Private fusion posts firsts on three fronts as ITER costs keep climbing

Helion Energy announced on 13 February 2026 that its seventh-generation Polaris prototype became the first privately developed fusion machine to demonstrate measurable deuterium-tritium fusion. It also hit plasma temperatures of 150 million degrees Celsius. The Everett, Washington company said the result broke its own industry record of 100 million degrees Celsius, set by its sixth-generation Trenta device.

Two aspects of that announcement deserve separation. The temperature milestone is a headline figure. The fuel switch matters more. According to the company, Polaris became the first and currently only private fusion machine to use D-T fuel. Helion was also the first company to receive regulatory approval to possess and use tritium for demonstrating fusion energy production. Helion says the D-T campaign is one step in the Polaris testing program, not the destination. Commercial operations are planned around deuterium-helium-3. The company has not said when that campaign will conclude, nor how many shots it has run so far.

"It is exciting to see evidence of D-T fusion and temperatures exceeding 13 keV or 150 million degrees Celsius," said Ryan McBride, an inertial confinement fusion and pulsed power expert, in Helion's release.

Outside voices in the release include Jean Paul Allain, associate director for fusion energy sciences at the Department of Energy's Office of Science, and Alan Hoffman, a veteran of field-reversed configuration research that began at Los Alamos and moved to the University of Washington. None of them provide independent measurements. All are quoted inside a company announcement.

Realta converts plasma energy straight to current

Realta Fusion said it demonstrated direct energy conversion of plasma kinetic energy into electricity on 19 June 2026. The company worked with the University of Wisconsin-Madison on the WHAM prototype device. It describes the converter as a single-stage unit with three meshed grids, a grounded grid, an electron repulsion grid and an ion collector grid. These are installed in place of the center disk on WHAM's end-ring assembly.

The numbers here are modest, and Realta is explicit about that. The assembly drew multiple amps at around 100 volts, enough to illuminate a few lightbulbs. Realta states plainly that this is neither a demonstration of net electricity production nor large-scale conversion of fusion-born power. Because WHAM runs on deuterium only, most of the converted energy came from input power the system supplied, not from fusion reactions. Realta's stated plan is to scale the converter to multi-kilowatt and eventually multi-megawatt capability.

The physics argument is the interesting part. Magnetic mirrors leak. Realta wants to treat that as a feature. Charged particles exiting the loss cone can be slowed by an electrostatic potential and turned into current. This bypasses some of the thermal cycle losses. The company estimates that at a scientific gain of 5 in a D-T plasma, alpha power would equal the input power needed to keep the plasma running.

Thea raises $100m and eyes a site for Eos

Thea Energy announced a $100 million Series B on 27 May 2026. Thomas Tull's US Innovative Technology Fund led the round, with General Innovation Capital Partners, Linse Capital and a longer list of participants. The Kearny, New Jersey company is commercialising the stellarator. This twisted magnetic confinement design was spun out of Princeton University and the Princeton Plasma Physics Laboratory in 2022.

Thea says the money expands magnet manufacturing, including a second facility in northern New Jersey. It also funds siting and construction of Eos, a large integrated stellarator. The company expects to select a site later this year and to double its team. It is in discussions with more than a dozen offtakers, hyperscalers and utilities. It also says it was the first awardee to receive Department of Energy certification of its Helios preconceptual design milestone.

Set against all of this, ITER remains the scale reference. CNET reported on 26 May 2026 that the international project in southern France carries an estimated $22 billion cost. Cracks found in heat shield piping in 2020, plus welding distortions and pandemic disruption, pushed the schedule back by years. These issues added $5 billion in repair costs. Member states number more than 30. ITER's chief strategic advisor, Laban Coblentz, described the collaboration of China, Russia, the US, Europe, Korea, India and Japan as "either genius or insane."

Read together, the two tracks are doing different jobs. ITER is building shared physics and a supply chain in public. The private companies are chasing schedule, and the claims they publish are their own.