An international team of scientists is running tests on the largest and most sophisticated stellarator, the Wendelstein 7-X fusion experiment. This complex machine is housed at the Max-Planck-Institute of Plasma Physics in Greifswald, Germany. Besides preparing for new experiments, researchers are analyzing data from the first experiment campaign that took place in 2016, hoping to understand the science of fusion reactors. In a new report in Physics of Plasmas, from AIP Publishing, Shaocheng Liu and his collaborators recount the first detailed characterization of plasma turbulence at the outer edge of the stellarator.
In Wendelstein 7-X, helium is ionized and heated to 50 million degrees Celsius where it is confined by strong superconducting magnets, which are cooled to minus 270 degrees Celsius. The superconducting magnets create helical magnetic field lines that have been carefully optimized so that fast-moving charged particles remain trapped on a toroidal surface. Like other magnetic confinement devices, turbulence appears in the heated plasma that causes heat and particles to wander across these surfaces and ultimately come into contact with the first wall surrounding the plasma. The characteristics of this turbulence are critical to understanding how to build energy-producing reactors in the future.
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