GENERATION OF MAGNETIC-FIELDS OVER 21T IN A 61MM CLEAR BORE USING LOWCOPPER RATIO (NB,TI)(3)SN CONDUCTORS

A 21 T superconducting magnet system has been developed and improved a t the National Research Institute for Metals in Japan, qs the steady p rogress of high-Tc superconducting coils required a larger bore for te sting their performance, a new innermost coil has been det eloped. We increased the available bore from 50 mm to 61 mm. The new coil employe d three kinds of rectangular (Nb,Ti)(3)Su conductors. External copper stabilized these conductors, with a Cu:SC ratio df only 0.25. The new coil operated in a 160 mm diameter dear bore with a background field o f 18 T in saturated superfluid helium, generating a central field of 2 1.5 T without any training behavior. A double walled dewar, the outer diameter of which was 60 mm, was also developed. With this dewar, the nem system provides a temperature-variable bore of 50 mm.