'Particle accelerator on a chip' uses simple silica glass and IR laser

Julien Happich -October 02, 2013

Researchers from the U.S. Department of Energy's (DOE) SLAC National Accelerator Laboratory and Stanford University have developed a nanostructured silica-based "particle accelerator on a chip" which relies on an infrared laser to accelerate electrons at a rate 10 times higher than conventional technology.

This could dramatically shrink particle accelerators for science and medicine applications. "We still have a number of challenges before this technology becomes practical for real-world use, but eventually it would substantially reduce the size and cost of future high-energy particle colliders for exploring the world of fundamental particles and forces," said Joel England, the SLAC physicist who led the experiments. "It could also help enable compact accelerators and X-ray devices for security scanning, medical therapy and imaging, and research in biology and materials science."

Because it employs commercial lasers and low-cost, mass-production techniques, the researchers believe it will set the stage for new generations of "tabletop" accelerators. At its full potential, the new "accelerator on a chip" could match the accelerating power of SLAC's 2-mile-long linear accelerator in just 100 feet (of stacked devices), and deliver a million more electron pulses per second.

Just 3 mm long, this nanostructured silica-based "particle accelerator on a chip" relies on an infrared laser to accelerate electrons at a rate 10 times higher than conventional technology.

The initial prototype achieved an acceleration gradient, or amount of energy gained per length, of 300 million electronvolts per meter. That's roughly 10 times the acceleration provided by the current SLAC linear accelerator.

"Our ultimate goal for this structure is 1 billion electronvolts per meter, and we're already one-third of the way in our first experiment," said Stanford Professor Robert Byer, the principal investigator for this research.

Particles are generally accelerated in two stages (see video animation below). First they are boosted to nearly the speed of light. Then any additional acceleration increases their energy, but not their speed; this is the challenging part. In the accelerator-on-a-chip experiments, electrons are first accelerated to near light-speed in a conventional accelerator. Then they are focused into a tiny, half-micron-high channel within a fused silica glass chip just half a millimeter long. The channel had been patterned with precisely spaced nanoscale ridges. Infrared laser light shining on the pattern generates electrical fields that interact with the electrons in the channel to boost their energy.

Accelerator on a Chip: How It Works (video, 1:36)

Accelerator on a Chip: How it was Fabricated (video, 1:51)

Turning the accelerator on a chip into a full-fledged tabletop accelerator will require a more compact way to get the electrons up to speed before they enter the device. A collaborating research group in Germany, led by Peter Hommelhoff at Friedrich Alexander University and the Max Planck Institute of Quantum Optics, has been looking for such a solution. It simultaneously reports in Physical Review Letters its success in using a laser to accelerate lower-energy electrons.

For more, see the article ("Demonstration of electron acceleration in a laser-driven dielectric microstructure") published in the journal Nature.

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