- At high altitudes and in the vacuum of space, keeping electronics cool can be difficult when air is scarce.
- Scientists from the University of Virginia are investigating ways that plasma, a state of matter usually associated with very hot temperature, could be turned into a kind of freeze ray.
- A new paper details how a helium-based plasma first cools a surface by blasting an ultrathin layer of carbon and water molecules.
When you think of the word “plasma,” extremely high temperatures come to mind. After all, this soup of free electrons (often also as the “fourth state of matter”) is what powers the stars and (hopefully) humanity’s future fusion reactors.
So, it’s surprising that scientists from the University of Virginia are using plasma to create a freeze ray. But this isn’t the armament of choice for some fictional Batman villain—this invention has caught the eyes of the U.S. Air Force.
“You’re in space, which is a vacuum, or you’re in the upper atmosphere, where there’s very little air that can cool,” UVA professor Patrick Hopkins said in a statement. “So what happens is your electronics keep getting hotter and hotter and hotter. And you can’t bring a payload of coolant onboard because that’s going to increase the weight, and you lose efficiency?”
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The Air Force appears to agree, which is why they’ve given $750,000 worth of funding to Hopkins’ (Experiments and Simulations in Thermal Engineering (ExSiTE) Lab. It’s to be used over the next three years to figure out a solution using plasma. But how exactly does plasma—the stuff that makes up the literal Sun—cool down electronics, exactly?
Currently, onboard electronics use cold plates to conduct heat away from sensitive systems. But Hopkins’ says that may not be enough as electronics become more advanced. Although plasma is very hot, it displays a little-known behavior when it strikes a surface—it actually cools down the surface before heating it up. In his experiment, Hopkins and his team fired a purple pulse of plasma through a needle encased in a ceramic insulator before striking a gold plate.
“What I specialize in is doing really, really fast and really, really small measurements of temperature,” Hopkins says in a statement. The results of the experiment were published in the journal ACS Nano in mid-July. “So when we turned on the plasma we could measure temperature immediately where the plasma hit, then we could see how the surface changed. We saw the surface cool first, then it would heat up.”
To understand why this surface first cooled, Hopkins used microscopes and a technique called “time-resolved optical thermometry” to measure thermoreflectance—that is, the measurement of light reflectance based on the temperature on a surface. Hopkins’ team discovered that blasting an ultrathin layer of carbon and water molecules on the plate’s surface is what caused the initial thermal drop.
“There was no information for us to pull from because no prior literature has been able to measure the temperature change with the precision that we have,” Hopkins says. “The plasma rips off the absorbed species, energy is released, and that’s what cools.”
This plasma cooling only lasts a handful of microseconds, but Hopkins imagines that, one day, a robotic arm aboard some far-future spacecraft could quickly zap electronic hot spots and cool them before things get too toasty. But back in the present, the team continues testing other gasses and materials to discover ways of prolonging the cooling effect.
For now, the freeze ray remains locked up in the confines of Arkham Asylum.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.