Development and characteristics of persistent mode in HTS magnet

We fabricated a high-temperature superconducting (HTS) magnet with a persistent current switch (PCS) and evaluated the decay characteristics of persistent mode and joint resistance at 77 K. To make the HTS magnet, BSCCO(2223) tapes were wound into a double-pancake coil and connected to the PCS by soldering. Field decay behavior was remarkably dependent on operating current. At an operating current of 50% of the critical current (I_c), decay behavior showed two distinct regimes: initial fast decay and subsequent linear decay. By contrast, there was a linear decay regime of only 13% of I _c. Total circuit resistance was approximately 2.0×10 ^-8 Ω at an operating current of 6 A. Measured decay behavior was closely consistent with the calculated decay behavior obtained from both the index resistance and joint resistance components.