超导离子源铌三锡六极线圈镜像磁场约束结构的优化设计

中国科学院近代物理研究所正在进行国际首台45 GHz全铌三锡超导离子源FECR(Fourth Electron Cyclotron Resonance)磁体的研制，该离子源磁体线圈由六个铌三锡超导六极线圈和四个铌三锡超导螺线管线圈组成。由于单根超导线绕制异形六极线圈(非标准鞍型)技术难度大，且铌三锡超导性能对应力敏感，为了测试单个铌三锡六极线圈性能能否达到设计指标，基于铝合金壳层结构和Bladder-Key精确预紧技术，设计了镜像磁场约束结构。本工作主要阐述了运用ANSYS参数化设计编程对镜像磁场结构进行优化设计的过程和优化后的镜像磁场结构，确定了室温预应力大小，并给出了线圈经过室温预紧、冷却降温和加电励磁后的最大等效应力。进一步结合实际六极线圈制作公差(±0.1 mm)，分析和评估了公差对镜像磁场结构中六极线圈预应力施加的影响。

Optimum Design of the Magnetic Mirror Structure for Testing Nb3Sn Sextupole Coil

The Institute of Modern Physics, Chinese Academy of Sciences is developing the new Nb₃Sn superconducting magnet system for the fourth-generation 45 GHz ECR source(FECR). The FECR magnet coils includes six Nb₃Sn superconducting sextuple coils and four Nb₃Sn solenoid coils. Because of the technical difficulty of winding shaped sextupole coils (non-standard saddle type) from a single superconducting wire and the stress sensitivity of Nb₃Sn superconductivity, a magnetic mirror structure based on an aluminum shell-based structure and Bladder & Key technology was devised to test whether the performance of a single Nb₃Sn sextupole coil can meet the design specifications. This paper describes the detailed optimum design process of the magnetic mirror structure using the ANSYS Parameter Design language (APDL), presents the optimized mirror structure, the determination of the room-temperature prestress and gives the maximum equivalent stress during room temperature assembly, cool-down, and magnet excitation. Furthermore, the effects of the pre-stress applied to the sextupole coil in the mirror structure was also analyzed and assessed in the context of the sextupole coil fabrication tolerance (±0.1 mm).