Fusion startup Helion hits blistering temps as it races toward 2028 deadline

Fusion energy startup Helion said Friday that it has reached a major milestone in its push toward commercial fusion power. The company reported that plasmas inside Polaris, its prototype reactor, have reached 150 million degrees Celsius, about three-quarters of the temperature Helion believes it will ultimately need to operate a commercial fusion power plant." We'ree obviously really excited to be able to get to this place," said David Kirtley, Helion'ss co-founder and CEO.

Helion also said Polaris is operating on deuterated tritium fuel, a blend of two hydrogen isotopes. Kirtley said that makes Helion the first fusion company to run on that fuel mix." "We were able to see the fusion power output increase dramatically as expected in the form of heat," he said.

Based in Everett, Washington, Helion is competing with a growing set of fusion startups that are working to commercialise fusion power, a potentially vast source of clean energy.

That promise has attracted heavy investor interest. This week, Inertia Enterprises announced a $450 million Series A round that included Bessemer and GV. In January, Type One Energy said it was in the process of raising $250 million. Last summer, Commonwealth Fusion Systems raised $863 million from investors including Google and Nvidia. Helion raised $425 million last year from backers including Sam Altman, Mithril, Lightspeed, and SoftBank.

Most fusion startups aim to bring electricity to the grid in the early 2030s. Helion's timeline is tighter. The company has a contract with Microsoft to begin selling its electricity starting in 2028. That power would come from a larger commercial reactor called Orion, which Helion is currently building, not from Polaris.

Every fusion startup sets milestones based on its reactor design. Commonwealth Fusion Systems, for example, needs to heat plasmas to more than 100 million degrees C inside its tokamak — a doughnut-shaped device that uses extremely strong magnets to contain the plasma. Helion's approach is different and requires plasma roughly twice as hot as other companies' systems do to operate as designed.

Helion useswhat'ss known as a field-reversed configuration. The reactor chamber resembles an hourglass. Fuel is injected at the wider ends and converted into plasmas. Magnets then accelerate the plasmas toward one another. When the two plasmas merge, they are initially around 10 million to 20 million degrees C. The merged plasma is then compressed by powerful magnets, raising its temperature to 150 million degrees C. The entire process takes place in less than a millisecond.

Rather than collecting energy from fusion reactions primarily as heat, Helion aims to generate electricity directly using the fusionreaction'ss own magnetic field. Each pulse pushes back against thereactor'ss magnets, inducing an electrical current that can be captured. By pulling electricity straight from the reaction, Helion believes it can operate more efficiently than competitors that rely on converting heat into power.

Kirtley said the company has spent the last year refining some of the reactor's circuits to increasthe amount of electricity recovered.

Although Helion is using deuterium-tritium fuel today, it ultimately plans to transition to deuterium-helium-3. Many fusion startups intend to use deuterium-tritium fuel and extract energy as heat. Helion'ss preferred fuel, deuterium-helium-3, produces more charged particles, which push forcefully against the magnetic fields that confine the plasma. That makes it better suited to Helion's strategy of direct electricity generation. Helion'ss long-term target is to produce plasmas reaching 200 million degrees C — significantly higher than most other companies aim for due to its reactor design and fuel choice." "We believe that at 200 million degrees, that'ss where you get into that optimal sweet spot of where you want to operate a power plant," Kirtley said.

Asked whether Helion has reached scientific breakeven — the point at which a fusion reaction produces more energy than it takes to initiate it — Kirtley declined to answer directly. We focus on the electricity piece, making electricity, rather than the pure scientific milestones.

Helium-3 is common on the moon but scarce on Earth, meaning Helion must create its own fuel. Initially, the company will fuse deuterium nuclei to generate its first batches of helium-3. In normal operation, while the primary power source would come from deuterium-helium-3 fusion, some reactions will still be deuterium-on-deuterium, producing helium-3 that Helion plans to purify and reuse.

Work is already underway to improve and scale the fuel cycle. "It's been a pleasant surprise in that a lot of that technology has been easier to do than maybe we expected", Kirtley said. Helion has been able to produce helium-3" at very high efficiencies in terms of both throughput and purity," he added.

While Helion is currently the only fusion startup planning to use helium-3, Kirtley said he expects others will eventually adopt it as well, suggesting he would be open to selling helium-3 to them. "Other folks, as they come along and recognise that they want to do this approach of direct electricity recovery and see the efficiency gains from it, will want to be using helium-3 fuel as well", he said.

Alongside its work on Polaris, Helion is also building Orion, a 50-megawatt fusion reactor intended to meet the company's Microsoft contract. O  ur ultimate goal is not to build and deliver Polaris," Kirtley said." That'ssss a step along the way towardsa  a scaled power plant."