Helion’s Polaris hits 150 million degree plasma milestone toward 2028 grid power

Helion’s Polaris prototype during plasma operations, where 150 million degree Celsius temperatures with D-T fuel mark a private fusion engineering milestone.

(Image courtesy of Helion Energy)

Helion Energy has reached plasma temperatures above 150 million degrees Celsius with its seventh generation Polaris prototype, using a deuterium-tritium fuel mix in its magneto-inertial field-reversed configuration. The result represents a 50% increase over the 100 million degree threshold the company demonstrated with its previous Trenta system.

Polaris employs a pulsed compression approach where fuel plasmas are accelerated and magnetically compressed to ignite fusion conditions. The system uses direct energy recovery, inducing electrical current in the pulsed magnetic coils during plasma expansion rather than relying on steam cycles and turbines. For fusion engineers, this architecture places distinct demands on pulsed power electronics, high-field magnets, and vacuum systems that must cycle thousands of times per day without degradation.

The company now targets higher temperatures with its preferred deuterium-helium-3 fuel cycle, which cuts neutron output versus D-T reactions and eases materials activation challenges. Helion holds the first private fusion license from the Nuclear Regulatory Commission and the first private tritium handling license from the Department of Energy, enabling the D-T testing that informed the Polaris milestone.

With Polaris validating plasma performance, Helion has begun site work for Orion, its first commercial plant under contract to deliver 50 megawatts to Microsoft data centers by 2028. That timeline depends on Polaris confirming not just temperature but pulsed operation rates, energy gain above breakeven, and tritium handling at scale.

The shift to D-He3 reduces tritium breeding requirements but introduces helium-3 supply questions, likely addressed through deuterium-deuterium side reactions or external sourcing. For those tracking component supply chains, Polaris data will show whether pulsed high-field coils can sustain the duty cycles needed for baseload power, and how direct recovery efficiency scales with output. The compact reactor footprint and development pace contrast with longer-cycle tokamak programs, though both paths face distinct integration and materials challenges.

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