高场中应变下基于稳定性和AC损耗特性的铌三锡CICC导体优化设计模型研究

In response to the impact of magnet fields about 12 Tesla caused by high-current fast excitation, the Nb3Sn Conductor of the partial coils in the devices of ITER (International Thermal-nuclear Experimental Reactor) and HMF (High Magnetic Field) has been introduced. However, the strain from Lorentz Forces and thermal disturbance brings about a deterioration of the stability and AC loss associated with the conductor structure. For the problem of performance degradation from conductor design under strain, an optimization design method of CICC (Cable-in-Conduit Conductor) is presented based on the stability and the AC loss. So, the aim of this project is to study the strain scale law and critical performance degeneration of superconducting wire, and the parameters model of analysis and calculation was established to characterize stability of conductor. The mapping relationship between strain and pinning force in wide strain range and high transient electromagnetic field is found with many parameters such as superconducting filaments and Cu-to-non-Cu ratio. Furthermore, in the complex change magnet field, the space distribution of strain, which caused from electromagnetic force and thermal load, is well analyzed. The matrix analysis model of contact resistance for strands and sub-cable is established. The elastic-plastic deformation is simplified to spring damping model, and the relationship between subcalbe void fraction and the complex strain is obtained. Then, the new mechanism of AC loss for Nb3Sn-based conductor from strain effect is built. The Research on extremum calculation method of energy margin and the AC loss was carried out, and nonlinear mathematical programming method with multivariable restriction such as Cu-to-non-Cu ratio, the number of sub-cable, void fraction and twist pitch is designed. In the end, the optimization design theory of conductor structure is constructed. The study on the project will strengthen realization for stability analysis and AC loss mechanism of Nb3Sn-based CICC with strain, and provide a theory basis for reasonable design of CICC in engineering.

为应对大电流快速励磁时12T高场冲击，聚变和强磁场等装置上的部分线圈已采用铌三锡导体，但电磁和热载荷的应变导致与导体结构有关的稳定性和AC损耗恶化。针对应变下导体设计带来的性能退化问题，提出基于稳定性和AC损耗特性的CICC导体优化设计方法。研究高场中铌三锡超导线应变标定律和临界特性退变机制，构造表征导体稳定性的参数分析模型。探索宽应变区间内超导芯丝和铜超比等表达的应变与钉扎力映射关系，以及高场中大电流励磁时电磁力和热载荷的应变空间分布，建立应变下子缆间接触电阻的矩阵计算方法，把弹塑性变形简化为弹性阻尼模型，获得应变与子缆空隙率间函数，揭示高场应变下导体AC损耗产生机理。研究能量裕度与AC损耗极值化计算模型，设计铜超比及子缆根数、空隙率和扭距等多变量制约的非线性数学规划方法，构建CICC导体优化设计理论。以此加强对应变下铌三锡导体稳定性和AC损耗机理认识，为工程上合理设计导体提供理论思路。

为应对大电流快速励磁时12T高场冲击，聚变和强磁场等装置上的部分线圈已采用铌三锡导体，但电磁和热载荷的应变导致与导体结构有关的稳定性和AC损耗恶化。针对应变下导体设计中性能退化问题，提出基于稳定性和AC损耗特性的CICC导体优化设计方法。研究了高场中铌三锡超导线应变下临界温度退变计算模型，构造了表征导体稳定性的参数分析模型。探索了高场中大电流励磁时电磁力和热载荷的应变分布，建立了应变下子缆间接触电阻的计算方法，获得了应变与子缆空隙率间函数，揭示了高场应变下导体耦合损耗产生机理。形成温度裕度与AC损耗计算模型，设计了铜超比及子缆根数、空隙率和扭距等多变量制约的非线性数学规划方法，构建了CICC导体优化设计理论。以此加强对应变下铌三锡导体稳定性和AC损耗机理认识，为工程上合理设计导体提供理论思路。