150 Million Degrees of Potential: Helion Claims Nuclar Fusion Milestone
Those scientists and venture capitalists experimenting in hopes of controlling and commercializing nuclear fusion have yet to create sustainable or scalable use cases, but one company this week touted its major advancement in demonstrated fusion energy.
Washington state-based Helion reported that its Polaris fusion prototype achieved 150 million degrees Celsius (150MºC) in plasma temperature during tests. Helion says this is the highest ever for a privately developed fusion energy machine, although U.S. national labs and global collaborative projects may have done so.
Nuclear fusion is considered a type of holy grail for energy developers, promising high capacity and low-carbon power generation with almost unlimited potential. All the utility-scale nuclear power plants in commercial operation today utilize nuclear fission reactions, which are splitting atoms to release energy.
A form of nuclear fusion is what powers the sun in our solar system. In manmade experimental testing facilities, most are focused on confining and fusing a plasma using deuterium, tritium and other elements. So far, the National Ignition Facility at Livermore National Lab is one of the few experimental facilities to achieve net energy gain from a fusion reaction.
Helion began operating its 7th-generation Polaris prototype at the end of 2024. In January 2025, it touted itself as the first and currently only private fusion energy machine to use deuterium-tritium (DT) fuel.
“We believe the surest path to commercializing fusion is building, learning and iterating as quickly as possible,” said David Kirtley, co-founder and CEO of Helion, in a statement. “We’ve built and operated seven prototypes, setting and exceeding more ambitious technical and engineering goals each time. The historic results from our deuterium-tritium testing campaign on Polaris validate our approach to developing high power fusion and the excellence of our engineering.”
In achieving plasma temperatures of 150MºC in Polaris, Helion broke its own commercial fusion industry record for plasma temperatures of 100MºC set by its 6th-generation Trenta prototype. Within the fusion industry, 100MºC is considered the threshold plasma temperature for a commercially relevant fusion machine.
Sustaining and controlling that level is the major challenge for fusion developers. Helion says it will continue to increase plasma temperatures in Polaris to demonstrate that it can operate with deuterium-helium-3, which will be relevant for future Helion commercial operations.
Field-reversed configuration (FRC) is a type of fusion device used by Helion. FRC research in the U.S. first began at Los Alamos National Laboratory and was continued at a private company, Math Sciences North West.
Reportedly encouraging results helped researchers and developers move to the construction of the Large S device at the University of Washington under funding from the U.S. Department of Energy, led by Dr. Alan Hoffman, considered an FRC plasmas expert with more than 40 years' experience.
“After reviewing the latest results from the Polaris prototype operating on D-T, I am proud of how far the field has come since the earliest FRC work at UW and Los Alamos,” Hoffman said in a press statement. “I continue to see the technology scaling and Helion’s plasma energy recovery enabling this technology for commercial scale.”
Last summer, Helion started construction on its first plant in Chelan County, Washington. The Orion facility, when completed and commissioned, would supply fusion-generated electricity to Microsoft by 2028, utilizing Constellation Energy as the power marketer.
Another company, Commonwealth Fusion Systems, is developing a project in Chesterfield County, Virginia. Google has committed to a 200-MW offtake agreement with CFS from its first-ever power plant if and when it’s approved and built sometime in the early 2030s.
Google has been a CFS investor since 2021. Helion’s investment backing includes a recent $425 million funding round with participation by Lightspeed, SoftBank, OpenAI founder Sam Altman, Nucor, Mithril Capital and Capricorn Investment Group.
About the Author
Rod Walton, EnergyTech Managing Editor
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Rod Walton has spent 17 years covering the energy industry as a newspaper and trade journalist. He formerly was energy writer and business editor at the Tulsa World. Later, he spent six years covering the electricity power sector for Pennwell and Clarion Events. He joined Endeavor and EnergyTech in November 2021.
Walton earned his Bachelors degree in journalism from the University of Oklahoma. His career stops include the Moore American, Bartlesville Examiner-Enterprise, Wagoner Tribune and Tulsa World.
EnergyTech is focused on the mission critical and large-scale energy users and their sustainability and resiliency goals. These include the commercial and industrial sectors, as well as the military, universities, data centers and microgrids. The C&I sectors together account for close to 30 percent of greenhouse gas emissions in the U.S.
He was named Managing Editor for Microgrid Knowledge and EnergyTech starting July 1, 2023
Many large-scale energy users such as Fortune 500 companies, and mission-critical users such as military bases, universities, healthcare facilities, public safety and data centers, shifting their energy priorities to reach net-zero carbon goals within the coming decades. These include plans for renewable energy power purchase agreements, but also on-site resiliency projects such as microgrids, combined heat and power, rooftop solar, energy storage, digitalization and building efficiency upgrades.