This Startup’s Creation Is Hotter than the Sun—and It Just Set a Nuclear Fusion Record

A nuclear fusion startup just hit a hot new milestone.

Everett, Washington-based Helion Energy announced that its nuclear fusion prototype reactor achieved plasma temperatures of about 270 million degrees Fahrenheit. To put things in perspective, the temperature they hit is about ten times hotter than the sun’s core, which burns at about 27 million degrees Fahrenheit. The company also announced it was using deuterium and tritium—two isotopes of hydrogen—as fusion fuel, and achieved measurable fusion.

“We believe the surest path to commercializing fusion is building, learning and iterating as quickly as possible,” Helion cofounder and CEO David Kirtley said in a statement. “The historic results from our deuterium-tritium testing campaign on Polaris validate our approach to developing high power fusion and the excellence of our engineering.”

Kirtley also noted Helion has constructed seven prototypes of its reactor. The seventh-generation Polaris, which is the one on which Helion achieved its latest milestones, kicked off operations at the close of 2024. The temperature milestone the prototype achieved broke a previous record set by its sixth-generation Trenta prototype. Trenta had heated plasma to 212 million degrees Fahrenheit, which is considered the threshold temperature for commercial fusion, Helion noted in an announcement. 

Kirtley told TechCrunch that Helion will ultimately need to hit about 392 million degrees Fahrenheit (200 million Celsius) to achieve the “optimal sweet spot” for commercial fusion.

Helion is designing a system that uses nuclear fusion to generate consistent, abundant, and carbon-free energy. Unlike today’s operational nuclear power plants, which rely on nuclear fission—or the process of breaking atoms apart—nuclear fusion generates electricity by combining atoms, much like the way the sun produces energy. Helion heats isotopes into plasma, confines it with magnets, and then compresses it using a strong magnetic field until it gets to extremely hot temperatures. At that point, the isotopes become so hot that they fuse together and release even more energy. The plasma expands during the process, pushing on the electromagnetic field and generating a current that is captured as electricity. Although Helion achieved its milestone with deuterium and tritium fuel, the company ultimately plans to use helium isotope helium-3 as a source of fusion fuel, TechCrunch noted.

Helion is far from the only company pursuing fusion—and pulling in big funding. 

California-based startup Inertia Enterprises raised $450 million in February, Bloomberg reported. Another is TAE Technologies, an almost 30-year-old California-based fusion company that merged with President Donald Trump’s Truth Social in December in a $6 billion deal. Commonwealth Energy Systems, a Massachusetts-based fusion company, raised $863 million in August and teamed up with Nvidia and Siemens in January to accelerate commercialization. And Tennessee-based Type One Energy inked a deal last February to explore plans for developing a commercial nuclear fusion plant with Tennessee Valley Authority on the back of $82.4 million in seed funding. TechCrunch reported that it is in the midst of raising some $250 million more. And just about a year ago Helion itself raised $425 million, bringing its total funding raised to-date to more than $1 billion.

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