凝聚态物理
晶界
超导电性
磁通钉扎
磁场
电流密度
材料科学
钉扎力
临界电流
粒度
齐纳钉扎
磁铁
铌
涡流
物理
热力学
冶金
量子力学
微观结构
标识
DOI:10.1088/1361-6668/ac6b5f
摘要
Abstract Nb 3 Sn superconductor is of significant interest for applications in constructing high-field magnets beyond the limit of NbTi. However, its critical current density decreases rapidly at high magnetic fields ( > 12 T) and the state-of-the-art level of Nb 3 Sn superconductors still cannot meet the requirements of the planned future accelerator magnets. The primary flux pinning centers for Nb 3 Sn wire mainly arise from the grain boundaries (GBs). In the present paper, we theoretically investigate, through time-dependent Ginzburg-Landau theory and with graphics-processing unit parallel technique, the vortex pinning and the critical current density in large-scale polycrystalline Nb 3 Sn superconductor by varying the pinning potential of GB and grain size at various magnetic fields. Unlike the conventional dot-like pinning systems, it is found that the critical current is not a monotonous function by suppressing the superconductivity of the GBs. The optimal pinning potential of GB for maximum critical current density strongly depends on magnetic fields. Furthermore, we find that the critical current density can be significantly enhanced by reducing grain size at low magnetic fields, while increase of critical current density cannot always be observed at high magnetic fields. Actually, critical current density even decreases by reducing grain size, which depends on the superconductivity of GBs. The findings in the paper provide theoretical foundations to achieve further improvement of Nb 3 Sn with optimizing the flux pinning.
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