Fusion Experiment Demonstrates Cheaper Stellerator Using Creative Magnet Workaround

Popular Science reports that early last week, researchers at the U.S. Energy Department's Princeton Plasma Physics Laboratory revealed their new "MUSE" stellarator - "a unique fusion reactor that uses off-the-shelf and 3D-printed materials to contain its superheated plasma." The researchers' announcement says the technique suggests "a simple way to build future devices for less cost and allow researchers to test new concepts for future fusion power plants."Stellarators typically rely on complicated electromagnets that have complex shapes and create their magnetic fields through the flow of electricity. Those electromagnets must be built precisely with very little room for error, increasing their cost. However, permanent magnets, like the magnets that hold art to refrigerator doors, do not need electric currents to create their fields. They can also be ordered off the shelf from industrial suppliers and then embedded in a 3D-printed shell around the device's vacuum vessel, which holds the plasma. "MUSE is largely constructed with commercially available parts," said Michael Zarnstorff, a senior research physicist at PPPL. "By working with 3D-printing companies and magnet suppliers, we can shop around and buy the precision we need instead of making it ourselves." The original insight that permanent magnets could be the foundation for a new, more affordable stellarator variety came to Zarnstorff in 2014. "I realized that even if they were situated alongside other magnets, rare-earth permanent magnets could generate and maintain the magnetic fields necessary to confine the plasma so fusion reactions can occur," Zarnstorff said, "and that's the property that makes this technique work." [...] In addition to being an engineering breakthrough, MUSE also exhibits a theoretical property known as quasisymmetry to a higher degree than any other stellarator has before. It is also the first device completed anywhere in the world that was designed specifically to have a type of quasisymmetry known as quasiaxisymmetry. Conceived by physicist Allen Boozer at PPPL in the early 1980s, quasisymmetry means that although the shape of the magnetic field inside the stellarator may not be the same around the physical shape of the stellarator, the magnetic field's strength is uniform around the device, leading to good plasma confinement and higher likelihood that fusion reactions will occur. "In fact, MUSE's quasisymmetry optimization is at least 100 times better than any existing stellarator," Zarnstorff said. "The fact that we were able to design and build this stellarator is a real achievement," said Tony Qian, a graduate student in the Princeton Program in Plasma Physics, which is based at PPPL. Also covered by Gizmodo.Thanks to Slashdot reader christoban for sharing the news.

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