Fusion Startup Sustains Net-Gain Reaction for Six Minutes

A private fusion company announced Wednesday that its compact tokamak sustained a net-energy-gain plasma for six minutes and twelve seconds, shattering the previous sustained-burn record and shifting the field’s central question from whether fusion works to whether it can run like a power plant.

The result, submitted to a peer-reviewed journal and observed by two national-laboratory teams, produced 1.9 times the energy injected into the plasma. More significant than the gain factor, physicists say, was stability: the reaction rode through multiple disruption precursors that would have ended earlier runs, managed by a machine-learning control system trained on thousands of prior shots.

Six minutes matters because it crosses the threshold where plasma physics stops being the binding constraint. The limiting factors in Wednesday’s run were engineering — heat load on divertor plates and tritium fuel cycling — which are hard problems, but the kind humans have solved before in other industries.

The commercial race is thickening. At least eight companies now operate net-gain-adjacent programs, and utilities have begun signing conditional power-purchase agreements for the late 2030s. Skeptics note, fairly, that fusion history is a graveyard of extrapolated timelines, and that no device has yet produced net electricity — a stricter test than plasma gain.

Still, the mood among plasma physicists is unfamiliar. "For fifty years the joke was that fusion is thirty years away and always will be," one laboratory director said. "Nobody is telling that joke this week."