A Washington State company building pulsed field-reversed configuration devices with the aim of generating electricity through direct energy conversion from deuterium-helium-3 fusion. Helion signed a power purchase agreement with Microsoft in 2023.
Helion Energy was founded in 2013 in Redmond, Washington, by David Kirtley, Chris Pihl, George Votroubek, and John Slough. The founders had backgrounds in plasma physics and field-reversed configuration research, with roots in work conducted at the University of Washington and MSNW LLC, a prior research entity.1
The company is now headquartered in Everett, Washington, where it occupies a large facility for the construction and testing of its fusion prototypes.
Helion uses a pulsed field-reversed configuration (FRC) approach combined with magneto-inertial compression. Two FRC plasmoids are formed at opposite ends of a linear device and accelerated toward each other at high velocity. They collide and merge at the center, where a set of external magnets rapidly compresses the merged plasmoid to fusion conditions.2
The pulsed nature of the system means it operates in rapid cycles, with each compression event lasting microseconds. The company aims for a repetition rate of approximately one pulse per second in a power-producing reactor.
Helion has built a series of increasingly capable prototypes, each designated by generation number. The sixth-generation machine, Trenta, operated from 2020 and the company reported achieving plasma temperatures over 100 million degrees Celsius — a claim the company published but which has not been independently verified through peer-reviewed publication as of mid-2025.3
Helion's profile rose dramatically in 2023 with two announcements. First, it closed a $500 million Series E funding round led by Sam Altman, CEO of OpenAI, who also personally invested and joined the board. Total funding exceeds $570 million. Second, Helion signed a power purchase agreement (PPA) with Microsoft, committing to deliver fusion-generated electricity by 2028 — the first such commercial agreement in the fusion industry.4
Helion is currently building its seventh-generation machine, Polaris, designed to demonstrate net electricity generation from fusion for the first time. The company has stated that Polaris will be the machine that fulfills the Microsoft PPA obligation.5
Several significant technical challenges remain. Sourcing helium-3 fuel at scale is a known difficulty, though Helion has stated it plans to breed helium-3 from deuterium-deuterium reactions within the device itself. The feasibility of achieving the required plasma conditions, demonstrating net energy gain, and operating at the pulse rates needed for continuous power production are all undemonstrated at the required scale.
Helion represents one of the most aggressive timelines and unconventional architectures in private fusion. Its combination of pulsed FRC, D-3He fuel, and direct energy conversion is unique in the industry. The Microsoft PPA has placed the company under significant public scrutiny regarding its ability to deliver on its stated timeline.