Tiny accelerators get electrons up to speed using lasers

accel chip.jpeg
A miniature accelerator chip fits on a 1 euro cent coin. The pictured chip contains 42 different particle accelerators of various lengths. When hit with laser light, an accelerator gives an energy boost to electrons passing through. S. KRAUS AND J. LITZEL/LASERPHYSICS/FAU

By Emily Conover

OCTOBER 18, 2023 AT 11:00 AM

One day, powerful particle accelerators might fit in your pocket.

Two teams of physicists have built tiny structures that both accelerate electrons and keep them confined in a manageable beam, instead of spewing them willy-nilly. That’s a first for such mini accelerators, and a crucial step toward making these devices more useful and widespread.

“One of the main problems with particle accelerators … is that they’re too big and they’re too expensive,” says physicist Jared Maxson of Cornell University, who was not involved with the new research. Miniaturizing the devices means scientists could make high-energy electrons on a tabletop, Maxson says. That could open up new possibilities for medicine and science.

Constructed on silicon chips, the accelerators are composed of two rows of pillars about 2 micrometers tall, reminiscent of miniature rows of skyscrapers. When hit with laser light, the pillar structure generates electromagnetic fields that push the subatomic particles faster and faster along an extremely narrow alley between the pillars, less than a micrometer wide.

Electrons in one device gained 12.3 kiloelectron volts of energy over a distance of half a millimeter, a 43 percent bump that brought the particles to 40.7 kiloelectron volts, physicist Peter Hommelhoff and colleagues report October 18 in Nature.

Meanwhile, carefully placed gaps between the pillars help keep the beam of electrons in focus, mimicking the capabilities of larger accelerators. “This is really the first accelerator based on nanophotonics that contains all the features any modern accelerator contains,“ says Hommelhoff, of the University of Erlangen-Nuremberg in Germany.

Physicist Robert Byer of Stanford University and colleagues reported a similar achievement October 3 at arXiv.org, with energy gains up to 23.7 kiloelectron volts. The two groups are part of a larger collaboration called the Accelerator on a Chip International Program, or ACHIP, which unifies efforts to build these small accelerators.

The world’s most powerful particle accelerator is the Large Hadron Collider, or LHC, near Geneva, with a ring that’s a whopping 27 kilometers around. Protons in the LHC reach energies of trillions of electron volts. The new tiny accelerators, with mere thousands of electron volts, won’t be creating Higgs bosons anytime soon — the particle famously found at the LHC in 2012 (SN: 6/29/22). But such devices have their own set of potential applications.

For example, high-energy electrons can treat skin cancer by damaging the DNA within cancer cells, killing them. But generating the energetic electrons currently requires a roomful of bulky machinery. With an accelerator on a chip, electron beam therapy could become more accessible.

And similar treatments could go more than skin-deep. “The dream is to be able to have a fiber that can go in a human body to do a local radiation treatment … because the whole accelerator can fit inside you,” says Pietro Musumeci of UCLA, who is a member of ACHIP but was not involved with the new results.

Another application could involve using the devices to create special states of light that could be useful for quantum computing. Or the accelerators might be useful for materials research, for example, for making images of thin materials with ultrahigh time resolution.

But the accelerators still have a long way to go. Electrons emerge from the devices at a rate that’s many orders of magnitude below conventional accelerators. And while the devices focus the beam in two dimensions (in the direction of the beam and perpendicular to it horizontally), further work is needed to focus the beam vertically.

The devices’ energy gains still need to be scaled up, too. The energy the electrons accumulate over a given acceleration distance is on par with conventional accelerators, tens of millions of electron volts per meter. But scientists want to far surpass those accelerators with billions of electron volts per meter.
Even so, the work demonstrates techniques that once seemed absurd to attempt. At first, when Byer described the idea to colleagues, “they’d all break out in hilarious laughter,” he says. “We don’t get laughter anymore; we now get appreciation.”
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T. Chlouba et al. Coherent nanophotonic electron accelerator. Nature. Published online October 18, 2023. doi: 10.1038/s41586-023-06602-7.

P. Broaddus et al. Sub-relativistic alternating phase focusing dielectric laser accelerators. arXiv:2310.02434. Submitted October 3, 2023.

See: https://www.sciencenews.org/article/tiny-accelerators-electrons-lasers

Particle accelerators are crucial tools in a wide variety of areas in industry, research and the medical sector. The space these machines require ranges from a few square meters to large research centers. Using lasers to accelerate electrons within a photonic nanostructure constitutes a microscopic alternative with the potential of generating significantly lower costs and making devices considerably less bulky. The latter will open many doors in improved healthcare.
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Researchers at the University of Bristol have developed a method to turn radioactive graphite blocks, a waste product of nuclear reactors, into artificial diamonds that generate electricity. These diamonds produce a small current that could last for thousands of years. Such long-lived "diamond batteries" could be used in spacecraft, implants such as pacemakers, and in other areas where long battery life is crucial.

Nuclear reactors generate heat from highly radioactive uranium rods. The rods are placed in blocks of graphite to control the heat flow and nuclear reactions. After years of absorbing nuclear radiation, the graphite blocks become highly radioactive as well. When nuclear power plants are decommissioned, they have to dispose of the graphite blocks.

The researchers realized they could heat the carbon blocks, which causes the radioactive carbon to turn into a gas. This gas is then collected and compressed to form a diamond. This diamond has some cool properties. Because of its radioactive nature, it can generate a small electric current. This requires no moving parts or maintenance, and can last for thousands of years without needing to be replaced.

The current is too small to power your smartphone, but it could be used for small applications where it is difficult or impossible to replace a battery.

