Bi-2223 Innermost Coil for 1.03 GHz NMR Magnet

Because of their high critical fields, high-T_c superconductors (HTS) are considered to be the only solution to dramatically increase the highest fields of NMR magnets. We have successfully demonstrated that a 500 MHz HTS/LTS NMR system with a Bi-2223 innermost coil could be used for solution NMR in a driven-mode operation. As the next step, the upgrade of the 920 MHz NMR system installed at the Tsukuba Magnet Laboratory is underway. The innermost Nb₃Sn coil has been replaced by a Bi-2223 coil. The coil was fabricated as a layer-wound coil using five Bi-2223 conductors reinforced with bronze tapes. It was connected in series with the outer Nb₃Sn and NbTi coils. The magnet is expected to generate a field of 24.2 T (1.03 GHz of ¹H resonance frequency) at an operating current of 244.4 A. The test using the Bi-2223 coil and the outer Nb₃Sn coils in combination was successfully carried out. The coil has been installed in the 1.03 GHz NMR magnet. Its cooling and operation are scheduled to take place within Fiscal Year 2010.