Fusion startup Helion reaches scorching temperatures as it races toward 2028 deadline

Everett, Washington-based fusion energy startup Helion announced Friday that it has reached a milestone in its quest for fusion energy. The plasma inside the Polaris company’s prototype reactor has reached 150 million degrees Celsius, which is three-quarters of the way to what the company thinks it will need to operate a power plant.

“We’re obviously very excited to be able to get to this point,” David Kirtley, founder and CEO of Helion, told TechCrunch.

Polaris also runs on deuterium-tritium fuel – a mixture of two isotopes of hydrogen – which Kirtley said makes Helion the first fusion company to do so. “We were able to see the fusion power increase significantly as expected with the temperature setting,” he said.

The startup is locked in a race with several other companies that want to sell fusion power, which could be an unlimited source of clean energy.

That ability has investors scrambling to bet on the technology. This week, Inertia Enterprises announced a $450 million Series A round that includes Bessemer and GV. In January, Type One Energy told TechCrunch it was in the midst of raising $250 million, while last summer Commonwealth Fusion Systems raised $863 million from investors including Google and Nvidia. Helion itself raised $425 million last year from a group that included Sam Altman, Mithril, Lightspeed, and SoftBank.

While many other fusion startups are targeting the early 2030s to put electricity on the grid, Helion has a contract with Microsoft to sell it electricity starting in 2028, though that power will come from a large commercial reactor called Orion that the company is currently building, not Polaris.

Each fusion reactor has its own events based on the design of its reactor. Commonwealth Fusion Systems, for example, needs to heat its plasma to over 100 million degrees C inside a tokamak, a donut-shaped device that uses powerful magnets to contain the plasma.

The Helion reactor is different, requiring twice as hot plasmas to function as intended.

The company’s reactor design is a so-called field-reversed configuration. The inner chamber looks like an hourglass, and at the wide ends, fuel is injected and converted into plasma. The magnets then accelerate the plasmas towards each other. When they first come together, they are around 10 million to 20 million degrees C. Strong magnets then compress the fused ball, raising the temperature to 150 million degrees C. It all happens in less than a millisecond.

Instead of releasing energy from fusion in the form of heat, Helion uses the magnetic field of the fusion reaction to generate electricity. Each pulse will repulse the reactor’s magnet, drawing an electrical current that can be harvested. By harvesting electricity directly from the fusion reaction, the company hopes to be more efficient than its competitors.

Last year, Kirtley said Helion refined some of the circuits in the reactor to increase how much electricity they get.

While the company uses deuterium-tritium fuel today, down the road it plans to use deuterium-helium-3. Many fusion companies plan to use deuterium-tritium and release the energy as heat. Helion’s fuel of choice, deuterium-helium-3, produces highly charged, magnetically repulsive particles that block the plasma, making it a better fit for Helion’s method of direct electricity generation.

Helion’s main goal is to produce plasmas up to 200 million degrees C, which is much higher than the goals of other companies, a function of its reactor design and fuel selection. “We believe that as you get to 200 million degrees, that’s when you get into that area where you want to use a power plant,” Kirtley said.

When asked if Helion has reached scientific separation — the point at which the fusion reaction produces more energy than is needed to start it — Kirtley demurred. “We focus on the piece of electricity, making electricity, rather than pure science.”

Helium-3 is common on the Moon, but not here on Earth, so Helion must make its own fuel. To start, it will combine deuterium nuclei to produce the first clusters. In normal operation, while the main source of energy will be deuterium-helium-3 fusion, another reaction will still be deuterium-on-deuterium, which will produce helium-3 that the company will purify and reuse.

Work has begun to refine the fuel cycle. “It was a pleasant surprise that a lot of the technology was easier to do than we expected,” said Kirtley. Helion was able to produce helium-3 with “very high efficiency in terms of both yield and purity,” he added.

Although Helion is currently the only fusion startup using helium-3 in its fuel, Kirtley said he thinks other companies will do so in the future, noting that he would be open to selling it to himself. “Some people – as they come and realize that they want to do this direct energy recovery method and see the benefits that come from it – they will want to use helium-3 fuel,” he said.

Alongside its Polaris experiments, Helion is building Orion, the 50-megawatt fusion reactor it needs to fulfill its Microsoft contract. “Our ultimate goal is not to build and deliver Polaris,” Kirtley said. “That’s a step on the way to scaled power plants.”