Operational
Polaris
7th-generation fusion prototype designed to demonstrate electricity production from fusion using Helion's pulsed magneto-inertial architecture and direct electricity recapture.
Helion EnergyTiny Merge
Under Construction
Smaller, agile FRC fusion testbed roughly one-eighth the size of Polaris (~8 feet long) used to iterate on plasma formation and ring-merging experiments far faster than the larger machines. Helion sees Tiny Merge as a key learning loop to de-risk Orion ahead of the 2028 Microsoft delivery deadline.
Latest update Sep 16, 2026
01
Current status
Helion completed the first vacuum pump-down on Tiny Merge at its Everett campus on August 28, 2026, reaching 1x10-6 torr in under an hour. CEO David Kirtley's June 2026 subscale-systems blog, still the latest company description as of September 16, 2026, says the team has begun integrating Tiny Merge to run in parallel with Polaris. Remaining hardware is still being installed. The end-of-summer 2026 online target was not met; the testbed is now expected online later in 2026 so its faster experimental loop can still feed Orion design choices.
02
Specifications3
03
Upcoming milestones1
Announced next steps from Helion Energy that mention Tiny Merge.
Late 2026
Bring Tiny Merge online and use it to inform Orion
Stand up the Tiny Merge agile testbed and use its faster experimental loop to lock in final FRC formation and ring-merging choices that flow into the Orion power plant design. On August 28, 2026 Helion completed the first vacuum pump-down, reaching 1x10-6 torr in under an hour. CEO David Kirtley's subscale-systems blog still describes Tiny Merge as being integrated in parallel with Polaris. Remaining hardware is still being installed at the Everett campus. The end-of-summer 2026 online target was not met; as of September 16, 2026 Helion has not announced first plasma or a fully online experimental campaign.
04
In the news2
Helion completes first Tiny Merge vacuum pump-down
Helion said on August 28, 2026 that it completed the first vacuum pump-down on Tiny Merge, its subscale field-reversed-configuration fusion testbed at the Everett, Washington campus, reaching a target base pressure of 1x10-6 torr in under an hour. The company said the result confirms the machine can hold high vacuum before remaining hardware is installed. Tiny Merge is roughly one-eighth the size of the Polaris prototype and is meant to iterate on plasma formation and merging faster ahead of Helion's 2028 Microsoft power-delivery deadline for the Orion plant.
Helion raises $465M Series G at $15.5B fusion valuation
Helion Energy on June 4 closed a $465 million Series G led by Thrive Capital at a $15.5 billion post-money valuation, lifting total funding to roughly $1.5 billion as the Everett, Washington startup races to deliver fusion electricity to Microsoft from its Orion plant in Malaga by 2028. New investors include Lux Capital, Peak XV Partners, Alta Park Capital, Anti Fund, BoxGroup and Ford Motor Executive Chairman Bill Ford, joining existing backers SoftBank Vision Fund 2, Lightspeed, Mithril, Capricorn and Good Ventures; the cash will scale manufacturing and feed the Polaris prototype and forthcoming Tiny Merge testbed campaigns.
05
More from Helion Energy2
06
More in Nuclear Fusion
Under ConstructionSPARC
Commonwealth Fusion Systems
Compact, high-field tokamak designed to demonstrate net energy from fusion. It uses high-temperature superconducting magnets to achieve reactor-class magnetic fields in a much smaller machine, with peer-reviewed projections of roughly Q ~11 and ~140 MW of fusion power.
In DevelopmentARC (Fall Line Fusion Power Station)
Commonwealth Fusion Systems
CFS' first planned grid-scale commercial fusion power plant, designed to deliver about 400 MW of clean electricity using the HTS magnet and tokamak stack proven through SPARC. The project is officially named the Fall Line Fusion Power Station and is planned for a 100-acre site at the James River Industrial Center in Chesterfield County, Virginia.
OperationalNorm
TAE Technologies
TAE's streamlined fusion research machine that forms field-reversed-configuration plasmas using only neutral beam injection, reducing reactor size, complexity, and cost versus Norman while preserving the path to commercial hydrogen-boron fusion.
In DevelopmentDa Vinci
TAE Technologies
TAE's first prototype commercial fusion power plant, designed to deliver net electrons to the grid from the company's hydrogen-boron fusion pathway and serve as the bridge to later utility-scale plants.