When most of us think of particle accelerators, we think of massive feats of engineering like CERN’s Large Hadron Collider, which remains the largest machine in the world. But now, a team of researchers from Stanford University and the SLAC National Accelerator Laboratory have achieved a feat of engineering on the opposite end of the spectrum: they’ve built a particle accelerate that fits on a single computer chip.
“The largest accelerators are like powerful telescopes. There are only a few in the world and scientists must come to places like SLAC to use them,” said Jelena Vuckovic, a professor at Stanford and the electrical engineer who led the project. “We want to miniaturize accelerator technology in a way that makes it a more accessible research tool.”
Designing a large particle accelerator typically begins with a basic design, followed by simulations to help the designers arrange the microwave bursts for maximum acceleration – but since the necessary light sources were orders of magnitude smaller than a microwave, a different approach was necessary. The team instead used inverse design algorithms, allowing the team to specify the desired light energy first and then allowing the simulation software to suggest the appropriate nanoscale structures. “Sometimes, inverse designs can produce solutions that a human engineer might not have thought of,” said co-author R. Joel England.
While not as powerful as its gargantuan siblings, the tiny particle accelerator developed by the research team is able to accelerate electrons using an infrared laser. To build the particle accelerator prototype, the team created a nanoscale silicon channel, vacuum-sealed it, inserted electrons, and used the infrared laser (which can pass through silicon) to accelerate those electrons.
While just a prototype, Vukovic is confident that the techniques used to build it could be scaled up, potentially aiding new experiments and capabilities in chemistry, biology and other fields that wouldn’t otherwise be feasible. Co-author Robert Byer, for instance, suggested that miniaturized accelerator technology could be used for cancer treatments as a more focused alternative to medical x-rays. “In this paper we begin to show how it might be possible to deliver electron beam radiation directly to a tumor, leaving healthy tissue unaffected,” he said.
About the research
The research described in this article was published in Science Vol. 367, Issue 6473 as “On-chip integrated laser-driven particle accelerator.” The paper, which can be accessed here, was written by Neil V. Sapra, Ki Youl Yang, Dries Vercruysse, Kenneth J. Leedle, Dylan S. Black, R. Joel England, Logan Su, Rahul Trivedi, Yu Miao, Olav Solgaard, Robert L. Byer and Jelena Vučković.
Header image: A 25,000x magnification of the chip-based accelerator. Image courtesy of Neil Sapra via Stanford University.