Scientists at Stanford and SLAC have created a silicon chip that can accelerate electrons using an infrared laser to deliver, in less than a hair’s width, the sort of energy boost that takes microwaves many feet.
Above – This image, magnified 25,000 times, shows a section of an accelerator-on-a-chip. The gray structures focus infrared laser light (shown in yellow and purple) on electrons flowing through the center channel. By packing 1,000 channels onto an inch-sized chip, Stanford researchers hope to accelerate electrons to 94 percent of the speed of light. (Image credit: Courtesy Neil Sapra)
The accelerator-on-a-chip demonstrated in Science is just a prototype, but Vuckovic said its 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.
Science – On-chip integrated laser-driven particle accelerator
This will be for accelerators like taking computers from the mainframe era to the personal computer era.
Accelerator-on-a-chip technology could also lead to new cancer radiation therapies.
Inverted Design
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. But microwaves measure 4 inches from peak to trough, while infrared light has a wavelength one-tenth the width of a human hair. That difference explains why infrared light can accelerate electrons in such short distances compared to microwaves. But this also means that the chip’s physical features must be 100,000 times smaller than the copper structures in a traditional accelerator. This demands a new approach to engineering based on silicon integrated photonics and lithography.
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.
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, made by team members at Stanford.
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. This prototype chip provides only a single stage of acceleration, and the electron flow would have to pass through around 1,000 of these stages to achieve 1MeV. But that’s not as daunting at it may seem, said Vuckovic, because this prototype accelerator-on-a-chip is a fully integrated circuit. That means all of the critical functions needed to create acceleration are built right into the chip, and increasing its capabilities should be reasonably straightforward.
Miniaturizing particle accelerators
Particle accelerators are usually associated with large national facilities. Because photons are able to impart momentum to electrons, there are also efforts to develop laser-based particle accelerators. Sapra et al. developed an integrated particle accelerator using photonic inverse design methods to optimize the interaction between the light and the electrons. They show that an additional kick of around 0.9 kilo–electron volts (keV) can be given to a bunch of 80-keV electrons along just 30 micrometers of a specially designed channel. Such miniaturized dielectric laser accelerators could open up particle physics to a number of scientific disciplines.
Abstract
Particle accelerators represent an indispensable tool in science and industry. However, the size and cost of conventional radio-frequency accelerators limit the utility and reach of this technology. Dielectric laser accelerators (DLAs) provide a compact and cost-effective solution to this problem by driving accelerator nanostructures with visible or near-infrared pulsed lasers, resulting in a 104 reduction of scale. Current implementations of DLAs rely on free-space lasers directly incident on the accelerating structures, limiting the scalability and integrability of this technology. We present an experimental demonstration of a waveguide-integrated DLA that was designed using a photonic inverse-design approach. By comparing the measured electron energy spectra with particle-tracking simulations, we infer a maximum energy gain of 0.915 kilo–electron volts over 30 micrometers, corresponding to an acceleration gradient of 30.5 mega–electron volts per meter. On-chip acceleration provides the possibility for a completely integrated mega–electron volt-scale DLA.
SOURCES- Stanford, Journal Science
Written By Brian Wang, Nextbigfuture.com
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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They mention that
So you’d need some electron gun to create a beam of electrons in the first place, and then many such 0.9 keV sections to get the total beam velocity up to your desired target.
What components would it take to extend this to a complete accelerator on a chip? LED IR laser source, what else?
So a tiny particle accelerator with a lump of plutonium or maybe thorium at the end?
I dunno, I can imagine portable free electron lasers from this emitting a beam of coherent x-rays.
“Above – This image, magnified 25,000 times, shows a section of an accelerator-on-a-chip. The gray structures focus infrared laser light (shown in yellow and purple) “
Magnified X times is a meaningless frase. Why on earth not just have a scale bar?
What the article says they actually achieved is a useful but modest 900 electron-volt acceleration, the rest is extrapolation and the usual hazzah.
In order for that to happen over 30μm, an external femtosecond laser has to be added, and those things are a wee bit larger. Here is one.
I don’t think they are going to be selling ioning radiation “laser” pointers Any time soon on ebay
I have been awaiting this sort of development. I actually for years have thought that a “Mr Fission” if not Back To The Future’s “Mr. Fusion” would be possible by going a full nanometer path. I look forward to further developments.
Short answer: No.
Although it’s getting a high velocity per particle, the flow rate of particles is literally microscopic so you’d have very low absolute power in your thruster. Maybe it could be used as a low power thruster, but at this point we want to know what the efficiency of the system is, and there is no information that this system is more efficient than the existing ion thrusters. Given that power is first transformed into a laser (lots of losses) and then used to accelerate particles (even more losses) I suspect the efficiency is very low. For a particle accelerator used for research that just isn’t a parameter you would prioritise.
Longer answer: It might be used as the basis for developing an ion thruster.
Now that laser accelerator tech is both shown to work and is being made tiny, it could be developed into an ion thruster. As above I can’t see it being anywhere as energy efficient as a more direct electricity -> ion acceleration system, but because it gets such a high velocity it would be more mass efficient. ie. More impulse per kg of propellant, even if it takes more kW.h. So some sorts of deep space missions, especially ones with heaps of power available (to Mercury say) could use this to have their fuel last for many years.
can this teck be used as a powerful ion thruster ?
There is one science fiction franchise where the weapon of choice is
“an unlicensed particle accelerator”.
Ghostbusters.
So this isn’t a particle accelerator on a chip, it’s a component-on-a-chip for a particle accelerator on a desktop.
Pity.
Because if it really WAS a particle-accelerator-on-a-chip then we’d be getting them on ebay or alibaba for $20 delivered to your door in a couple of years. And then nuclear physics in the 2020s would be like the development of software in the 1980s and 90s with literally millions of people mucking around in their spare-rooms/garages/college dorms.
It may be the only way that cheap fusion would ever be discovered soon.
And sure, some idiots would manage to irradiate their genitals or something, but according to the MSM the internet causes genocide and massacres every day because of people writing problematic movie reviews and improper fan fiction, so clearly this might even be safer.
More that it melts the laser cavity. And this is not an weapon, its more like the tricorder of star trek.
Move over Star Trek phaser guns…. the problem with creating laser weapons has always been that if it’s too strong it melts the lense