Various types of rare earth magnets play one of the most key roles in the field of modern physics. The magnetic fields they create keep the plasma in the chambers of experimental thermonuclear reactors, with their help, particle flows are accelerated and directed in the tunnels of accelerators, etc. But not all existing electro rare earth magnets have the same characteristics, and recently researchers and engineers at Fermi National Laboratory have developed a new superconducting electromagnet, superior in characteristics to anything that has been previously created in this direction.
In installations such as the Large Hadron Collider, which is the most powerful particle accelerator to date, rare earth magnets must produce a field of at least 8 Tesla. At the same time, the output of the magnet to the operating mode is carried out smoothly at a speed of 0.006 Tesla per second and takes about 20 minutes. In particle accelerators that use copper-wound rare earth magnets , the magnetic field builds up at a much faster rate. For example, the rare earth magnets of the Japanese accelerator J-PARC, which generates the most powerful neutron flux, are capable of increasing field strength at a speed of 70 Tesla per second, and the rare earth magnets of the Fermi laboratory accelerator – at a speed of 30 Tesla per second.
One of the problems that makes it difficult to raise the field of superconducting rare earth magnets at high speed, is the appearance of “hot spots” in the windings, the size of which increases with increasing current and generated magnetic field. With a rapid increase in current, the temperature in these spots increases so much that the material switches from a superconducting state to an ordinary state with electrical resistance, and the magnet loses its effectiveness or stops working altogether.
Scientists from the Fermi laboratory have found a solution in the form of the material YBCO, a complex compound of yttrium, barium, copper and oxygen, a famous high-temperature superconductor. From this material, magnet windings were created, capable of operating at temperatures from 6 to 20 Kelvin and capable of withstanding currents up to 1000 amperes.
In tests, the first prototype of a high-temperature electromagnet showed that it could provide a speed of 290 Tesla per second at a peak magnetic field of 0.5 Tesla. Of course, such a magnetic field strength is far from the 8 Tesla required for particle accelerators, but scientists are confident that they still have the ability to further increase the current through the strong magnets and, accordingly, increase the strength of the generated magnetic field.
Currently, scientists at the Fermi laboratory continue to experiment with their new magnet, testing various modes of its operation and upgrading the used power source. And perhaps in the future, similar rare earth magnets will be installed in new experimental facilities, including neutrino detectors and the next generation collider with a 100-kilometer ring of the Future Circular Collider.