US nuclear fusion firm begins installing final 48-ton vacuum vessel half for net energy

Commonwealth Fusion Systems has begun final assembly of SPARC after receiving the second half of its 48-ton vacuum vessel.

The reactor is now about 75% complete, with magnets, sensors, cabling, and heat-resistant interior parts being installed.

CFS is targeting operations in 2027, with a key goal of demonstrating net energy gain, or Q>1.

A successful result would be a major milestone for commercially viable fusion and would validate the high-field magnet approach for future reactors like ARC.