Helion Hits 150 Million Degrees in Private Fusion First

Helion Shatters Fusion Records with 150 Million Degree Plasma

Helion Energy has announced that its seventh-generation Polaris prototype reactor has reached plasma temperatures of 150 million degrees Celsius, ten times hotter than the core of the sun, while simultaneously demonstrating measurable deuterium-tritium fusion. The dual achievement makes Polaris the first privately developed fusion machine to hit both milestones, marking a significant leap forward for commercial fusion energy.

Breaking Its Own Record

The 150 million degree achievement surpasses Helion's own previous industry record of 100 million degrees Celsius, set by its sixth-generation Trenta prototype. Within the fusion community, 100 million degrees is widely considered the threshold temperature for a commercially viable fusion reactor. The company began operating Polaris at the end of 2024 and in January 2026 became the first private fusion company to use deuterium-tritium fuel after securing regulatory approval to possess and use tritium.

How Polaris Works

Helion's reactor uses a field-reversed configuration design. Fuel is injected at both ends of an hourglass-shaped chamber and converted to plasma. Powerful magnets then accelerate the plasmas toward each other, and upon merging, additional magnets compress the plasma further, raising temperatures to 150 million degrees in less than a millisecond. The company ultimately aims to reach 200 million degrees Celsius for optimal commercial operation.

The Road to Commercial Power

Helion has a landmark power purchase agreement with Microsoft to deliver at least 50 megawatts of fusion-generated electricity by 2028, with Constellation Energy serving as power marketer. Construction is underway on Helion's first commercial plant, Orion, in Malaga, Washington, which broke ground in July 2025. The company, backed by OpenAI CEO Sam Altman as executive chairman, plans to eventually switch from deuterium-tritium to deuterium-helium-3 fuel for commercial operations, which produces more charged particles suited to generating electricity directly from fusion reactions.

Growing Competition

The announcement comes amid intensifying competition in the private fusion sector, with Commonwealth Fusion Systems building its SPARC tokamak demonstration plant and TAE Technologies going public through a merger with Trump Media and Technology Group in a deal valued at six billion dollars.