Evaluation for characteristics of Bi-system high temperature superconducting wires under large electro-magnetic stress

大电磁应力下双系高温超导线材特性评估

基本信息

批准号：
11650672
负责人：
WATANABE Kazuo
金额：
$ 2.18万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Superconducting properties under the large electro-magnetic stress state of Hoop or compressive stress were examined for a Ag-sheathed Bi2212 tape coil cowound with reinforcing tape. Further, the thermal stability characteristics for the test coil were also studied, aming to an application for a cryocooled superconducting magnet. Especially, we focused on the flux flow state of high temperature superconductors, and investigated the possibility whether such a stable flux flow resistivity without quenching could be applied as a new magnet technology or not.As a new attempt to overcome the large Hoop stress, the residual compressive strain for Bi2212 tape was added by tension-winding of Hastelloy alloy tape. This results in standing with the large stress of 270 MPa for Ag-sheathed Bi 2212 tape reinforeced with Hastelloy alloy tape. Moreover, the critical current characteristics in a transverse compressive strain state were measured for the Ag-sheathed Bi2212 test coil with Hastelloy reinforcing tape. An apparatus for measuring the transverse compressive strain effect in the critical current was installed into a cryogenfree superconducting magnet at the High Field Laboratory for Superconducting Materials. The transport current properties depending upon the reinforcement method were compared with each other, varing the applied magnetic fields up to 10 T.It was found that the Ic degradation of 40 % was occurred at the transverse compressive stress of 10 MPa for the Ag-sheathed Bi2212 tape coil without reinforcement, and that the same degradation corresponded to the reinforcing Bi2212 tape coil at 40 MPa. From the experimental results on the thermal stability for the Ag-sheathed Bi2212 tape, we can understand that the thermal stability in the cryocooling condition is closely related with the cryocooling power, and that the heating state above Ic is stabilized enough by keeping the cooling balance.

研究了带有加强带的Ag护套Bi2212带状线圈在环向大电磁应力或压应力状态下的超导性能。此外，针对低温冷却超导磁体的应用，还研究了测试线圈的热稳定性特性。特别是，我们重点研究了高温超导体的磁通流状态，并研究了这种无需淬火的稳定磁通流电阻率是否可以作为一种新的磁体技术应用的可能性。作为克服大环向应力的新尝试， Bi2212带材的残余压缩应变是通过哈氏合金带材的张力缠绕来增加的。这导致哈氏合金带增强的Ag护套Bi 2212带能够承受270 MPa的大应力。此外，还测量了带有哈氏合金增强带的Ag护套Bi2212测试线圈在横向压缩应变状态下的临界电流特性。在超导材料高场实验室的无制冷剂超导磁体中安装了用于测量临界电流中横向压缩应变效应的装置。将所施加的磁场变化至 10 T 时，对不同加固方法的输运电流特性进行了比较。结果发现，Ag 护套的横向压应力为 10 MPa 时，Ic 下降了 40%。没有增强的 Bi2212 胶带线圈，并且在 40 MPa 下与增强的 Bi2212 胶带线圈对应的相同退化。从Ag护套Bi2212带的热稳定性实验结果可以看出，低温冷却条件下的热稳定性与低温冷却功率密切相关，并且通过保持冷却平衡，Ic以上的加热状态足够稳定。