Helically Symmetric Experiment
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| Major radius | 1.2 m |
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| Minor Radius | 15 cm |
| Heating | 100 kW (ECH) |
The Helically Symmetric Experiment (HSX), stylized as Helically Symmetric eXperiment, is an experimental plasma confinement device at the University of Wisconsin-Madison, with design principles that are hoped to be incorporated into a fusion reactor. The HSX is a modular coil stellarator which is a toroid-shaped pressure vessel with external electromagnets which generate a magnetic field for the purpose of containing a plasma.
A stellarator is a magnetic confinement fusion device which generates all required magnetic fields to confine high temperature plasma by external magnetic coils. Unlike in tokamaks and reversed field pinches, no toroidal plasma current is required in stellarators to confine the plasma. Lack of this large externally driven plasma currents makes stellarators suitable for steady-state fusion power plant. However, due to non-axisymmetric nature, conventional stellarators have a combination of toroidal and helical modulation of the magnetic field on a magnetic field line that leads to high transport of plasma out of the confinement volume at fusion relevant conditions. This large transport in conventional stellarators can limit their performance as a fusion reactor.
This problem can be largely reduced by tailoring the magnetic field geometry. The dramatic improvements in computer modeling capability in the last two decades has helped to "optimize" the magnetic geometry to reduce this transport, resulting in a new class of stellarators called "quasi-symmetric stellarators". Computer-modeled odd-looking electromagnets will directly produce the needed magnetic field configuration. These devices combine the good confinement properties of tokamaks and the steady-state nature of conventional stellarators. The Helically Symmetric Experiment (HSX) at the University of Wisconsin-Madison is such a quasi-helically symmetric stellarator (helical axis of symmetry).
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