性能退化是Nb3Sn导体广泛应用于高场磁体系统的弱点，退扭作为引起导体性能退化的新现象，正作为一个新的研究热点引起越来越多的关注。多重介质、多芯多层级不规则绞缆形成的螺旋结构增强了CICC导体的结构复杂性，数值方法难以准确地进行模拟。本项目旨在通过理论模型和实验相结合的方法，探究导体结构设计、电缆绞制、导体制造及低温运行对退扭的影响。通过对不同材料进行力学性能分析，结合不同的导体结构设计，以导体几何空间结构模型为基础，推导导体扭转模型和差分方程。利用无损检测方法，建立力学实验平台，实现退扭在线检测，并与数值模拟结果进行比对，优化理论模型。本项目的研究结果，能够揭示Nb3Sn导体的退扭机理，提出高场下低扭转率的导体结构设计、制造技术及低温运行分析方法，为高场Nb3Sn导体的设计、制造及应用提供理论与实验依据，并为其它导体的制造提供参考。

Degradation is the main defect to be used in the high magnetic field system.The new spot of reserch on degradation caused by rotation gets more attention widely. The spiral structure caused by irregular cabling with multiple materials, cores, and layers strengthen the complexity of CICC, which is difficult to be simulated by numerical modeling. This program aims to get the mechanism of rotation from theorical model using numerical method and experiment, including conductor design, cabling, conductor manufacture, and conductor operation. Firstly, the mechanical properties of different materilas and conductor design were investigated. The rotation model was developed based on spitial structure model, and the difference equations were investigated. The new experimental method is also investigated. The NDE (Non-Destructive Examination) method is mainly considered. In the process, the theory and experiment device of rotatioin are setup, which could investigate the cause of rotation, and provide valid method to reduce rotation. The results will provide valuable basis for both design and manufacturing of high field Nb3Sn CICC. It can also be used as a reference for other HTS conductor fabrication.