The quest for commercially viable fusion energy took a significant step forward this week as Helion Energy announced it has achieved a plasma temperature of 150 million degrees Celsius within its Polaris prototype reactor. This milestone, revealed on , represents three-quarters of the temperature Helion believes is necessary for a functioning commercial fusion power plant.
“We’re obviously really excited to be able to get to this place,” said David Kirtley, Helion’s co-founder and CEO, in a statement to TechCrunch. The achievement isn’t just about reaching a high temperature; it’s about the fuel being used to get there. Polaris is the first fusion reactor to operate using deuterium-tritium fuel, a mixture of two hydrogen isotopes. According to Kirtley, the team observed a “dramatic” increase in fusion power output in the form of heat as expected.
The race to commercialize fusion power is attracting substantial investment. Fusion promises a potentially limitless source of clean energy, and several companies are vying to be the first to deliver it. This week alone saw Inertia Enterprises secure $450 million in Series A funding, while Type One Energy is reportedly raising $250 million. Commonwealth Fusion Systems previously raised $863 million, and Helion itself secured $425 million last year.
Helion’s approach differs from many other fusion startups. While most are aiming for grid-connected electricity in the early 2030s, Helion has a contract with Microsoft to begin delivering power in . However, this initial power supply will come from Orion, a larger commercial reactor currently under construction, not the Polaris prototype.
The core of Helion’s technology lies in its unique reactor design, a “field-reversed configuration.” Unlike the more common tokamak design – a doughnut-shaped device utilizing powerful magnets – Helion’s reactor resembles an hourglass. Fuel is injected and converted into plasma at the wide ends, then accelerated towards each other using magnets. The initial merger occurs at temperatures between 10 and 20 million degrees Celsius. Further compression by powerful magnets then elevates the temperature to the recently achieved 150 million degrees Celsius, all within less than a millisecond.
A key distinction for Helion is its method of energy extraction. Instead of relying on heat generated by the fusion reaction, Helion aims to directly convert the fusion reaction’s magnetic field into electricity. The fusion pulse pushes against the reactor’s magnets, inducing an electrical current that can be harvested. This direct energy conversion, the company believes, will lead to greater efficiency.
Over the past year, Helion has focused on refining the reactor’s circuits to maximize electricity recovery. Looking ahead, the company plans to transition from deuterium-tritium fuel to deuterium-helium-3. While most fusion companies are focused on deuterium-tritium and heat extraction, Helion’s fuel choice is designed to complement its direct electricity generation approach. Deuterium-helium-3 fusion produces more charged particles, which interact more strongly with the confining magnetic fields, enhancing the efficiency of the direct energy conversion process.
Helion’s ultimate goal is to reach a plasma temperature of 200 million degrees Celsius, exceeding the targets of many competitors. “We believe that at 200 million degrees, that’s where you get into that optimal sweet spot of where you want to operate a power plant,” Kirtley explained.
When asked about achieving “scientific breakeven” – the point where a fusion reaction generates more energy than it consumes – Kirtley shifted the focus. “We focus on the electricity piece, making electricity, rather than the pure scientific milestones.”
Helium-3 is scarce on Earth but abundant on the Moon. Helion plans to initially produce its own helium-3 by fusing deuterium nuclei. In regular operation, the process will involve deuterium-helium-3 fusion, with some deuterium-on-deuterium reactions generating additional helium-3 for purification and reuse.
The company reports promising progress in refining this fuel cycle, achieving “very high efficiencies” in both throughput and purity. Currently, Helion is the only fusion startup utilizing helium-3, but Kirtley anticipates others will follow suit as they adopt direct electricity recovery methods. He even suggested a willingness to supply helium-3 to competitors in the future, stating, “Other folks…will want to be using helium-3 fuel as well.”
While Polaris serves as an experimental platform, Helion is simultaneously building Orion, a 50-megawatt fusion reactor designed to fulfill its contract with Microsoft. “Our ultimate goal is not to build and deliver Polaris,” Kirtley emphasized. “That’s a step along the way towards scaled power plants.”
