I can give this a shot. There is a sort of simpler explanation of what happens in a stellarator, or at least, why the shape is so weird:<p>When a plasma is confined in a torus, it is spinning (naturally). However, this creates an effective centrifuge, which means that the hottest atoms -- which are also the &quot;lightest&quot; -- will move towards the outside of the ring, and ultimately will escape confinement. This cools the plasma.<p>The stellarator solution is basically to turn the torus into a Möbius strip, so that ions which have drifted outside are naturally shuttled to the inside (for the same reason that the &quot;inside&quot; and &quot;outside&quot; of a Möbius strip are the same). However, in order to retain rotational symmetry, the strip has five twists, rather than just one (the topology remains the same).<p>Unfortunately, calculating the dynamics of a plasma shaped like this is hard -- really hard. It requires good computers, so for many years stellarators were mostly an object of theoretical interest. Additionally in order to deal with other instabilities the Wendelstein has an even more refined shape than the five-twisted strip.<p>ITER was conceived in 1987, and at the time it was necessary to go with a technology that was well-tested and understood, and which people felt confident would perform as expected. At that time, using a stellarator made as much sense as writing Firefox OS in Rust or something.