Researchers have made important progress in nuclear fusion. A new type of superconducting magnet that can be used in fusion reactors has been successfully tested.
An artificial sun on Earth – this dream of a virtually inexhaustible source of energy through nuclear fusion has been driving researchers for decades. The fusion of atomic nuclei of hydrogen and its isotopes deuterium and tritium to form helium nuclei releases enormous amounts of energy in stars like the Sun. The long-held goal of building a fusion power plant that produces more energy than it consumes could solve many of our energy problems in one fell swoop. The big advantage of this type of energy production: The fuel for fusion could be obtained from seawater and is available in virtually unlimited quantities. In addition, electricity could be produced without emitting greenhouse gases and producing radioactive waste.
In order for nuclear fusion to begin, the fuel in the fusion reactors must be brought to high temperatures and pressures. The hot plasma is kept in a suspended state using strong magnets, as no material would be able to withstand contact with the fuel, which is millions of degrees hot. The powerful electromagnets used for this consist of superconducting coils. To date, the best superconducting magnets have been powerful enough to bring the plasma to fusion energy and safely confine it – but only at sizes and costs of construction that were not within the practical or economically efficient range.
Newly researched technology
In September 2021, scientists at the Massachusetts Institute of Technology (MIT) achieved a major success in fusion research. They developed a new type of magnet that would be suitable for future fusion power plants. “You’re essentially reducing the cost per watt of a fusion reactor by a factor of almost 40 in a day. Now fusion has a chance,” explains MIT’s Dennis Whyte. Superconducting magnets rely on a temperature close to absolute zero (-273.15 degrees Celsius). While previous fusion magnets required cooling to around 4 Kelvin, the newly researched magnetic material called REBCO (rare-earth barium copper oxide) becomes conductive without resistance at just 20 Kelvin. This may sound like a small difference at first, but it brings significant advantages in terms of material properties and practical technology, as the scientists explain. Furthermore, the REBCO magnets are easier to install. They do not require an additional insulator, which allows space for additional components to be installed for cooling or to increase strength.
Successful testing procedure
In initial tests of their new REBCO magnets, the research team intentionally created unstable conditions, for example by turning off power to the cooling device. This is often considered a bad scenario for the fusion magnets as they can be destroyed due to overheating. The picture shows the experimental setup including the new superconducting magnets at MIT.
To the delight of the scientists, positive results emerged. “Essentially, we intentionally did the worst possible thing to a coil after testing every other aspect of coil performance. And we found that most of the coil survived without damage,” explains Whyte. The successful testing of the newly discovered magnet was “the most important thing in fusion research in the last 30 years,” he summarizes.