Helion's Polaris Hits 150 Million Degrees, First Private D-T Fusion

Helion Energy, based in Everett, Washington, said its seventh-generation Polaris device hit both milestones during a testing campaign that began at the end of 2024. The company announced the results in a newsroom post dated 13 February 2026 and called them industry firsts.

The deuterium-tritium work is the more consequential of the two. According to the company, Polaris became the first and currently only private fusion machine to run on D-T fuel, which produces high-energy neutrons alongside charged alpha particles. Helion says it was also the first company to receive regulatory approval to possess and use tritium for demonstrating fusion energy production.

The temperature figure is a step up from the company's own previous record. Helion's sixth-generation Trenta prototype reached 100 million degrees Celsius, a level the fusion industry generally treats as the threshold for a commercially relevant machine. Polaris went to 150 million degrees Celsius, or roughly 13 keV, according to Ryan McBride, an inertial confinement fusion and pulsed power specialist who reviewed diagnostic data from the campaign.

"It is exciting to see evidence of D-T fusion and temperatures exceeding 13 keV or 150 million degrees Celsius, and I look forward to seeing more progress," McBride said.

Helion's chief executive framed the results as the product of iteration rather than a single breakthrough. "We believe the surest path to commercializing fusion is building, learning and iterating as quickly as possible," said David Kirtley, co-founder and CEO. "We've built and operated seven prototypes, setting and exceeding more ambitious technical and engineering goals each time."

The company is not treating D-T as its end state. Helion says it will keep raising plasma temperatures in Polaris to reach conditions for deuterium-helium-3 fusion, the fuel mix it intends to use in commercial operations. That reaction is harder to ignite than D-T, and the switch is central to Helion's claim that its plants can avoid the neutron flux that drives activation and shielding requirements in conventional fusion designs.

Outside voices in the release were positive but measured. Jean Paul Allain, associate director for fusion energy sciences at the Department of Energy's Office of Science, said the data indicated strong progress and that getting fusion onto the grid requires approaches that allow rapid turnaround in design and testing. Alan Hoffman, who led early field-reversed configuration work at the University of Washington and has spent more than four decades on fusion devices, said he continues to see the technology scaling and pointed to Helion's plasma energy recovery as the enabler for commercial scale.

None of these statements amount to a claim of net energy gain, and Helion did not present one. A measurable D-T reaction and a temperature reading are diagnostic results, not a power plant. The company's own release says the D-T result is one step in the Polaris testing program.

What is actually being built

The commercial timeline rests on a separate track. Helion began construction in July 2025 at the site of Orion, its first commercial machine, in Malaga, Washington. The company says Orion will deliver electricity from fusion to the grid for Microsoft. That is the deliverable that will be judged, and it depends on fuels and operating regimes Polaris has not yet demonstrated.

Helion's approach is unusual among fusion firms in promising electricity rather than heat as the product. The company's materials describe low-cost, carbon-free power from fusion, a claim that remains unproven at any scale by any private developer.

The broader field is moving on several fronts at once. ITER, the publicly funded international tokamak under construction in southern France, carries an estimated cost of $22 billion, according to CNET, and is designed to contain plasma at 150 million degrees Celsius, the same figure Helion reported for Polaris. ITER's schedule slipped by years after cracks were found in heat shield piping in 2020, along with welding distortions and pandemic disruption, requiring an additional $5 billion for repairs.

ITER's chief strategic advisor, Laban Coblentz, told CNET that the project's cross-bloc membership, spanning China, Russia, the US, Europe, Korea, India and Japan, is either genius or insane. Javier Artola, a scientist modelling ITER's plasma behaviour, described the project as publicly funded knowledge belonging to the world. Every problem ITER solves is one fewer for private companies, the argument goes, even as those companies try to beat it to milestones.

Private capital keeps flowing. Thea Energy, a stellarator developer spun out of Princeton University and the Princeton Plasma Physics Laboratory in 2022, said on 27 May 2026 that it raised $100 million in Series B funding led by Thomas Tull's US Innovative Technology Fund. The company says the round will expand magnet manufacturing, including a second facility in northern New Jersey, and support siting and construction of Eos, a large integrated stellarator. Thea says it is in discussions with more than a dozen power offtakers, hyperscalers and utilities, and aims to start construction on its first Helios power plant before the end of the decade.

Realta Fusion reported a different kind of first. On 19 June 2026, working with the University of Wisconsin-Madison on the WHAM mirror device, the company demonstrated direct energy conversion of plasma kinetic energy into electricity, which it describes as the first such demonstration by a commercial fusion company. The single-stage converter uses three meshed grids and drew multiple amps at around 100 volts, enough to illuminate a few lightbulbs. Realta was explicit that this is not net electricity production.

That caution is worth holding onto across the sector. A temperature record, a fuel first, a converter drawing a few amps: each is a real data point on a long path, and none of them is a working power plant.