A 700-mm bore superconducting magnet was built and operated in our laboratory to demonstrate the feasibility of newly developed MgB2 superconductor wire for fabricating MRI magnets. The magnet, an assembly of 10 coils each wound with a reacted and s-glass insulated wire ∼1-km long, was immersed in solid nitrogen rather than in a bath of liquid cryogen. This MgB2 magnet was designed to operate in the temperature range 10-15 K, maintained by a cryocooler. A combination of this "wide" temperature range and immersion of the winding in solid nitrogen enables this magnet to operate under conditions not possible with a low temperature superconductor (LTS) counterpart. Tested individually at 13 K, each coil could carry current up to 100 A. When assembled into the magnet, some coils, however, became resistive, causing the magnet to prematurely quench at currents ranging from 79 A to 88 A, at which point the magnet generated a center field of 0.54 T. Despite the presence of a large volume (50 liters) of solid nitrogen in the cold body, cooldown from 77 K to 10 K went smoothly.
Bibliographical noteFunding Information:
Manuscript received August 29, 2007. This work was supported by the National Institute of Health. W. Yao, J. Bascuñán, W.-S. Kim, S. Hahn, and Y. Iwasa are with Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 USA (e-mail: firstname.lastname@example.org). H. Lee was with the Francis Bitter Magnet Laboratory at Massachusetts Institute of Technology, Cambridge, MA 02139, USA. He is now with the Department of Materials Science & Engineering, College of Engineering, Korea University, Seoul 136-701, Korea (e-mail: email@example.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASC.2008.920836 Fig. 1. Photograph of the cross section of 0.84-mm diameter 18+1 multifilament MgB wire, with key components identified .
- High-temperature superconductors
- Magnetic resonance imaging (MRI)
- Solid cryogen
- Superconducting magnets
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering