MIT team finds that the ratio of component atoms is vital to performance.
The newest hybrid magnet at the Massachusetts Institute of Technology's Francis Bitter National Magnet Laboratory has broken its own world record, achieving a sustained magnetic field of 37.2 tesla, about 700,000 times greater than the Earth's magnetic field.
John Williams, head of the laboratory's magnet technology division, describes the hybrid magnet as a combination of a newly designed, high-power, water-cooled magnet, capable of producing 21.5 tesla, which is placed inside the room-temperature bore of a superconducting magnet, capable of producing 12.7 tesla.
The record of 34.2 tesla set on Dec. 10, 1992, by the MIT laboratory using the new hybrid magnet was extended on Dec. 17 to 37.2 tesla using ferromagnetic pole pieces as concentrators. The pole pieces are made of holmium, a metallic element that provides higher fields than iron at low temperatures.
Breaking the world record required 10 million watts of power delivered to the water-cooled magnet while maintaining the superconducting magnet surrounding the water-cooled magnet in a bath of liquid helium of at a temperature of 1.7 kelvin (-456 degrees Fahrenheit).
The previous world record for a sustained high magnetic field was 35.3 tesla and was set by the MIT laboratory in 1988. At that time the record 31.8-tesla hybrid magnet was enhanced by the similar ferromagnetic pole pieces to produce 35.3 tesla in the 2 millimeter gap between the pole pieces.
The $6.3 million project was begun in 1986. The new hybrid is the fourth in a line of magnets developed over a 16-year period by MIT engineers with National Science Foundation support.
The Francis Bitter National Magnet Laboratory is funded by the NSF and operated by MIT as a facility for more than 300 scientists and engineers in the United States and abroad whose experiments and theoretical studies make use of high magnetic-field technology. Superconductivity, materials science, medicine, biology, chemistry, physics and engineering are among such fields. Research in these areas could have a major impact on the development of materials for the computer, electronics, communications, magnetics, transportation and electrical utility industries in the United States, said Professor Robert G. Griffin, director of the Magnet Laboratory.
Construction of the record-setting magnet involved the support of several Massachusetts high-technology firms, including Janis Research of Wilmington, Koch Process Systems International of Westborough and Supercon of Shrewsbury.
A version of this article appeared in the January 6, 1993 issue of MIT Tech Talk (Volume 37, Number 17).