It's already being built. https://www.technologyreview.com/2022/02/23/1045122/fusion-power-mit-startup-commonwealth/

By some point in 2025, the scientists at Commonwealth Fusion Systems expect, their machine will blow past that threshold, generating 10 times more energy than it consumes. That demonstration, they say, will enable the startup to develop full-size facilities capable of delivering as much electricity as a small coal plant by the early 2030s.

A new type of magnetic containment technology developed a decade ago is responsible for making this a [soon to be] reality.