Commonwealth Fusion Systems develops high-temperature superconducting magnets using REBCO tape to enable compact tokamak fusion reactors capable of 20-tesla magnetic fields. The company manufactures these magnets at its Devens, Massachusetts facility and is building SPARC, a tokamak demonstration machine fueled by deuterium-tritium plasma to achieve net energy gain with Q>1, with operations targeted for 2026. It plans to construct ARC, a grid-scale fusion power plant producing 400 MWe set to come online in Virginia in the early 2030s. Google has committed to purchasing 200 MW of electricity from ARC, and the company maintains a strategic partnership with Dominion Energy. CFS raised $863 million in its Series B2 funding round in August 2025, following a $1.8 billion Series B in 2021 from Temasek Holdings, Google, Breakthrough Energy Ventures, and Eni, for a total close to $3 billion. Bob Mumgaard serves as CEO and co-founder with a PhD in plasma physics from MIT, while Brandon Sorbom is Chief Science Officer and co-founder with a PhD in plasma physics from MIT.