Contact: David Larbalestier
TALLAHASSEE, Fla. — The MagLab has done it again.
The U.S. National Science Foundation facility, officially known as the National High Magnetic Field Laboratory and headquartered at Florida State University, has pushed the upper limits of direct current magnetic fields, setting a new world record.
This latest record was achieved with a miniature electromagnet with the moniker "Little Big Coil." About the size of a salt shaker, this experimental magnet generated 17.6 tesla inside the lab’s existing 31 tesla resistive magnet to generate a total field of 48.7 tesla, topping the previous record of 45.5 tesla. Tesla is the unit for measuring magnetic field strength. The new record is almost 50 times stronger than a junkyard magnet capable of lifting a car.
Wound with a superconductor known as REBCO (REBa2Cu3O7-δ) able to carry electricity without resistance, this prototype magnet could lead to smaller, more powerful electromagnets for technology like aircraft motors, fusion reactors, and medical imaging machines.
The white section at the bottom is the 720-feet of superconducting wire coiled tightly to carry electricity in the "Little Big Coil" magnet.
Although this is a test coil, it is a proof of principle that superconducting magnets can top the field of the MagLab's flagship, the behemoth 45 tesla hybrid, which held a Guinness record for highest continuous magnetic field in the world for more than 20 years.
"This is what we do," said MagLab Director Kathleen Amm in celebrating the new achievement. "We push the boundaries to build the strongest magnets in the world for research, and to advance technology that transforms our world. I’m so proud of our team."
Scientists at the MagLab's Applied Superconductivity Center reached the milestone in a collaborative project supported by the Department of Energy Office of Fusion Energy Sciences.
"When the NSF and DOE join forces at NSF MagLab, we don’t just chase records—we break them," said NSF Materials Research Division Director Germano Iannachione. "This high-field DC magnet pushes the boundaries of superconducting science and pulls new possibilities into reach for national security, energy, and beyond."
The small electromagnet is able to carry much higher current and reach such high magnetic fields because it has no insulation and therefore can carry more electrical current, a technology invented by Professor Seungyong Hahn. At the FAMU-FSU College of Engineering, Hahn and Professor David Larbalestier began collaborating to utilize no-insulation windings to try for new world record fields even with tiny magnets. The no-insulation method has been widely embraced by many groups winding REBCO magnets, including two of the leading tokamak fusion power plant manufacturers.
"Obviously, this is another important milestone in the history of high field REBCO magnet technology, an outcome after close collaboration among international teams over a decade," said Hahn, now at Seoul National University, "We have newly identified so many unknowns and together overcome the consequent challenges to come this far."
"This was not just a little world record, to beat the previous mark of 45.5 T by more than three tesla, it’s amazing," said Larbalestier, who is also MagLab Chief Materials Scientist, "This coil is little in size, but it's big in field and big in stress."
With a diameter of about an inch and a half and standing two inches tall, the Little Big Coil is tiny enough to hold in your hand. But packed into that small package is more than 720 feet of a superconducting wire precision-manufactured by the Japanese company Faraday Factory.
"This is an outstanding accomplishment," said Sergey Lee, CEO of Faraday Factory Japan, "We are proud to have contributed our superconductor material and expertise for it."
A previous version of the test coil reached a record 45.5 tesla in 2017. The coils face challenges with mechanical and thermal stresses that all electromagnets must overcome – as they ramp up, the stress on a magnet grows quadratically and the coil can overheat and tear itself apart. The new coil benefitted from tooling and mechanical design done in collaboration with the Magnet Science and Technology Division of the MagLab for the earlier 45.5 T coil.
"MS&T is proud to have collaborated on establishing the Little Big Coil test platform from which we expect many more successes going forward," said Tom Painter, director of the MS&T team.
To help protect this newest coil, ASC research faculty scientist Jeseok Bang wound the superconductor in tight loops more than 2,700 times and focused on smoothing the copper joints that connect one strand to the next. Bang’s meticulous magnet making took more than two months, but his work helped lower resistive heating at the not-superconducting joints — the dissipation of energy through heat limits performance and damages the magnet.
"That is the key difference between the previous one and this new coil. I was able to reduce the resistance by a factor of five" Bang explained.
Applied Superconductivity Center researcher Jeseok Bang with the prototype “Little Big Coil” magnet that reached a record 48.7 tesla.
It was the culmination of years of design, computer modeling, testing, and innovation in construction to improve performance.
"It’s all these little things that you have to do and he has really, really been persistent," added Larbalestier. "What's remarkable is that this is a testbed which is quite inexpensive, by which we can really take the best conductors anybody in the world can make, and then we really test them to their limits."
The new record is just the latest in a steady stream of advances for superconducting materials, which have potential applications in many areas. The Applied Superconductivity Center is helping to build new and improved electromagnets for the Large Hadron Collider particle accelerator. Its engineers are also collaborating with fusion companies building powerful superconducting magnets for experimental reactors.
"This is a technology that people want to use for fusion. They want to use it for electric motors for aircraft," explained Larbalestier. "They want to use it for all sorts of things. So, a demonstration that you really can do something unique and world-record breaking successfully, though not easy, has great potential to galvanize attention for many applications."
The challenge is manufacturing high-quality, high-performance superconducting wire free of defects that can withstand the extreme forces of high magnetic fields.
"If we can generate higher fields," Bang said, "All of the electromagnetic applications are promising."
And pushing to ever higher fields remains Bang’s focus. He’s already setting a goal to top this record.
"There are many, many things left and many details still to understand," he said, "This is just another step. We are still fighting for 50 tesla."
Little Big Coil is a collaborative project primarily supported by the DOE Office of Fusion Energy Sciences Grant DE-SC0022011. The National High Magnetic Field Laboratory is supported by the U.S. National Science Foundation Cooperative Agreement No. DMR-2128556 and the State of Florida. The work is also collaborative with the Groups of Professor Seungyong Hahn at Seoul National University in Korea and Professor So Noguchi at Hokkaido University in Japan.
