Properties of a few hundred A class Y-Ba-Cu-O bulk current leads usable in magnetic fields

In order to investigate the properties of high-temperature Y-Ba-Cu-O bulk current leads usable in magnetic fields, a prototype having a 250 A current capacity at 77.3 K and 0.5 T has been fabricated using melt-processed bulk superconductors, QMG. The critical current was larger than 800 A at an applied field of 0 T and larger than 500 A at 0.5 T. When a current of 250 A was continuously applied for 10 min at 0.5 T, no change was observed in the voltage between the current lead ends. When the current lead was exposed to a repetition of thermal cycles between the liquid nitrogen temperature and room temperature, the transport properties did not change in the experimental range. The amount of heat leak through the current lead can be estimated to be about 0.095 W when the high-end temperature is 77.3 K and the low-end temperature is 4.2 K. (C) 2002 Elsevier Science B.V. All rights reserved.