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A plasma glows inside MAST, a spherical tokamak.

A plasma glows inside MAST, a spherical tokamak.


Feature: The new shape of fusion

The quest for fusion energy is more than 60 years old and the current great hope, the $18 billion ITER reactor, won't hit its stride until 2027 at the earliest. Surely there is a quicker and cheaper route. Behold the spherical tokamak, a plumped-up version of the mainstream tokamak reactor shaped more like a cored apple than the traditional doughnut. That simple shape change could open the way to a fusion power plant that would match ITER's promise, without the massive scale. The world's two front-rank machines—in the United States and the United Kingdom—are both being upgraded with stronger magnets and more powerful heating systems. Soon they will switch on and heat hydrogen fuel to temperatures much closer to those needed for generating fusion energy. If they perform well, spherical tokamaks could change the shape of fusion's future.

To read the full story, see the 22 May issue of Science.