A cryogen-free superconducting magnet with 95 cm warm bore for whole body MRI

A 0.5 T, 95 cm warm bore, cryogen-free superconducting magnet for whole body MRI has been developed and tested. By using Nb3Sn tape superconductor, this magnet is designed to meet the same performance requirement as existing helium cooled MRI magnets. Persistent operation with drift rate less than 0.1 ppm/hour and a stable 5.6 ppm field homogeneity in a 30 cm/spl times/40 cm cylindrical volume was achieved in October 1992. The magnet is cooled and maintained at the temperature of about 10 K by a Gifford McMahon (G-M) cryocooler. High quality images were produced by using this magnet with the 0.5 T GE SIGNA magnetic resonance imaging system.