HSX (or the Helically Symmetric Experiment) is an entirely new type of stellarator fusion experiment that combines the best attributes of two existing technologies.

The shape of HSX is its signature and the key to its unique properties. The vacuum chamber looks like a warped donut, with a series of helical twists and turns girdled by thick coils of copper magnets. The device will confine plasmas in a magnetic field, while generating temperatures of up 10 million degrees.

Although it may be decades from application, fusion holds tremendous promise as an alternative energy source. The same way the sun creates energy, fusion is achieved by melding atomic nuclei of two elements under extremely high temperatures, which releases energy, without any polluting byproducts.

Fusion fuel is essentially sea water, and one gallon burned in a fusion reactor would produce the equivalent energy of burning 300 gallons of gasoline. HSX combines elements of two existing styles of plasma containment experiments known as tokamaks and stellarators. Tokamaks have achieved the best results to date, but they also require a strong current in the plasma itself. Stellarators don’t need that current, making them potentially more attractive as power reactors.

But they don’t produce the high-quality magnetic field that confines plasmas to reach higher temperatures. HSX solves that problem by achieving symmetry in the magnetic field through its oddly shaped and complex magnet coils. The plasma-confining energy is located in coils outside of the plasma itself, making it a more stable and attractive as a reactor.

HSX is still in its infancy. “The first plasma really marks the line between the construction and the research phase,” says associate scientist Joseph Talmadge

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