Tokamak experiments come clean about impurity transport

A fusion reactor operates best when the hot plasma inside it consists only of fusion fuel (hydrogen’s heavy isotopes, deuterium and tritium), much as a car runs best with a clean engine. But fusion fuel reactions at the heart of magnetic fusion reactors also create leftovers—helium “ash.” The buildup of this helium ash and other impurities can cool the hot plasma and reduce fusion power

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Tokamak experiments come clean about impurity transport