In-Field Evaluation of REBCO Superconducting Joint

Joint resistance and current-carrying capacity of the intermediate grown superconducting (iGS) joint were evaluated at temperatures at 4.2 K and 77 K in magnetic fields up to 3 T. The evaluations were done using the joint resistance evaluation system that we have developed. This system utilizes a current decay method. We have improved sensitivity and quantitativeness of the current measurement using a split-core current transformer with a Hall sensor. The joint resistance (R-j) was evaluated to be 9.6 x 10(-15) omega and 2.3 x 10(-14) omega at 4.2 K in self-field and in 3 T, respectively. The residual currents were 306 A in self-field and 296 A in 3 T. This indicates that the iGS joint has sufficiently high current-carrying capacity at 4.2 K in 3 T. In addition, R-j of the iGS joint does not show magnetic field dependence up to 3 T at 4.2 K. At 77 K, the injected currents rapidly decreased and evaluated in-field R-j was order of 10(-11) omega. This relatively higher R-j is considered to be due to a high load factor of similar to 100% at the joint. However, the residual current was observed even in 3 T, which indicates that the iGS joint can be used above 4.2 K in magnetic fields.

Automated summary

We evaluated the joint resistance and current-carrying capacity of the intermediate grown superconducting (iGS) joint at low temperatures and high magnetic fields using a specially developed evaluation system. The results showed that the iGS joint has a sufficiently high current-carrying capacity at 4.2K in a 3T magnetic field and does not exhibit magnetic field dependence. However, at 77K, the joint resistance was relatively high due to a high load factor.