Realta Fusion demonstrates direct electricity extraction from plasma at Wisconsin magnetic mirror device
AI-madeRealta Fusion announced on July 6 that it demonstrated direct energy conversion at the Wisconsin HTS Axisymmetric Mirror (WHAM) device on the University of Wisconsin–Madison campus—pulling electricity from charged plasma particles and using it to power a lightbulb.
The process skips the thermal conversion cycle that most fusion power concepts depend on. Instead of capturing heat, Realta’s system harvests the kinetic energy of charged particles escaping through the magnetic mirror’s loss cone and converts it directly into electricity using an electrostatic approach.
What Realta Fusion achieved
Realta installed a direct energy converter in WHAM’s end-ring assembly on June 19, 2026, and announced results less than two weeks later. That’s a fast turnaround. Chief scientific officer Derek Sutherland described setting up the system as “relatively straightforward.”
The two companies use different fusion concepts and different DEC methods, but both are betting that bypassing or supplementing the thermal cycle is worth pursuing.
The converter relied on an electrostatic approach: three finely meshed grids—an electrically grounded grid, an electron repulsion grid, and an ion collector grid—slowed charged particles as they exited through the loss cone, capturing their kinetic energy and turning it into electricity. The test produced power in the hundreds of watts. Enough to light a bulb.
CEO Kieran Furlong was direct: “We’re the first private fusion company to achieve DEC of plasma kinetic energy into electricity on a real fusion machine.” Sutherland was equally clear about what it doesn’t mean. This isn’t net electricity production, and it’s not large-scale conversion of fusion-born power. It’s a proof of concept—an important one, but still a starting point.
Most of the electricity produced here came from the input power used to heat and sustain the plasma, not from fusion reactions themselves. That ratio would look very different at power plant scale, where fusion-born energy would dominate. The immediate next step is a converter with more coverage and more stages, capable of capturing a larger share of escaping particle energy.
Why magnetic mirrors are suited to direct energy conversion
Not every fusion device works well with DEC. Closed magnetic confinement systems — tokamaks and stellarators — are designed to keep plasma sealed in a loop, which makes tapping escaping particles difficult. Magnetic mirrors are open-ended by design. Charged particles inevitably scatter into what’s called a loss cone and exit the device. Historically, that leakage has been seen as a confinement problem.
Realta sees it differently. Sutherland described the loss cone as “a compelling feature rather than a hurdle.” The escaping particles carry harvestable energy, and the loss cone itself acts as a natural exhaust that helps keep the fusion plasma clean.
WHAM uses high-temperature superconducting magnets to generate a stronger magnetic field, minimizing the size of the loss cone and improving plasma confinement—but not eliminating it entirely. That’s intentional. The particles that do escape are exactly what the DEC system is designed to capture.
Better confinement through stronger magnets, combined with energy recovery from what still leaks out, sits at the core of Realta’s approach. The loss cone stops being a liability and becomes a built-in energy source.
Projected effects on efficiency and cost
DEC won’t replace the thermal cycle in a fusion power plant. Most electricity would still come from capturing neutron energy as heat and running it through a conventional turbine. Sutherland compared the combined system to a hybrid vehicle: “It generates heat to push pistons — or in our case, spin turbines — for most of the power, but with an electric component to improve efficiency.”
Realta projects that DEC can operate at over 90 percent efficiency at power plant scale, though the company isn’t releasing efficiency numbers from this initial test yet. Dedicated measurement campaigns are planned. At full scale, the company believes DEC could generate enough electricity to cover all of the system’s input power requirements for continuous operation—leaving the thermal component entirely available for customers.
Getting there means scaling the DEC system to tens or even hundreds of megawatts. According to Realta, that level of DEC integration could reduce the cost per kilowatt-hour by at least 10 to 20 percent — a meaningful number in a sector where economics are often the deciding factor. DEC also opens up fuel options: Sutherland said the approach could enable catalyzed deuterium-deuterium or deuterium-helium-3 fuels, reducing dependence on tritium breeding, which is a significant logistical and cost challenge for deuterium-tritium fusion power.
Background: DEC’s history and broader industry context
The idea of direct energy conversion isn’t new. Physicist Richard Post at Lawrence Livermore National Laboratory theorized the concept, and it was demonstrated experimentally as far back as the 1970s with the “Venetian blind” converter. What’s changed is who’s doing it and why.
WHAM itself has an interesting origin — it started as a publicly funded collaboration among UW-Madison, MIT, and Commonwealth Fusion Systems. Realta Fusion spun out of that project and now funds most of WHAM’s operations under a public-private partnership structure.
Realta isn’t the only commercial fusion company pursuing DEC. Helion Energy’s magneto-inertial fusion concept is also well-suited to direct conversion, and Helion has discussed using an induction-based DEC method as a core part of its commercial approach. The two companies use different fusion concepts and different DEC methods, but both are betting that bypassing or supplementing the thermal cycle is worth pursuing. At the government level, DARPA launched its Rads to Watts program in 2025, recently funding seven projects focused on directly converting radiation—including potentially neutrons—into electricity. If neutron DEC becomes viable, it could boost efficiency for both fission and fusion systems significantly.
The concept is successful at this scale
Realta’s demonstration at WHAM is a first for a private fusion company: direct energy conversion of plasma kinetic energy into electricity on an operating fusion machine. The test produced hundreds of watts using a three-grid electrostatic converter installed in just under two weeks.
The result confirms the concept works at this scale. It doesn’t demonstrate net electricity production or commercial-scale power conversion. Scaling DEC to megawatt levels — and integrating it with a full deuterium-tritium power plant — remains the longer-term challenge.
If Realta’s efficiency projections hold at scale, DEC could cover the plant’s own power needs and cut electricity costs by 10 to 20 percent, while also expanding the viable fuel options. Those are significant potential advantages—contingent on whether the technology scales as projected.
Kelly is an experienced writer with 15 years of experience exploring the big stories that shape our world, from tech breakthroughs and space exploration to climate, energy, and the fascinating quirks of science. She has a talent for turning complex ideas into sharp, memorable insights that stay with readers long after they’ve finished reading.
