A third dimension helps Tokamak fusion reactor avoid wall-destroying instability
Enlarge / Currents and fields in the KSTAR Tokamak. (credit: Jong-Kyu Park)
The success of Tokamaks for fusion is a story unto itself, with the toroidal magnetic containers setting records for keeping high-energy plasmas under control, a necessary step for sustaining fusion. The overriding narrative, at least on the scientific side, is that when you have an unstable plasma, it is really hard to build a control system that keeps the plasma hot and confined, even in a Tokamak.
Now, researchers have used the Korean KSTAR Tokamak to show that they can gain control of a particularly nasty plasma instability called an edge localized mode. The instability essentially exhausts the plasma onto the wall, ablating it away. If a plasma reactor the size of ITER were to have an edge localized mode instability, it would likely destroy the inner lining of the vacuum vessel.
Symmetries giveth, symmetries takethI don't pretend to understand plasma instabilities in a Tokamak very well. But I do know that some of the problems are the result of the shape of the magnetic field. The shape of the Tokamak is a boon: it's symmetric, which makes the device simple, it makes calculations possible, and it offers high confinement.
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