Lead: On Feb. 13, 2026, Everett, Washington–based Helion Energy said its Polaris prototype reached peak plasma temperatures of 150 million degrees Celsius, a milestone the company calls about three-quarters of the way toward its commercial target. The firm is running Polaris on deuterium–tritium fuel and reports a clear rise in fusion output during experiments. Helion aims to deploy a larger 50-megawatt machine, Orion, to meet a contract to sell electricity to Microsoft beginning in 2028. Company leaders say the work advances their direct-electrical-recovery design, though independent verification of some claims is pending.
Key Takeaways
- Polaris reached 150 million °C during pulses, which Helion describes as roughly 75% of the temperature it expects to need for commercial operation.
- Helion is testing Polaris with deuterium–tritium (D–T) fuel and reported a substantial rise in fusion power output measured as heat during those runs.
- The company targets 200 million °C as its optimal operational point for scaled power plants, higher than many tokamak-based competitors.
- Helion plans to sell electricity to Microsoft starting in 2028 from its 50 MW Orion reactor, not from Polaris.
- Helion raised $425 million in 2025 from investors including Sam Altman, Mithril, Lightspeed, and SoftBank; other fusion financing cited this week includes a $450 million Series A for Inertia Enterprises and Commonwealth Fusion Systems’ $863 million raise.
- Helion’s field-reversed configuration compresses merged plasmas in under a millisecond, initially merging at ~10–20 million °C before magnetic compression to 150 million °C.
- The company plans to move toward deuterium–helium-3 fuel over time; helium-3 is scarce on Earth and will be at least partially bred in situ.
Background
Fusion startups use several different technical routes to reach net energy and, eventually, grid-scale power. Many firms focus on tokamaks—doughnut-shaped chambers that confine plasma with strong magnetic fields—and commonly cite 100 million °C as a key temperature benchmark. Helion uses a different geometry, a field-reversed configuration (FRC), and designs its systems around direct electrical extraction from fusion pulses rather than relying primarily on thermal cycles.
Investor interest in fusion has surged as firms report incremental technical milestones. In 2025 and early 2026 multiple startups announced large funding rounds, reflecting both optimism and competition in the sector. Alongside private capital, offtake contracts and corporate partners (for example, Microsoft’s agreement with Helion) have become a way for companies to set commercial timetables that are more aggressive than traditional utility planning.
Main Event
Helion reported that Polaris plasmas reached 150 million °C during recent pulses. The company said pulses begin with two plasma streams injected at the chamber ends, which merge at roughly 10–20 million °C; strong magnets then compress the merged plasma to the peak temperature in less than a millisecond. Helion characterizes the 150 million °C result as a major step toward its 200 million °C goal for sustained, economical power production.
For these runs Helion used deuterium–tritium fuel, and company engineers observed a sharp increase in fusion-produced heat as expected from D–T reactions. Helion’s CEO and co-founder, David Kirtley, framed the milestone in terms of the company’s strategy: improving circuit recovery to harvest electricity directly from the fusion pulse’s changing magnetic fields rather than converting heat through turbines.
Helion emphasized that Polaris is a development-stage machine; the contract with Microsoft anticipates electricity deliveries beginning in 2028 from Orion, a larger 50 MW reactor the company is building. Polaris is therefore a stepping-stone: a platform to refine plasma compression, fuel handling and direct energy recovery circuitry ahead of scaled units.
Analysis & Implications
Technically, Helion’s FRC approach requires hotter plasmas than many tokamak designs because the system relies on higher-energy ions and charged-particle production suited to direct electrical extraction. That drives the company’s 200 million °C target, which it frames as an operational “sweet spot” for power-plant efficiency. Reaching 150 million °C is significant, but temperature alone does not equal energy breakeven or a commercial metric such as net electrical output per pulse.
Helion’s focus on direct electrical recovery could provide efficiency advantages if the company can reliably capture and condition the pulsed current at utility scale. Bypassing a steam turbine reduces plant complexity and potentially improves round-trip energy conversion, but it also introduces new engineering challenges: pulse-to-pulse consistency, high-voltage insulation in a fusion environment, and long-term component durability.
Commercial timelines matter because Helion has publicly committed to a Microsoft supply beginning in 2028 and is competing with firms targeting early- to mid-2030s grid entry. If Helion keeps its schedule, it will face not only technical milestones but also regulatory approvals, grid interconnection work, and supply-chain scaling for specialized components and fuels like helium-3.
Comparison & Data
| Company / Design | Noted temperature target (°C) | Fuel | Delivery model |
|---|---|---|---|
| Helion (FRC) | 150 observed; 200 target | D–T now; D–He-3 planned | Direct electricity per pulse; Orion 50 MW for Microsoft (2028) |
| Commonwealth Fusion Systems (tokamak) | ~100+ | D–T | Thermal conversion (tokamak path) |
| Typical tokamak benchmark | ~100 | D–T | Turbine/heat cycle |
The table contextualizes Helion’s temperature goals against common tokamak targets and a leading competitor. Helion’s higher nominal temperature reflects both its FRC geometry and its planned shift to deuterium–helium-3 fuel, which produces a larger fraction of charged particles—an attribute Helion says supports direct electrical conversion.
Reactions & Quotes
Helion leadership presented the temperature milestone as validation of both plasma physics choices and recent engineering improvements to energy-recovery circuits. The company also stressed that Polaris is an experimental machine on the path to Orion.
“We’re obviously really excited to be able to get to this place.”
David Kirtley, Helion co-founder & CEO
Kirtley emphasized iterative progress: refining circuits to increase recovered electricity and using Polaris data to de-risk Orion’s design. He described the D–T runs as confirming expected rises in fusion output and said the team is moving to higher temperatures and fuel cycles.
“We were able to see the fusion power output increase dramatically as expected in the form of heat.”
David Kirtley, Helion co-founder & CEO
The company also positioned its fuel strategy as forward-looking: starting with D–T for early tests, then shifting to D–He-3 for commercial runs because of the greater proportion of charged products the fuel produces, which fit Helion’s direct-electrical approach.
“We believe that at 200 million degrees, that’s where you get into that optimal sweet spot of where you want to operate a power plant.”
David Kirtley, Helion co-founder & CEO
Unconfirmed
- Independent confirmation of the 150 million °C measurement and the exact duration and energy content of pulses has not been published in peer-reviewed literature.
- Helion’s claim to be the first fusion company to operate Polaris on D–T fuel is a company statement and has not been independently verified against all laboratory programs worldwide.
- Company statements about high-efficiency helium-3 production are internal results; external validation and full operational metrics remain to be published.
Bottom Line
Helion’s report that Polaris reached 150 million °C is an important development for that company’s FRC pathway and its plan to extract electricity directly from fusion pulses. The milestone advances Helion toward its 200 million °C target and its commercial promise to deliver power via Orion in 2028, but temperature milestones alone do not equate to scientific breakeven or a commercially viable, continuous power plant.
Key near-term questions remain: independent verification of performance metrics, durability and conditioning of power-extraction systems over many pulses, regulatory and grid-integration steps for a novel generator, and practical production or sourcing of helium-3 at scale. Investors and industrial partners will be watching whether Helion translates laboratory milestones into reproducible, utility-ready electricity deliveries on the company’s accelerated schedule.