Thea Energy, a fusion startup spun out of Princeton's Plasma Physics Laboratory, has raised an oversubscribed $100 million Series B led by U.S. Innovative Technology Fund, the company told TechCrunch. The fresh cash catapults Thea into the upper echelons of fusion startup funding, giving it a fighting chance at building a commercial reactor before humanity runs out of patience.

The new funding will help Thea expand manufacturing for its uniquely designed smaller magnets and begin construction of Eos, its “power plant relevant” demonstration device, starting next year. Thea previously closed a $20 million Series A in early 2024, bringing total private investment to $130 million - enough to make any physicist consider switching careers.

Magnets are at the core of many fusion power plant designs - they keep the superheated plasma compressed and burning hot enough to fuse atoms, releasing heat and energy. But Thea’s magnets are different: each rectangular magnet can be tuned to create the reactor’s overall magnetic field shape. Thea likens these to pixels in a computer monitor, which collectively follow software instructions to create text and images. Because nothing says “controlled nuclear fusion” like a metaphor about your screen's resolution.

For Thea, flexibility is key. Its reactor design is a stellarator, capable of keeping plasma in very stable configurations but requiring twisty, bendy shapes to accommodate the plasma. This contrasts with tokamaks, which use brute force to keep plasma confined - like a bouncer at a nightclub. The irregular shape of a stellarator drives up complexity and cost for magnet manufacturing. Thea is betting that by shrouding its reactor core in dozens of regular magnets, it can use software to create a stellarator-shaped magnetic field inside a much simpler physical structure. The software should also help with assembly: Thea has purposefully installed test magnets out of alignment, and the software compensated. So far, the magnets haven't developed an attitude.

Thea hopes to complete its Eos demonstration reactor in 2030, with a commercial version called Helios coming online in 2034. That timeline puts it neck-and-neck with competitors like Commonwealth Fusion Systems, which aims to bring its Arc reactor online in Virginia in the early 2030s. Fusion race, anyone?

If Thea’s pixel-inspired magnets work, the company could enjoy a manufacturing advantage. The startup has built dozens of iterations of its full-scale magnets in its lab in Jersey City, while other fusion startups have had to build massive assembly halls to make reactor-scale magnets. Yet there are already signs that the planar coil design has reached its limits. Thea originally called for only planar coils when it spun out of Princeton, but added 12 large magnets of four different shapes outside the planar coils to handle most of the plasma confinement. The 300-plus smaller magnets now serve to fine-tune the plasma. Being reliant on larger magnets erodes the company’s manufacturing advantage to some extent - like winning a marathon but needing a wheelchair for the last mile.

Still, any simplification of a fusion reactor - already among the most complex devices ever made by humans - will help pave the road to fusion power. An extra $100 million doesn’t hurt, either. Other investors in the round include General Innovation Capital Partners, Linse Capital, Calm Ventures, Climate Capital, Divergent Capital, Emerald Technology Ventures, Gaingels, Idemitsu Kosan, Overlay Capital, Timescale Ventures, and Whatif Ventures.