Plasma sounds like the stuff of science fiction, but you probably encounter the fourth state of matter on a daily basis. Any time you see a neon sign, a fluorescent lightbulb, a flash of lightning, or stare at the sun to feed on its energy, you’re encountering plasma in all its glory.
Plasma is technically an ionized gas, which means that it has a number of properties that make it behave like a cohesive unit, such as being able to conduct electricity and interact with magnetic fields. Plasma is super useful stuff, but it comes with a major downside: like a regular gas, it can be tough to harness without a special container. For human applications, such as a fusion reactor, plasma is usually contained using electromagnetic fields that force the plasma into a desired shape.
But now a team of physicists at Caltech have managed to create a plasma ring in the open air for the first time.
"We were told by some colleagues this wasn't even possible,” Francisco Pereira, a visiting scholar at Caltech, said in a statement. “But we can create a stable ring and maintain it for as long as we want, no vacuum or magnetic field or anything.”
As detailed in a report for the Proceedings of the National Academy of Sciences, Pereira and his colleagues were able to create and sustain plasma rings in open air by aiming a high-powered stream of water at a crystal plate. This stream of water is less than the width of a human hair and hits the plate at the same speed as a bullet.
The crystal plates used in the experiment are able to generate an electrical charge when they encounter friction with other objects (in this case, water). When the high-powered stream of water hits the plate, it creates a smooth, thin layer of positively charged ions as it spreads out over the negatively charged plate.
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At the point where the water hits the plate, this generates a lot of electrons flowing from the plate to the surface where they ionize the gases at the surface. This results in a small, stable plasma ring that is visible under a microscope and can be sustained for as long as the water is flowing across the surface.
It’s unclear what practical applications this discovery will find, although the researchers noted it could find use for energy storage. For now, however, it’s just a pretty visually stunning example of pure science in action.