Helion is betting big on the ‘Tiny Merge’ fusion testbed to meet Microsoft’s ambitious timeline

EVERETT, Wash.— With just three years to go before a tough deadline to prove its fusion method works, Helion Energy is grappling with important questions — and it’s building a new, smaller machine to help find answers faster.

Since its launch more than a decade ago, Helion has built a growing number of prototype devices to test and refine its fusion technology as it races to deliver an unlimited clean energy source. But by 2028, Helion is contractually obligated to have a commercial facility producing energy from fusion reactions, essentially replicating the physics that powers the sun.

So now it’s slow.

The company is building a scaled-down test machine called “Tiny Merge,” a machine less than one-eighth the size of Polaris, its seventh generation and final prototype. The decision reflects the fact that important issues remain that Helion’s larger, more expensive prototypes have not been fully resolved. These concerns must be addressed before final power plant designs are finalized.

“With this ultra-fast testbed, we’ll be able to test new ideas with much less power and fewer resource requirements, meaning we can iterate faster than we can on full-scale missions like Polaris,” said Michael Hua, Helion’s senior director of radiation safety and nuclear science.

GeekWire caught up with Tiny Merge during a recent visit to the company’s distribution R&D facility north of Seattle. Behind large curtains in an enclosed part of the building sits a shiny device, consisting of tubes about 8 feet long.

Running parallel to the machine are two rows of tall shelves — heavy-duty versions of what you’d find at a home improvement store — that will eventually hold hundreds of small refrigerator-sized capacitors to store power in and out of the device. Helion plans to have Tiny Merge up and running again by the end of the summer, leaving about two years to integrate what it learns into final designs.

The stakes couldn’t be higher. Over in Eastern Washington, Helion broke ground on Orion, a facility it hopes will be the first to produce fusion power on a commercial scale. It’s a feat that no one has yet accomplished, although more than 45 companies are trying.

Helion has made a tighter timeline commitment with an agreement with Microsoft to supply electricity from Orion for data center upgrades starting in 2028. Miss that deadline, and Helion faces financial penalties from Microsoft and its partner Constellation.

The company is counting on Tiny Merge to help make that big bet pay off.

Fusion works by heating matter and compressing it into a plasma, a superheated state where atoms are stripped of their electrons. In those extreme cases, atomic nuclei collide, fuse and release energy. This process holds great promise for more clean energy, but achieving it on a large scale is still a major scientific challenge.

The team’s first experiments with Tiny Merge will focus on the formation and fusion of plasma rings, said Manav Singh, Helion’s director of electrical engineering. The company has researched this with previous prototypes, Singh said, but the new results have raised more questions. “There are a few more in-depth investigations that we want to do,” he added.

Helion and the wider fusion industry have made measurable progress in recent years, with devices hitting new records in temperature and pressure. Companies have poured significant funding into this endeavor, with Helion alone raising more than $1 billion from investors including OpenAI CEO Sam Altman.

But plenty of critics remain, arguing that the potential for grid-scale integration is years away — if it ever arrives.

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