Last month, a fusion reactor in China successfully contained steady-state plasma for more than 17 minutes, pushing humanity one step closer to achieving a limitless source of energy, according to a press release from the Chinese Academy of Sciences. The Experimental Advanced Superconducting Tokamak in Hefei is one of 40 fusion reactors being developed across the world. All of them are trying to recreate the power of the sun, here on Earth. A fusion reactor could generate nearly four million times more energy than burning oil or coal, according to the International Atomic Energy Agency (IAEA), a United Nations organization that promotes the peaceful use of nuclear technology.
Plasma, a gaseous collection of positive ions and roving electrons, is the fourth state of matter and powers the fusion of stars. But in a fusion reactor, the plasma needs to get to 180 million degrees Fahrenheit, about 10 times hotter than the sun. The gases are so hot that electrons break free of their attachment to the atomic nuclei, the dense area containing protons and neutrons at the center of atoms. Then two nuclei collide with each other and fuse into a single, heavier nucleus. Each time this merging happens, it releases a colossal amount of energy. Just a few grams of deuterium and tritium—hydrogen atoms that contain extra neutrons and that would power tokamaks—would produce a terajoule of energy, according to the IAEA. That’s roughly what one person in a developed country needs over sixty years.
But fusion reactions aren’t sustainable unless scientists figure out how to keep the plasma stable.
Plasma’s inherent electrical charge–made up of the positively charged ions and negatively charged electrons–means that if the plasma touches anything, it cools and falls apart, like water from a popped balloon. To enable controlled fusion reactions, hollow doughnut-shaped reactors called tokamaks contain powerful magnets that confine and compress the plasma’s path, before swirling it around the tokamak to start a fusion reaction. If scientists achieve that plasma stability for long enough, each fusion reaction could provide enough heat to power up the next one, creating a perpetual cycle of energy creation—the ultimate aim of a carbon-zero fusion engine.
So far, we don’t have magnetic fields that are both powerful and small enough to sustain a reaction for longer than a few billionths of a second.
Recently, researchers at Tokamak Energy in the U.K. tested a novel superconductor technology that could be groundbreaking for tokamaks struggling to contain plasma. A superconductor is a material that can conduct electricity with zero energy loss when it’s cooled to a certain temperature. Since it has virtually no electrical resistance, a superconductor can provide the magnetic magic that holds the plasma in place. The U.K. researchers bonded a thin layer of supercooled rare-earth barium copper oxide, known as REBCO, to copper metal tape that they wound hundreds of times around. Then they ran 1,000 amps of electrical current through the windings, creating a model of a superconducting toroidal field coil. This powerful, compact field coil is used to generate an extremely powerful magnetic field in a fusion reactor. Tokamak Energy hopes to bid on the UK’s Spherical Tokamak for Electricity Production, which aims to become a practical demonstration of a fusion reactor.
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