Particle accelerator fits in a silicon chip

Particle accelerator fits in a silicon chip

Technology News |
By Nick Flaherty

The team at Stanford University and the SLAC particle accelerator, backed by the Gordon and Betty Moore Foundation set up by one of the founders of Intel, and the European Union’s  Horizon 2020 Research and Innovation Programme, used infrared lasers and a nanoscale silicon channel to build the accelerator. The infrared pulses are synchrnised to boost the energy of the electrons. 

Details of the protoype accelerator-on-a-chip were published in today’s issue of Science. The key is the design and fabrication techniques can be scaled up to deliver particle beams accelerated enough to perform cutting-edge experiments in chemistry, materials science and biological discovery that don’t require the power of a massive accelerator, says Prof Jelena Vuckovic at Stanford.

“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,” she said. “We want to miniaturize accelerator technology in a way that makes it a more accessible research tool.”

“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,” said Robert Byer, who leads the Accelerator on a Chip International Program, or ACHIP, a broader effort of which this current research is a part.

In a traditional accelerator, like the one at SLAC, engineers generally draft a basic design, then run simulations to physically arrange the microwave bursts to deliver the greatest possible acceleration. For the chip accelerator, Vuckovic’s team solved the problem using inverse design algorithms that her lab has developed. These algorithms allowed the researchers to work backward, by specifying how much light energy they wanted the chip to deliver, and tasking the software with suggesting how to build the right nanoscale structures required to bring the photons into proper contact with the flow of electrons.

“Sometimes, inverse designs can produce solutions that a human engineer might not have thought of,” said R. Joel England, a SLAC staff scientist and co-author on the Science paper.

The design algorithm came up with a chip layout of nanoscale mesas, separated by a channel, etched out of silicon. Silicon wires, poking through the channel wall at strategic locations direct the laser pulses onto a group of electronics.

The researchers want to accelerate electrons to 94 percent of the speed of light, or 1 million electron volts (1MeV), to create a particle flow powerful enough for research or medical purposes. The prototype chip provides a single stage of acceleration, and the electron flow would have to pass through around 1,000 of these stages to achieve 1MeV. This is possible on a single chip, says Vuckovic.

The researchers are designing a chip with 1000 stages for the end of 2020 to reach the 1MeV target.

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