Research Moves Science Closer to 30 Tesla Superconducting Magnet
February 12, 2007
Contact:
For Magnet Lab: Susan Ray, (850) 644-9651
sray@magnet.fsu.edu
For Northwestern: Megan Fellman, (847) 491-3115
fellman@northwestern.edu
TALLAHASSEE, Fla. — Research conducted at the National High Magnetic Field Laboratory has identified the high-temperature superconductor bismuth-2212 as a material suitable for the new wires needed to build one of the scientific community's holy grails: A 30-tesla superconducting magnet.
Led by Northwestern University physicist William P. Halperin, a team of researchers found that Bi-2212 could be operated at the same temperature as magnets made with niobium – 4 Kelvin – and also achieve the stable state necessary for a 30-tesla magnet.
The findings were published online Feb. 11 by the journal Nature Physics.
"We are exploring nature's limitations, and our discovery has basic implications for the study of superconductors and for applications to magnetic resonance imaging," said Halperin. "The dream would be to have powerful magnets that don't require helium for cooling. Some day new materials might be discovered where this restriction is lifted, but it isn't possible at the present time."
Niobium, the low-temperature material currently used in high field magnets and in magnetic resonance imaging machines, has been pushed almost as far as it can go, to around 21 tesla. (Tesla is used to define the intensity of the magnetic field.) There are no superconducting magnet wires currently available that can generate 30 tesla.
A superconductor, when cooled to its appropriate temperature, conducts electricity without any resistance. Superconductivity first appears in Bi-2212 at a high temperature of 90 Kelvin, but Halperin and his colleagues found that the stable state required in high-magnetic fields can be established only when the temperature falls below 12 Kelvin. The team is the first to establish this limit for Bi-2212.
The experiments were conducted at the National Science Foundation-supported Magnet Lab in a magnet that is particularly suited to condensed matter nuclear magnetic resonance (NMR), Halperin's area of expertise. The magnet was recently refurbished with a new set of coils that allow it to reach higher and more stable fields.
"For us to do our work we need the infrastructure and high level of technical expertise available to the users of the Laboratory," said Halperin, who also is chair of the Magnet Lab's external advisory committee. "The environment there for magnetic field science is the very best in the world."
Scientists at universities, national laboratories and pharmaceutical companies use magnetic resonance technology to study DNA, proteins and other complex molecules. The quest for higher field superconducting magnets is led by the Magnet Lab, which is home to the highest field (21.1 tesla), wide bore (105 mm) magnet in the world. This magnet, the first and only of its kind, was engineered and built at the Magnet Lab. Building a 30 tesla superconducting magnet is a goal set up by the National Research Council, because such a magnet could drive significant advances in chemistry, biology and medicine.
"Now that we have this information about Bi-2212, the next question is, 'Can such a magnet actually be made?'" said Halperin. "I really don't know – it depends on engineering and processing the materials to make them into wires. My fellow scientists and engineers will have to solve the materials problems, and they don't like to accept no as an answer."
In addition to Halperin, the research team includes his graduate student and lead author, Bo Chen, Vesna F. Mitrovic of Brown University, and Arneil P. Reyes and Philip L. Kuhns, of the Mag Lab, as well as crystal growers Prasenjit Guptasarma of the University of Wisconsin-Milwaukee, and David G. Hinks of Argonne National Laboratory.
The work was supported by the Department of Energy and was performed in the department of physics at Northwestern University and at the Magnet Lab's DC Field Facility in Tallahassee.
This release was adapted and reprinted with permission of Megan Fellman and Northwestern University. William Halperin can be reached at 847-491-3686 or w-halperin@northwestern.edu.
