Crystal device could be used to build tiny particle accelerators

Chip-sized devices can produce very intense light, which could help build miniature X-ray machines and particle accelerators

To Carmela Padavich-Callaghan

Micrometer-sized devices that produce light by firing electron beams onto crystalline slabs could be used to build microparticle accelerators and X-ray machines. Such chip-sized devices can be manufactured faster, cheaper and more compact than current particle accelerators.

The new device, built by Yi Yang at the University of Hong Kong and colleagues at the Massachusetts Institute of Technology, consists of a special piece of silicon called a photonic crystal, a modified scanning electron microscope that shoots an electron beam onto it, and the emitted light. Devices that detect This setup takes advantage of the electromagnetic field that surrounds the electrons as they move, and can excite charged particles in nearby materials, in this case photonic crystals, to emit light.

From mathematical models, the researchers knew that the interaction between the crystal and electrons could be enhanced by adding patterns to the former, so they etched into it a grid of circular depressions, each about 100 nanometers wide. . Normally, light and electrons do not interact much, but by designing the energy and momentum of light to match the energy and momentum of electrons, an unusually large interaction between the two is possible. This matching method can ultimately boost luminescence by up to a million times, says Yang.

That light has many potential uses, from spectroscopy, where it helps scientists learn about the internal structure of various materials, to light-based communications.

Peter Hommelhoff of the University of Erlangen-Nuremberg in Germany, in particular, says that it can be used to create small particle accelerators. Instead of bombarding the particles with more common microwaves, researchers can use powerful light pulses to accelerate them, he says.

Thomas Krauss of the University of York, UK, says the new device could be a step not only for tiny particle accelerators, but also for smaller X-ray machines. X-rays are basically waves of light with wavelengths too short to be seen. By matching the silicon patterns and electron velocities in the device, it may be possible to change the wavelength of the emitted light to X-rays.

“When you have a doctor take an x-ray, it’s a big beast of a machine. Now you can imagine doing it with a small light source on a chip,” he says. It could make X-ray technology more accessible to medical facilities and portable for use by emergency first responders.