複合高温超伝導体の熱的な電流輸送容量劣化の研究 Thermal degradation study of current-carrying capacity of composite high-Tc superconductors
ROMANOVSKII Vladimir，渡辺 和雄，淡路 智，西島 元（東北大）
kwata@imr.tohoku.ac.jp
Abstract: Possible stable finite temperature rise of a superconductor leads to the specific current stability conditions. The formulated criterion indicates that not only negative value of dJc/dT but its temperature variation in the range， which is not close to the critical temperature of a superconductor， has specific influence on the current instability onset. Thereby， the current instability in composite high-Tc superconductors may be absent at relatively high operating temperatures. According to this superconductor｡ﾇs thermal behavior， the thermal degradation mechanism takes place. It depends on the volume fraction coefficient， critical current density of a superconductor at bath temperature， external magnetic field and cross-section of a composite under given cooling conditions. In particular， it is shown that the higher the volume fraction coefficient， the higher difference between the critical current and currents leading to the instability. Therefore， the thermal runaway currents do not increase proportionally to the proportional increase of the volume fraction coefficient.