Persistent current HTS magnet cooled by cryocooler (4) - persistent current switch characteristics

We developed a persistent current high temperature superconducting (HTS) magnet for Maglev train. The HTS magnet mainly consists of an HTS coil, a persistent current switch (PCS), a GM type two-stage pulse tube cryocooler. A PCS is one of the most important components to maintain persistent current operation. A YBCO thin film was adopted for a PCS conductor because it has a high resistivity over a critical temperature and a high critical current density at lower temperatures. Persistent current mode operation tests were successfully carried out with the PCS. The current decay rate at the rated current operation of 532 A was 0.44%/day which was investigated by measuring the magnetic field at the center of the coil.