基于行波磁场的无接触式充磁技术中宏观磁通量子耦合效应的机理研究

High temperature superconducting magnets often operate in the persistent current mode, however, the current in the closed superconducting loop decays due to the magnetic flux creep effect and the presence of the joint resistance. Using conventional external power source to magnetize a superconducting magnet requires the use of a large current power supply device and leads to a huge associated heat losses. This research focus on the study of a novel contactless magnetization technology——a high temperature superconducting flux pumping technology based on traveling magnetic waves, which can inject DC current into the closed HTS system to compensate for the current decay without any electrical contact, and heat losses caused by traditional external power supply current leads can be avoided. Finally，with this technology, we can make superconducting power devices with high-stability magnetic fields , which will make a big contribution to the technical innovation of a variety of engineering applications, ranging from public transportation, through medical equipment, to high energy physics. Based on the second-generation high temperature superconducting Coated Conductor(CC) coils，this research utilize traveling magnetic fields generated by DC drive source to magnetize the superconducting coil. The relationship between the magnetizing efficiency and the frequency, wavelength, amplitude and direction of traveling magnetic field are investigated by systematically measuring and analyzing of the electromagnetic characteristics of the HTS CC coils. The finite element method(FEM) is used to numerically study the magnetization and AC loss of high temperature superconducting tape. The vortex dynamics method is also introduced into the modeling of vortex cluster motion. Upon comprehensively studying the experimental data and numerical simulations, this research also explores the physical mechanism of HTS flux pumping effect and the microscopic mechanism of macroscopic magnetic coupling phenomenon, revealing the physics underlying the flux pumping effect based on the traveling magnetic waves, finally providing the theoretical support and technical assurance to realize the steady-state strong magnetic fields for high temperature superconductors.

高温超导磁体在持续电流模式下工作时，由于磁通蠕动效应和接头电阻的存在，使得闭合超导回路中的电流产生衰减。应用传统外部电源为超导磁体充磁需要采用大电流供电设备，能量损耗大。本项目致力于研究一种新型无接触式充磁技术——基于行波磁场的高温超导磁通泵，它可以在没有电接触的情况下将直流电流注入超导闭环系统，以补偿电流衰减，避免传统电源电流引线造成的热损耗。利用这种技术可以制造具有高稳定性磁场的超导新能源器件，这将对公共交通、医疗设备及高能物理等工程应用领域的技术革新做出贡献。本项目基于第二代高温超导涂层导体线圈，利用直流驱动源产生行波磁场对超导线圈进行充磁，定量研究行波磁场特征参数与超导材料特征物理量之间的关系，利用有限元法对高温超导带材的磁化及交流损耗进行数值分析，并将磁通动力学方法引入涡旋簇运动的建模中，探索高温超导磁通泵效应与宏观磁通量子耦合效应的微观机制，从而为实现稳态强磁场提供理论支持。

高温超导磁体在持续电流模式下工作时，由于存在接头电阻、磁通蠕动及交流损耗效应，将导致闭合超导回路中电流衰减。应用传统外部电源为超导磁体充磁需要采用大电流供电设备，能量损耗大，容易导致磁体失超。经过3年艰苦攻关，我们攻克了传统电流引线漏热问题，实现了大电感高温超导磁体闭环运行，利用这种技术可以制造具有高稳定性磁场的超导新能源器件。这将对国防军事、公共交通、医疗设备及高能物理等工程应用领域的技术革新做出贡献。项目利用COMSOL有限元仿真软件搭建高温超导线性磁通泵三维模型，得出结论：i=1A，f=10Hz，gap=1mm，Ф=120°时，气隙中磁感应强度最优。此外，基于第二代高温超导涂层导体线圈，利用有限元法对高温超导负载双饼线圈的磁化及交流损耗进行数值分析。随着传输电流幅值的增大，YBCO线圈的磁场在不断增强，这就会导致整体的交流损耗增大。交流损耗与频率无关。在传输电流较小时，外加磁场对线圈交流损耗的影响较大，传输电流较大时(传输电流与临界电流比值大于0.5)，外加磁场对线圈交流损耗的影响较小。随着传输电流幅值的增加，交流损耗随相位差的变化幅度更大，而传输电流小于20A时，相位差的影响可以忽略不计。本研究探索高温超导磁通泵效应与宏观磁通量子耦合效应的微观机制，通过对磁通泵励磁过程的仿真分析与试验研究，课题组发现磁通量子耦合效应可应用于描述超导材料中磁通量子宏观分布情况，而无法准确解释磁通泵现象的微观物理机理。鉴于此，湖南大学超导与新能源中心创新性地提出宏观磁通量子扩散-整流机制，以解释不能用经典电磁感应理论描述的超导带上交变磁场感生直流电压的物理起源，从而为磁通泵技术的进一步应用提供理论基础与技术支撑。