Four Fusion Results in Four Months: What the Private Sector Has Actually Shown

Helion Energy says its seventh-generation Polaris prototype is the first privately developed fusion machine to demonstrate measurable deuterium-tritium (D-T) fusion. The company also says the machine reached plasma temperatures of 150 million degrees Celsius. Both milestones appeared in a newsroom post dated 13 February 2026.

The temperature figure matters because it breaks Helion's own record. The company says its sixth-generation Trenta machine had previously reached 100 million degrees Celsius, the level the fusion industry generally treats as the threshold for a commercially relevant machine. Polaris began operating at the end of 2024, and Helion says it started running on D-T fuel in January 2026, the first private machine to do so.

Helion's chief executive, David Kirtley, framed the results as a byproduct of iteration rather than a single breakthrough. "We've built and operated seven prototypes, setting and exceeding more ambitious technical and engineering goals each time," he said in the announcement. The company also notes it was the first to receive regulatory approval to possess and use tritium for demonstrating fusion energy production.

What the D-T milestone does and does not mean

D-T is not Helion's commercial fuel. The company says it will keep testing Polaris to reach optimal temperatures for deuterium-helium-3 fusion, the mix it intends to use in commercial operations. The D-T campaign is a step in a testing programme, not the end of it.

The results drew comment from people outside the company. Ryan McBride, an inertial confinement fusion and pulsed power specialist 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, adding that he looked forward to further progress. 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." He added that fusion on the grid requires approaches that enable rapid turnaround in design and testing.

Helion is also building. In July 2025 the company began construction on the site of Orion, its first commercial machine, in Malaga, Washington. Helion says Orion will deliver electricity from fusion to the grid for Microsoft.

"I am impressed with our nation's ingenuity and the pace at which we are de-risking our path to fusion commercialization." Jean Paul Allain, DOE Office of Science

Three other results, three other approaches

Thea Energy announced on 27 May 2026 that it had raised $100 million in Series B funding, led by Thomas Tull's US Innovative Technology Fund, with General Innovation Capital Partners and Linse Capital participating. The Kearny, New Jersey company is commercialising a stellarator design, a magnetic confinement architecture it spun out of Princeton University and 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-scale integrated stellarator.

Thea also claims two technical firsts. It says it built and operated the world's first superconducting magnet array capable of producing the complex magnetic fields commercial stellarators need. It also says its full-scale planar shaping magnets, destined for Eos, have been de-risked. Gaetano Crupi of USIT argued the architecture shifts complexity "from precision mechanical fabrication to software-defined controls." The company says it is in discussions with more than a dozen power offtakers, hyperscalers and utility partners.

Realta Fusion went in a different direction entirely. On 19 June 2026, working with the University of Wisconsin-Madison on the Wisconsin HTS Axisymmetric Mirror device, the company demonstrated direct energy conversion of plasma kinetic energy into electricity. Realta describes this as a first for a commercial fusion company.

The principle is not new, but the demonstration is. A single-stage converter with three meshed grids, fitted to WHAM's end-ring assembly in place of the centre disk, slows charged particles leaving the mirror's loss cone and converts their kinetic energy into current. Realta says the assembly draws multiple amps at around 100 volts, enough to light a few bulbs.

Its own post is unusually candid about the limits. Realta states plainly that this is neither a demonstration of net electricity production nor large-scale conversion of fusion-born power. It also notes that WHAM runs on deuterium only, so most of the converted energy comes from input power rather than fusion. The company's stated plan is to scale to multi-kilowatt and eventually multi-megawatt capability. For a first-generation D-T plant, it estimates 80 percent of yield arrives as neutrons and 20 percent as charged alpha particles, the portion its converter could in principle capture.

The public project in the background

These private results sit alongside ITER, the publicly funded international project in southern France. CNET reported in May 2026 that the machine, a doughnut-shaped vacuum chamber designed to contain plasma ten times hotter than the Sun's core, carries an estimated cost of $22 billion. Its 150-million-degree plasma will be held by superconducting magnets kept a few degrees above absolute zero.

ITER's timeline slipped by years after cracks were found in heat shield piping in 2020, alongside welding distortions and COVID-19 disruption, with an additional $5 billion needed for repairs, according to CNET. The project's chief strategic advisor, Laban Coblentz, described the collaboration between China, Russia, the US, Europe, Korea, India and Japan as "either genius or insane." Javier Artola, a scientist modelling ITER's plasma, put the counter-argument for openness: "This is a publicly funded project. It is the knowledge of the world."

That is the useful context for the private announcements. Each company reports its own milestones, on its own schedule, with its own definitions of success. Helion's 150 million degrees came with a fuel it will not use commercially. Realta's converter produced amps, not net power. Thea's funding followed a DOE preconceptual design certification, not a working plant.

None of that makes the results meaningless. It makes them partial. The pattern across February, May, June and July 2026 is a field reporting progress in pieces, one subsystem at a time, while the machine that would prove the whole thing remains unbuilt.