Commonwealth Fusion Systems, the Massachusetts-based spin-out from MIT, secured $863 million in a Series B2 round backed by Nvidia’s NVentures, Google, Breakthrough Energy Ventures, Khosla Ventures and funds tied to Bill Gates. The financing also drew in a consortium of 12 Japanese companies led by trading houses Mitsui & Co. and Mitsubishi Corp., as well as institutional investors such as Brevan Howard and Morgan Stanley’s Counterpoint Global. The new capital lifts CFS’s total funding to roughly $3 billion, the largest war chest in the burgeoning fusion sector. Chief Executive Officer Bob Mumgaard said the money will help complete SPARC, a superconducting-magnet demonstration reactor under construction in Devens, Massachusetts, and keep development on track for ARC, the company’s first commercial plant. CFS aims to switch on SPARC next year and reach scientific breakeven—producing more energy than it consumes—by 2027. Subject to those milestones, the company plans to begin building ARC in Virginia as early as 2027–28 and deliver electricity to the grid in the early 2030s. Google has already agreed to purchase 200 megawatts of output from the first plant, while the Japanese investors are expected to collaborate on supply-chain and manufacturing partnerships.