Private fusion hits three firsts in seven months as ITER keeps building

Helion published its announcement on 14 February 2026. It makes two claims: measurable deuterium-tritium fusion and plasma temperatures of 150 million degrees Celsius (150MºC). The company states Polaris is the first privately developed machine to reach both.

The temperature figure matters because Helion already held the record. Its sixth-generation Trenta prototype reached 100MºC, a threshold the company describes as necessary for commercially relevant fusion. Polaris pushed past that by half again. Helion began operating the seventh-generation Polaris prototype at the end of 2024. In January 2026, it became the first and currently only private fusion machine to use deuterium-tritium fuel, according to the company. Helion also claims it was the first to receive regulatory approval to possess and use tritium for demonstrating fusion energy production.

What Polaris is actually for

Deuterium-tritium is not the fuel Helion plans to sell. The company says it will keep testing Polaris to reach optimal temperatures for deuterium-helium-3 fusion, which it intends for commercial operations. The D-T campaign is a step in the testing program, not the destination.

"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 the company's statement. "We've built and operated seven prototypes, setting and exceeding more ambitious technical and engineering goals each time."

Outside verification came in the same release from people with standing in the field. Ryan McBride, an inertial confinement fusion and pulsed power expert who has worked at Sandia National Laboratories and the University of Michigan, said he had reviewed diagnostic data. "It is exciting to see evidence of D-T fusion and temperatures exceeding 13 keV or 150 million degrees Celsius," he said. Jean Paul Allain, associate director for Fusion Energy Sciences at the Department of Energy's Office of Science, said the Polaris data indicated "strong progress" and noted that getting fusion on the grid requires approaches with rapid turnaround in design and testing. Alan Hoffman, who led early field-reversed configuration work at the University of Washington, said he continues to see the technology scaling.

None of those statements is an independent audit. They are quotes distributed by the company making the claim, which is worth remembering when reading figures that have not been through peer review.

On the commercial side, Helion began building in July 2025 on the site of Orion, its first commercial machine, in Malaga, Washington. The company says that plant will deliver electricity from fusion to the grid for Microsoft.

Realta converts plasma to current, with caveats

Five months later, on 19 June 2026, Realta Fusion said it became the first private fusion company to demonstrate direct energy conversion of plasma kinetic energy into electricity. The work was done with the University of Wisconsin-Madison on the Wisconsin HTS Axisymmetric Mirror prototype, or WHAM.

The converter replaced the center disk on WHAM's end-ring assembly. It slows charged particles leaving the mirror's loss cone using an electrostatic potential, turning their kinetic energy into current. The first prototype has three meshed grids: an electrically grounded grid, an electron repulsion grid and an ion collector grid. During operations, Realta says, the assembly draws multiple amps at around 100 volts, enough for a few lightbulbs.

The company is direct about what this is not. Its own post says the demonstration is "neither a demonstration of net-electricity production nor large-scale conversion of fusion-born power directly into electricity." WHAM runs on deuterium only, so most of the converted energy is input power the company supplied, not fusion power.

Realta's case for direct conversion rests on the physics of magnetic mirrors. The loss cone, a well-known feature of mirror confinement, is normally treated as a confinement problem. Realta argues it is also an exhaust route that keeps the plasma clean and a way to recapture energy from charged particles at higher efficiency than a thermal cycle allows. In a deuterium-tritium plant, the company says 80% of yield arrives as high-energy neutrons and 20% as charged alpha particles.

The plan is to scale the converter to multi-kilowatt and eventually multi-megawatt capability on future devices. Realta says at Qsci = 5 in a D-T plasma, alpha power would match the input power needed to keep the plasma running.

Meanwhile, ITER is still being built

The public project that was supposed to settle these questions is behind schedule and over budget. CNET reported in May 2026 that ITER, the International Thermonuclear Experimental Reactor in southern France, carries an estimated cost of $22 billion and is designed to contain plasma at 150 million degrees Celsius, the same temperature Helion now claims on a far smaller machine.

ITER's timeline slipped by years after cracks were found in the piping of a heat shield in 2020, along with welding distortions and COVID-19 disruptions. CNET put the repair bill at an additional $5 billion. The project's members include more than 30 countries.

"This is a publicly funded project," Javier Artola, a scientist modelling ITER's plasma, told CNET. "It is the knowledge of the world." ITER's chief strategic advisor, Laban Coblentz, framed the collaboration bluntly for the outlet: "That China and Russia were going to collaborate with the US and Europe, and add in Korea, India, and Japan, that's either genius or insane."

Every member state gets access to the science ITER produces, and the project is building a global supply chain along the way. That is the argument for its cost: it de-risks problems private companies would otherwise have to solve alone.

Money keeps arriving

Private capital has not waited. Thea Energy announced on 27 May 2026 that it raised $100 million in Series B funding, led by US Innovative Technology Fund with participation from General Innovation Capital Partners and Linse Capital. The company builds stellarators, a magnetic confinement design it spun out of Princeton University and the Princeton Plasma Physics Laboratory in 2022.

Thea says the money will expand magnet manufacturing, including a second facility in northern New Jersey, and support siting and construction of Eos, a large integrated stellarator. The company also says it is in discussions with over a dozen power offtakers, hyperscalers and utility partners.

The funding round followed Department of Energy certification of Thea's Helios preconceptual design milestone, which the company says made it the first awardee to receive that distinction. Thea claims it built and operated the world's first superconducting magnet array capable of producing the complex fields commercial stellarators need.

All of this sits against a policy backdrop that may shift. The Fusion Report notes that House Science Committee Ranking Member Zoe Lofgren and Subcommittee Chair Jay Obernolte introduced the bipartisan American Leadership in Fusion Act, which would provide $10 billion to commercialize fusion energy, including $3.8 billion for materials and fuel cycle test facilities, $3 billion for a new milestone-based demonstration program and $2 billion for the existing milestone program.

MIT's Nuno Loureiro, director of the Plasma Science and Fusion Center, told MIT Energy Initiative in December 2025 that U.S. government funding for fusion has been largely flat for two decades, hovering around the size of one large private round. "You cannot fund a disruptive technology with non-disruptive levels of money," he said.

Three firsts in seven months is real progress. None of them is a commercial power plant, and the companies announcing them are the ones framing what the results mean.