| 摘要 |
<p>A superconductor current lead is constituted by using a thin-wall hollow cylindrical oxide superconductor, which has a current path with a large sectional circumferential length and can be easily formed by compression. A critical current is considered to vary in proportion to the circumferential length in cross section of the current path, and a cylindrical oxide superconductor enables the critical current to increase though its sectional area other than the hollow portion is small. There is hence obtained a current lead that features a high critical current density. The cylindrical superconductor current lead has varying wall thickness to increase its mechanical strength. The wall thickness of the superconductor cylinder is greater on the low-temperature side where there is a margin in the current-carrying capacity. Further, the superconductor has a C-shape in cross section in order to decrease the shielding current that flows when the current is supplied in an AC magnetic field, to suppress the trapping of magnetic field and to eliminate the AC loss. The superconductor current lead is magnetically shielded by using an oxide superconductor that has a small heat conductivity to stop external heat effectively. The connection resistance between the external unit and the magnetic shield is set to be greater than the connection resistance between the external unit and the superconductor current lead. Under steady-state condition, the oxide superconductor magnetic shield works as a magnetic shield and when quenching has developed, it biases an ordinary current to protect the current lead.</p> |
