First some background
Nuclear magnetic resonance (NMR) is an important technique for probing and characterizing the structure of proteins and other complex materials. The higher the magnetic field, the more detail scientists can see.
The strongest NMR magnets available today max out at about 24 teslas due to limitations of the materials they are made of, the low-temperature superconductors niobium-tin (Nb3Sn) and niobium-titanium (NbTi). To get to higher fields for NMR magnets, magnet engineers would need to use high-temperature superconductors (HTS), which don’t suffer from the same constraints as Nb3Sn and NbTi.
To meet the demands of scientists for stronger NMR magnets, the National MagLab has been investigating three promising HTS materials to use in magnet coils: REBCO (rare-earth barium copper oxide), bismuth-2212 and bismuth-2223.
What did scientists discover?
MagLab scientists have successfully tested a new variant of Bi-2223 supplied by Sumitomo Electric. Wound with 240 meters of tape, the coil was tested in liquid helium at 4.2 K with a background field of 14 teslas. The coil generated an additional 5.5 teslas for a total magnetic field of 19.5 teslas.
The material operated successfully at a strain (0.8%) and current density (243 amps per square millimeter) consistent with conceptual designs of a hypothetical 30-tesla all-superconducting NMR magnet.
Based on those test results, MagLab engineers have developed a conceptual design using a combination of low-temperature superconductors and Bi-2223 coils that should achieve 30.5 teslas in a 1.3 GHz NMR system. More test coils are being built to develop this project.
Why is this important?
To get to higher fields for NMR research, high-temperature superconductors, cooled to 4.2K, are required.
Who did the research?
W.S. Marshall, M.D. Bird, D.C. Larbalestier, D.M. McRae, P.D. Noyes, A.J. Voran, R.P. Walsh, E. Arroyo
Why did this research need the MagLab?
The MagLab has the personnel, equipment and organizational knowledge required to successfully build layer-wound superconducting coils operating in such extreme conditions. Many of the coil technologies used were adapted from previous work on the MagLab's 900MHz NMR/MRI magnet and 32T all-superconducting magnet.
Details for scientists
- View or download the expert-level Science Highlight, Bi-2223 High-Temperature Superconducting Test Coils for NMR Magnets
- Read the full-length publication, Bi-2223 Test Coils for High-Resolution NMR Magnets, in IEEE Trans Appl Supercond
This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490); W.W Brey, U.P. Trociewitz (NIH R21GM111302)
For more information, contact Mark Bird.