Source: University of Bristol

The announcement by the Western Australian government of an electric vehicle strategy designed to get more EVs on the state’s roads would undoubtedly have put a spring in the step of battery technology enthusiasts.

The $21 million plan will create an infrastructure network running from Perth through to the iron rich territory of the Kimberley, out to the Goldfields hub of Kalgoorlie and beyond to picturesque Esperance coast.

It’s a positive measure mirrored in jurisdictions around the world, as they look to lessen the impact of combustion engines on the environment. A step towards step-change, and one which has the potential to drive significant growth in EV uptake in the years to come.

But here’s a point you may not have considered – where does the electricity used to charge the EVs come from?

That’s the question posed by uranium industry veteran and Valor Resources (ASX:VAL)executive chairman George Bauk when discussing uranium’s place in the EV revolution with Stockhead earlier this week.

Bauk, whose experience in the space spans decades across roles across the world – most recently at CEO and managing director of Northern Minerals – took up the role at Valor earlier this year and quickly picked up a couple of prospective US uranium projects.

He presents as a fan of the EV story, and believes uranium has a globally significant part to play in it.

“There’s no doubting people have bought into the EV message, and that’s a fantastic outcome,” Bauk said.

“But we need to start telling that story of what’s happening upstream, with the primary source of energy. You may charge an EV, but chances are at the moment that the source of power driving your battery is likely to still be a coal power station.

“Renewables will be an excellent positive contributor to our total power generation, but you need baseloads – uranium has the ability to be that clean source of energy underpinning the electric vehicle baseload.”

It’s a compelling case for a commodity blighted by image challenges spanning back to the 1940s, but one with the potential to deliver the clean energy future the world is working towards.

It also means the image issues around uranium are starting to slowly shift, according to Bauk.

“One of the real advantages we have is the pressure being placed on coal,” he said.

“We have a long journey ahead of us in terms of changing the face of uranium, but I think technological advancements, with the smaller systems you can now build, mean you no longer have to develop those major units with the negative views attached.

“People are starting to realise that the contributing factors to past disasters – things like poor maintenance, poor location – aren’t really about the commodity itself.”

Indeed, it’s the Asian powers of China and Russia which are driving growth in nuclear power at the moment, according to the World Nuclear Association – an unfamiliar rhetoric against North America and most of Western Europe in recent times.

The organisation’s numbers show that in September China had 48 operatable reactors up and running, 12 under construction, and 44 more planned. India’s comparative numbers were 22, seven and 14.

These numbers in growth economies are surely nothing to be sneezed at.

But what about pricing? Uranium bulls have long trumpeted the potential for the commodity’s price to soar – having peaked above US$100 per pound in 2007, spot prices currently sit around the US$30/lb mark.

Bauk believes uranium prices will improve – “they just have to” – but said his preference would be for a steady increase rather than a price spike.

“Spikes in any commodity, I think, create long-term pain in exchange for short-term equity gain,” he said.

The latest step in Bauk’s uranium journey is the recent acquisition of by Valor of the Hook Lake and Cluff Lake uranium projects in Saskatchewan’s highly prospective Athabasca Basin.

The region has historically produced around 20% of the world’s primary uranium supply and has been the site of 18 major uranium deposits since 1968.

A total of 10 of the world’s top 15 highest-grade uranium mines operate in the basin.

Fair to say Valor has bought into some fertile territory. For Bauk, locale is the most exciting aspect of the company’s emerging uranium narrative.

“When you really stand back and have a look at uranium prospectivity across the world, the point of reference is most often the Athabasca Basin,” he said.

“The amount of time people talk about the Athabasca Basin, about deposits similar in style to the Athabasca Basin in geological settings around the world – it sets the standard, and it hosts the world’s highest grade deposits.”

Valor Uranium
Uranium enriched surficial mineralisation at Hook Lake. Pic: Company supplied
Operating in a jurisdiction renowned for uranium is a significant plus, but Valor’s other advantage is the presence of non-executive director and career geologist Gary Billingsley on the ground at his home in Saskatoon.

“With COVID-19, and the inability to travel like we once did at the moment, it makes it much easier to have a board member physically living in the province where our project is,” Bauk said.

“He’s a geologist by qualification and has worked with uranium before – he’s got a great relationship with us and knows most the uranium geologists in Saskatchewan.

“It’s a factor which allows us a presence on the ground, and to maintain the momentum without having to worry about concerns around remote control through COVID-19.”

The transaction for Valor’s Canadian uranium projects is close to shareholder signoff, and the company plans to hit the new year running with a ground-based geophysics program.

“We’ve got some great things to follow up,” Bauk said.

“Hook Lake has some amazing rock chip samples, and there are mines nearby which have produced uranium at nearly 1% – those are extraordinary grades.

“We want to get out on the ground and start working it up, from drill targets to drilling as soon as possible.”

With shifting appetites and changing perceptions shaping uranium’s future, VAL appears well placed to capitalise in 2021 and beyond.

See: https://stockhead.com.au/resources/why-uranium-has-a-central-place-in-an-electric-vehicle-future/

The long-lasting miniaturized power sources that can supply energy continually to power handheld gadgets, sensors, electronic devices, unmanned airborne vehicles in space and extreme mining are some of the examples where this is an acute need. It is known from basic physics that radioactive materials decay over years and some nuclear materials have a half-life measured in thousands of years. The past five decades of research have been spent harnessing the decay energy of the radioactive materials in order to develop batteries that can last until the radioactive reaction continues. Thus, an emergent opportunity of industrial symbiosis to make use of nuclear waste by using radioactive waste as raw material to develop batteries with long shelf life presents a great opportunity for sustainable energy resource development. However, the current canon of research on this topic is scarce and the arena of research is limited.
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