EFFECTS OF FLUX CREEP ON A SUPERCONDUCTING SOLENOID WITH HIGH-TC OXIDE SUPERCONDUCTORS

The normalized decay rate of a persistent current due to thermally activated flux creep is discussed theoretically for the case of a long superconducting solenoid wound with wires of superconducting tape. It is shown that the normalized decay rate of the transport current in the solenoid for the persistent current mode is smaller than the normalized decay rate for magnetization of the superconducting tape. Furthermore, these values are related by the ratio of the superconducting film thickness in the tape to the bore radius of the solenoid, as far as the initial creep process is concerned. The duration of the initial creep process, during which the total flux inside the solenoid is conserved, depends exponentially on the effective pinning potential, Uc. Even at 77 K, therefore, the period can be increased to several years or more by a slight increase in the value of Uc in high Tc superconducting wires. © 1990.