at Austin have built a tabletop particle accelerator that can generate energies and speeds previously reached only by major facilities that are hundreds of meters long and cost hundreds of millions of dollars to build."We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch," said Mike Downer, professor of physics in the College of Natural Sciences. "Until now that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It's a downsizing of a factor of approximately 10,000."The results, which were published this week in Nature Communications ("Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV"), mark a major milestone in the advance toward the day when multi-gigaelectronvolt (GeV) laser plasma accelerators are standard equipment in research laboratories around the world.


Via Dr. Stefan Gruenwald
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Light wheel - new type of light wave extends the possibilities in nanotechnology

Light wheel - new type of light wave extends the possibilities in nanotechnology | Technology | Scoop.it

Propeller or wheel? In circularly polarized light, the vector which represents the electric field of the light wave (blue arrows in above figure) rotates helically in the direction of propagation. Such an electromagnetic wave has longitudinal angular momentum. If two circularly polarised waves rotating in opposite directions meet at a focal point, light with purely transverse angular momentum is generated. Its electric field vector rotates about an axis perpendicular to the direction of propagation like a bicycle spoke.

Light in general can exert incredible forces. According to the rules of quantum mechanics, light is an electromagnetic wave, as well as a stream of photons. Since it has momentum, a transparent particle through which a light beam falls experiences a recoil when the photons leave it. Although the force which a photon exerts in this process is almost infinitesimal, the effect of innumerable light particles in intense and tightly focused laser beams adds up in such a way that objects up to a few micrometres can be held in an optical trap or moved in a specific way. Biologists, for example, use this effect in optical tweezers to fix cells and rotate them at the focus of a microscope. To this effect, scientists working with Gerd Leuchs, Director at the Max Planck Institute for the Science of Light, are now creating new possibilities for them.

 

The team has created a photonic wheel, i.e. light with purely transverse angular momentum: the electric field of the electromagnetic wave rotates about an axis whose orientation is perpendicular to the direction of motion, just like the axis of a wheel. Until now, physicists have mainly been familiar with light with longitudinal angular momentum where the electric field rotates like a propeller around an axis aligned along the direction of motion. “The possibility that light can have purely transverse angular momentum when averaged over the complete cross-section of the beam had not been realised before,” says Peter Banzer, who made a significant contribution to the discovery.

 

This is because, as the Erlangen-based physicists have now shown both theoretically and practically, it is indeed possible to generate light with purely transverse angular momentum - and what’s more it is surprisingly easy to do so. “Once it’s down on paper, it looks easy,” says Gerd Leuchs. But somebody has to come up with the idea in the first place. The researchers are now developing this idea using circularly polarised light. A wave of circularly polarised light turns like a screw around the direction of beam propagation and has propeller-like longitudinal angular momentum. Light with circular polarisation can be generated with the aid of a birefringent crystal, for example.


Via Dr. Stefan Gruenwald
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Ivan Koh's curator insight, June 30, 2013 5:47 PM

This article is about telling that using light manipulation, we may be able to utilise nanotechnology. It goes down into the scientific terms of how its done and how it can be used to benefit other things. I think the factors leading to the realization of reaching the possibilities is mostly still limited to science. One may come up with an idea but if it cannot be proven theoretically or scientifically, then its still far from being a possibility.
I wonder then how some science discovery and breakthrough happened through accidents.