Particle accelerators the size of a computer chip may be a reality in the near-future thanks to new research from the US Department of Energy’s SLAC National Accelerator Laboratory and Stanford University — researchers there recently succeeded in accelerating electrons at a rate 10 times higher than with conventional technology, simply by aiming a laser into a tiny, specially designed nanostructured glass chip. The researchers think that this new work could have important implications for the scientific and medical communities.
“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,” stated Joel England, the SLAC physicist who led the experimental part of the research. “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.”
As the technology relies only on commercially available lasers, and low-cost, mass-production techniques, the researchers think that it “sets the stage”, so to speak, for new generations of “tabletop” accelerators.
The new technology, despite its miniature size, is impressively powerful — at full potential the new “accelerator on a chip” can equal the accelerating power of SLAC’s 2-mile-long linear accelerator in just 100 feet, while at the same time delivering a million more electron pulses per second.
“This initial demonstration 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,” stated Stanford Professor Robert Byer, the principal investigator for this research.
The press release from the DOE/SLAC National Accelerator Laboratory provides more:
Today’s accelerators use microwaves to boost the energy of electrons. Researchers have been looking for more economical alternatives, and this new technique, which uses ultrafast lasers to drive the accelerator, is a leading candidate. Particles are generally accelerated in two stages. 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.
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 the Max Planck Institute of Quantum Optics, has been looking for such a solution — which it has now found: using a laser to accelerate lower-energy electrons.
Potential applications for this new technology include: compact X-ray free-electron lasers; small, portable X-ray sources to improve medical care for people injured in combat, as well as provide more affordable medical imaging for hospitals and laboratories;
Applications such as those are why this research was partially funded by the Defense Advanced Research Projects Agency’s (DARPA) Advanced X-Ray Integrated Sources (AXiS) program. Primary funding came from the DOE’s Office of Science.
The new research was just published in the journals Nature and Physical Review Letters.