"We can take power from a plasma," said Realta Fusion co-founder and CEO Kieran Furlong. He called the test a demonstration of "what's possible."
Roughly one-fifth of the energy output from deuterium-tritium fusion reactions consists of charged helium nuclei, also called alpha particles. Realta's direct conversion method captures those charged particles and turns them into electricity on the spot. That electricity can then be recirculated back into the reactor to heat the plasma.
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"You're basically able to recirculate the electricity," Furlong said. "Spinning a flywheel of electricity, if you like, is very beneficial." Furlong estimates that circularity could boost a commercial scale power plant's total output by 20% to 30%.
Realta's achievement builds on decades of fusion research that has sought to harness the energy of the sun. The WHAM device, a magnetic mirror configuration, confines plasma at extreme temperatures. By removing the necessity for steam turbines, heat exchangers, and cooling systems, this method could greatly simplify and lower the expense of future fusion power plants. Realta's next goal is to increase the power output and achieve net positive energy, a milestone that would attract further investment and move fusion closer to commercial reality.
Realta previously raised $36 million in a Series A led by Future Ventures in 2025. The company now plans to raise a new round.
First proposed in the 1950s, magnetic mirror fusion employs magnetic fields to confine plasma in a bottle-shaped configuration. Realta's WHAM device updates this approach with modern superconducting magnets and advanced plasma control, allowing it to achieve the conditions needed for direct conversion. The ability to capture alpha particles directly not only boosts efficiency but also reduces the thermal stress on reactor components, potentially extending their operational lifetime.
Traditional fusion reactor designs rely on steam turbines to convert heat into electricity, but this process caps thermal efficiency at roughly 33%. By capturing the kinetic energy of charged particles directly, Realta's approach skips the thermal cycle entirely, enabling much higher efficiency. This also eliminates the need for massive cooling systems and heat exchangers, potentially reducing the capital cost of a fusion power plant.
Realta is not alone. Helion, another fusion startup backed by Sam Altman, also plans to use direct energy conversion but has yet to demonstrate it publicly. Realta's test makes it the first private company to demonstrate direct energy conversion publicly. "Really helps with the economics," Furlong said.
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