大型超导磁体绝缘系统成型实时及结构健康检测研究

The electrical insulation is one of the most critical components of large scale superconducting magnets which find wide applications in magnetic confinement fusion, high energy accelerator and magnetic resonance imaging. The electrical insulation of large scale superconducting magnets is practically, uniquely carried out through the Vacuum Pressure Impregnation (VPI) approach. Currently, specifications of the VPI for manufacturing of electrical insulation mainly result from the “try-and-error” in numerous institutes. An approach with respect to real-time monitor of the VPI process is practically significant for magnet reliability, maintainability as well as future mass production. However, no effective approach on this topic has been developed so far. This project proposes a real-time monitoring approach for the manufacturing electrical insulation using the VPI process, which is based on measurements of capacitances of conductor (or cable) turn to conductor (or cable) turn, or conductor (or cable) turn to ground. Then, stray capacitance models will be constructed and checked through more experiments, which can be used as a master curve in future serious production. Since the thermal cycle and operation of magnets inevitably lead to ageing and damage accumulation of electrical insulation of large scale superconducting magnets, the project proposes a structure health monitoring approach based on the Fiber Bragg Grating technology. The influence of low temperature, high electrical field and high magnetic field on the measurement of stress/strain field of insulation materials with FBG technology will be investigated.

绝缘系统是磁约束热核聚变、高能加速器以及磁共振成像等大型超导磁体的一个关键部分。针对大型超导磁体绝缘系统制造普遍采用的真空压力浸渍成型，目前主要采用基于“试错法”的固化参数控制法，尚无可靠实时检测方法。项目提出通过研究真空压力浸渍成型过程中导体匝间及导体对地电容实时演变行为并确定合适的电容模型或“通用曲线”以指导大型超导磁体绝缘系统制备。此外，超导磁体降温、升温以及运行都会造成绝缘系统老化和损伤积累，因此开展绝缘材料结构健康检测研究对超导磁体可靠运行具有重要意义。项目拟研究使用光纤光栅FBG的绝缘结构健康检测研究。探索低温、强电场以及强磁场对FBG测量绝缘材料应力应变场的影响行为，为未来大型超导磁体绝缘系统结构健康检测提供参考。

绝缘系统是磁约束热核聚变、高能加速器以及磁共振成像等大型高场超导磁体的一个关键部分。针对大型高场超导磁体用真空压力浸渍成型的纤维增强环氧树脂基复合材料绝缘系统，项目开展了下列相关研究：采用埋入式电阻应变片和FBG法研究了一种双酚F环氧树脂/胺类固化剂（DETDA）和一种基于双酚A环氧树脂的树脂体系（IR-3）成型及温度循环应变响应行为；研究了负热膨胀材料（ZrW2O8）改性环氧树脂和玻纤增强环氧树脂成型及室温-低温应变响应行为；采用表面粘贴应变片和FBG研究了碳纤增强环氧树脂基复合材料气瓶温度循环过程应变响应行为；采用FBG研究了9T NbTi超导磁体线圈成型及温度循环过程应变响应行为。项目研究成果为下一代聚变高场超导磁体绝缘系统结构健康监测设计提供了参考。