SLAC National Accelerator Laboratory researchers have successfully used a laser to accelerate electrons at a rate 10 times higher than conventional technology -- and in a glass chip smaller than a grain of rice.
If researchers successfully refine the laser-driven particle accelerator, the 2-mile long linear accelerator at the SLAC National Accelerator Laboratory could become a thing of the past, they said.
The achievement was published today, Sept. 27 in the science journal Nature. The team includes scientists from the U.S. Department of Energy's SLAC National Accelerator Laboratory and Stanford University.
Advancement of the new technology to practical purposes still has a way to go, but it isn't light years away.
"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. 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," said Joel England, the SLAC physicist who led the experiments.
The technology employs commercial lasers and low-cost, mass-production techniques, and 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 -- and deliver a million more electron pulses per second, the researchers said.
The initial demonstration achieved an acceleration that is roughly 10 times what is currently provided by the 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," Stanford Professor Robert Byer, research principal investigator, said.
Accelerators currently use microwaves to boost the energy of electrons. Researchers have been looking for more economical alternatives, and this new technique, which uses ultra-fast lasers to drive the accelerator, is a leading candidate, they said.
Particles are generally accelerated in two stages: they are boosted to nearly the speed of light, then any additional acceleration increases their energy. But the current method does not increase their speed.
The accelerator-on-a-chip experiment continues that rapid-speed increase. The electrons are first accelerated to near light-speed in a conventional accelerator, then they are focused into a tiny, half-micron-high channel within the glass chip, which is just a half-millimeter long.
The channel is patterned with precisely spaced miniscule ridges. Infrared laser light shining on the pattern generates electrical fields that interact with the electrons in the channel to boost their energy, according to the researchers.
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, however.
A collaborating research group in Germany, led by Peter Hommelhoff at the Max Planck Institute of Quantum Optics, has been looking for such a solution. Researchers there simultaneously report in the publication Physical Review Letters that they have successfully used a laser to accelerate lower-energy electrons.
The new particle accelerators could be used well beyond particle physics research. Laser accelerators could be used in small, portable X-ray machines to improve medical care for people injured in combat and provide more affordable medical imaging for hospitals and laboratories.
Stanford graduate students Edgar Peralta and Ken Soong created the patterned-glass chip at the Stanford Nanofabrication Facility. SLAC's Next Linear Collider Test Accelerator was employed for the acceleration experiments. Researchers from the University of California-Los Angeles and Tech-X Corp. in Boulder, Colo. also contributed to the project.
The U.S. Department of Energy provided primary funding, with additional funds from the DOE's Office of Science. Defense Advanced Research Projects Agency's (DARPA) Advanced X-Ray Integrated Sources (AXiS) program.