“Algorithms allowed the researchers to work backward”
Using an inverted design model, Stanford researchers have flipped the script when it comes to particle accelerators, creating a tiny particle accelerator that fits onto a chip.
The invention could herald a new form of miniaturised technology that changes how experiments are conducted in material sciences and increases surgical accuracy.
The basic idea of an accelerator is that you continually hit a particle with radio waves so it moves a bit faster after each hit. The world’s faster accelerator, Stanford Linear Accelerator, can make particles reach 99 percent of the speed of light.
Researchers use accelerators to crash particles together at high speeds to better understand the physical laws that govern matter and energy.
In industrial settings particle accelerators are used in the manufacturing of semiconductors and in the medical sector for patient radiation therapy, they are even used in the creation of shrink wrap plastic.
Standard thought on particle accelerators is often that bigger is better: the Large Hadron Collider built by the European Organization for Nuclear Research (CERN) is located in a 17-mile circular tunnel buried over 500 feet under France and Switzerland.
As Stanford Professor Jelena Vuckovic commented on her research: “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. We want to miniaturize accelerator technology in a way that makes it a more accessible research tool.”
But in today’s issue of Science, Vuckovic explains how her team carved a nanoscale channel out of silicon, “sealed it in a vacuum and sent electrons through this cavity while pulses of infrared light – to which silicon is as transparent as glass is to visible light – were transmitted by the channel walls to speed the electrons along.”
Algorithmic Design Process
The team used white infrared light, which passes through silicon, to hit and push the particles up to speed as it moves though the nanoscale channel.
The Stanford team used an inverse design process to work backwards and create an accelerator that was on the nanoscale. They did this using algorithms that identified the optimum way in which particles could be accelerated along a silicon channel.
The researchers note that: “The design algorithm came up with a chip layout that seems almost otherworldly. Imagine nanoscale mesas, separated by a channel, etched out of silicon. Electrons flowing through the channel run a gantlet of silicon wires, poking through the canyon wall at strategic locations. Each time the laser pulses – which it does 100,000 times a second – a burst of photons hits a bunch of electrons, accelerating them forward. All of this occurs in less than a hair’s width, on the surface of a vacuum-sealed silicon chip.”
The chips designed by the Stanford team could have significant medical applications when it comes to treating cancer as current radiation therapy treatments often work like a shotgun as energised elections hit not just the targeted tumour; but also the patient’s skin causing burn damage to the cells. In future radiation therapy, using a modified chip-sized accelerator placed under skin near the tumour could simply target just the cancerous area with precision.
While the Stanford Chip-Sized Particle accelerator is just a prototype the team expect to get particles up to 94 percent of the speed of light by linking together an array of the nanoscale chips.