Development and operation of superconducting NMR magnet beyond 900 MHz

As a milestone in the 1-GHz NMR magnet project being carried out at the Tsu kuba Magnet Laboratory, a 900-MHz class NMR magnet was successfully manufac tured and operated in December 1999. The developed magnet is made of 15%Sn- bronze-processed (Nb, Ti)(3)Sn, Ta-reinforced (Nb,Ti)(3)Sn, and NbTi conduc tors, The room temperature bore of tile cryostat is 54 mm in diameter. AII the coils are cooled with pressurized superfluid helium, The magnet generat ed a field of 21.20 T in a driven mode and then operated in a persistent mo de at 21.17 T corresponding to a proton NMR frequency of 902 MHz. The field may be raised to the range of 21.6 T (920MHz) in the near future.