Private Fusion Posts Three Firsts in Six Months as ITER Still Waits

The claim comes from Helion's own newsroom, published 13 February 2026. Polaris, the company's seventh-generation prototype, demonstrated measurable deuterium-tritium fusion and hit plasma temperatures of 150 million degrees Celsius. Helion is based in Everett, Washington, and began operating Polaris at the end of 2024.

The company says 100 million degrees Celsius is the threshold plasma temperature for a commercially relevant fusion machine. Its sixth-generation Trenta prototype had already set that mark, so the new figure is a record Helion broke itself. The D-T campaign is one step in a longer test programme. Helion says it will keep raising temperatures in Polaris to reach conditions for deuterium-helium-3 fusion, the fuel it intends to use in commercial operations. That work is expected to continue across the coming test campaigns.

Two outside researchers are quoted in the release. Ryan McBride, who has worked at Sandia National Laboratories and taught nuclear engineering at the University of Michigan, said he reviewed diagnostic data and called the evidence of D-T fusion and temperatures above 13 keV exciting. Alan Hoffman, who led early field-reversed configuration work at the University of Washington, said he continues to see the technology scaling. Both quotes come from the company's announcement, not from independent peer-reviewed publication.

Two more results, both with asterisks

Realta Fusion says it became the first private fusion company to demonstrate direct energy conversion of plasma kinetic energy into electricity, on 19 June 2026, working with the University of Wisconsin-Madison on the WHAM prototype device. The converter sits in place of a centre disk on the end-ring assembly. It slows charged particles leaving the mirror's loss cone with an electrostatic potential, turning their kinetic energy into current. Realta says the single-stage device draws multiple amps at around 100 volts, enough to light a few bulbs.

The company is explicit about the limits. This is not net electricity production and not large-scale conversion of fusion-born power. WHAM is a prototype-scale mirror running on deuterium alone, so most of the converted energy is input power rather than fusion output. Realta says it will scale the converter to multi-kilowatt and eventually multi-megawatt capability on future devices.

Thea Energy's contribution is money and design approval rather than plasma. On 27 May 2026 the Kearny, New Jersey company announced a $100 million Series B led by Thomas Tull's US Innovative Technology Fund, with General Innovation Capital Partners, Linse Capital and a long list of other investors. Thea is commercialising the stellarator, a magnetic confinement design that spun out of Princeton University and the Princeton Plasma Physics Laboratory in 2022.

The funding follows certification by the US Department of Energy of Thea's Helios preconceptual design milestone. The company says that makes it the first awardee to receive the distinction under the DOE's Milestone-Based Fusion Development Program. Thea says it has built and operated a superconducting magnet array capable of producing the complex fields stellarators need, and plans to select a site for its Eos integrated system later this year.

The comparison nobody can avoid

Against that stands ITER, the publicly funded international project in southern France, described by CNET in May 2026 as the world's largest bet on fusion energy. The doughnut-shaped vacuum chamber is designed to hold plasma at 150 million degrees Celsius, the same temperature Helion now claims, but at vastly larger scale and with superconducting magnets kept a few degrees above absolute zero. CNET puts the estimated cost at $22 billion, with an additional $5 billion needed after cracks were found in heat shield piping in 2020, along with welding distortions and pandemic disruption.

The delay matters for how the private results should be read. ITER's purpose is to solve problems once, in public, for more than 30 member states whose researchers get access to the science. As ITER's chief strategic advisor Laban Coblentz told CNET, the project has become a model for how countries of unlike persuasion can work together over decades. Javier Artola, a scientist modelling ITER's plasma behaviour, called it the knowledge of the world.

Private machines can move faster partly because they attempt less. Helion's 150 million degrees was achieved in a device the company describes as a prototype, not a power plant. Realta's converter lit lightbulbs. Thea's milestone is a design certification, not a running reactor.

What is actually proven

Three things can be stated with reasonable confidence. Private fusion companies are now producing data that outside experts are willing to comment on publicly, even if those comments are attached to company press releases. The technical routes differ sharply: Helion's field-reversed configuration, Realta's magnetic mirror, Thea's stellarator, and ITER's tokamak are not variations on one machine.

And the gap between a result and a power plant remains wide. Helion says it began construction in July 2025 at the Orion site in Malaga, Washington, where it intends to deliver electricity from fusion to the grid for Microsoft. Thea is targeting construction of its first Helios plant before the end of the decade and says it is in talks with more than a dozen potential power offtakers.

None of the companies has published a peer-reviewed demonstration of net energy gain. Until one does, the honest summary is that the field has several credible firsts, each narrower than the headline, and a public project in France that is late, over budget and still the reference point everyone measures against.