In the US state of Washington, the private company Helion has heated a plasma to 150 million degrees Celsius in its prototype “Polaris,” marking a milestone for private nuclear fusion. This temperature is well above the 100 million degree Celsius mark, considered a crucial threshold for technically viable fusion power plants. At the same time, Helion recorded measurable deuterium-tritium reactions for the first time in a privately funded facility, a finding considered particularly significant due to the high energy density of this fuel. External experts reviewed the diagnostic data and confirmed the temperature measurements as well as the indications of these reactions. The occasion was a recent test run of “Polaris,” which has been operational since the end of 2024. (focus: 18.02.26)
Private companies surpass the 100 million mark – what the leap means
150 million degrees corresponds to approximately 13 kiloelectronvolts, but in practice, more than a record value counts. In the scientific community, the 100 million degree mark is often considered a relevant threshold. Helion already reached this threshold with its predecessor, Trenta, while Polaris now significantly exceeds it.
External verification is crucial, as measurement errors would immediately invalidate the results. According to the company, external experts confirmed both the exceptionally high temperatures and indications of deuterium-tritium (D-T) reactions. Nevertheless, temperature alone is not the deciding factor; stability and repeatability are also crucial.
Deuterium-Tritium Fuel in Private Operation – Approval and Remaining Hurdles
In January 2026, Helion used deuterium-tritium fuel for the first time in a privately funded facility, which is why the project is also under regulatory scrutiny. Tritium is radioactive and subject to strict regulations. Helion reports that it is the first private fusion project to have received the necessary approval.
Ryan McBride, an expert in plasma and pulsed power technology, said after reviewing the data: “It’s exciting to see that there is evidence of deuterium-tritium fusion and temperatures exceeding 13 keV, or 150 million degrees Celsius.” Deuterium-tritium reactions produce a particularly high amount of energy, and government programs also utilize this fuel. For a power plant, however, stable operations and a positive energy balance are paramount.
Rapid Prototypes and the Path to the Grid
Since its founding, Helion has built seven prototypes, with each new plant designed to be built faster than the last. CEO David Kirtley describes the approach this way: “We believe that the surest way to commercialize fusion is to build, learn, and develop as quickly as possible.” This pace facilitates learning, but it also increases the pressure on quality assurance and verification.
A commercial machine is planned to follow “Polaris,” so the next step is already drawing near. In July 2025, construction began in Washington, D.C., on the “Orion” plant. It is intended to feed electricity into the public grid, with Microsoft as a potential customer.
What the private company still needs to prove
In the long term, the private company plans to use deuterium-helium-3, which simultaneously increases the demands. Temperature, stability, and energy yield must be further improved. In addition, the facility must continuously generate more energy than it consumes.
Alan Hoffman, active in fusion research for decades, said: “I continue to see how the technology scales and how energy recovery makes this concept commercially viable.” This sounds optimistic, but proof of its viability in continuous operation remains crucial. Only then will experimental technology become a reliable power source.
Germany: Research, startups, and a multi-billion-euro plan
In Germany, the Max Planck Institute for Plasma Physics in Greifswald is advancing the Wendelstein 7-X stellarator, where stable plasmas and long discharges are being achieved. This is considered an important building block for future continuous operation. At the same time, the private sector is growing, and startups like Proxima Fusion and Marvel Fusion are raising hundreds of millions of euros in investment.
The German government intends to support a fusion action plan, and therefore plans to invest more than two billion euros in research and infrastructure by 2029. However, a grid-connected reactor does not yet exist. Many experts expect large-scale fusion power plants to be operational only in the 2040s or later, while the private company Helion primarily provides an interim technical assessment.