外磁场下屏蔽装置的磁平衡机理与方法研究

As the detection of biomagnetic signals, the development and the calibration of ultra-sensitive magnetometers and other researches develop, the demands for the nearly zero magnetic field environment are increased too. The key technology to realize the nearly zero magnetic field environment in the earth magnetic field and different kinds of magnetic disturbances is to reduce the magnetic field inside the magnetic shielding device, which means that shielding materials need to be demagnetized. The magnetic equilibration is a new concept of the demagnetization process, which means that the shields in external fields after demagnetization are in equilibrium. The magnetic equilibration is still in lack of the mechanism study and calculation analysis now. To solve the problem, this project proposes a quantitative calculation method of the magnetic equilibration process in 3d shielding device. The project also explores the mechanism that how the magnetic equilibration process determines the residual static field inside shields. The lowest limitation of the magnetic field which can be achieved in shields with the perfect equilibrium state is predicted. The engineering control parameters of the actual magnetic equilibration process are optimally designed. The gradient, stability and noise of the field inside shields are analyzed too. The research results can directly support the construction of high-level magnetic shielding devices, and upgrade the existing conventional magnetic shielding devices, thus promote researches in the measurement of weak magnetic signals.

随着生物弱磁信号检测、高灵敏度磁传感器研发标定等研究的发展，近零磁场环境的需求日益增加。在地磁场和各类干扰磁场下，实现近零磁场环境的关键在于降低屏蔽装置内部磁场，即屏蔽材料退磁技术。磁平衡是退磁的新概念，是指在外磁场下通过退磁技术使得屏蔽装置达到磁平衡状态的过程，但目前还缺乏机理研究和计算分析。针对这一问题，本项目提出可以适用于三维屏蔽体的磁平衡动态过程定量计算方法；研究磁平衡过程决定屏蔽内部剩余静态磁场的机理；预测屏蔽达到理想磁平衡状态时的内部磁场最低极限值；对实际磁平衡过程的工控参数进行最优化设计；并分析屏蔽内部磁场的梯度、稳定性、噪声等参数指标。研究成果可直接支撑高水平磁屏蔽装置的建设、提高常规磁屏蔽装置的现有指标，进而促进弱磁测量领域的技术进步。

屏蔽材料在屏蔽外界磁场的同时，自身也被磁化，材料自身磁场成为高端屏蔽装置内部磁场的主要限制因素。退磁技术可以消除材料磁化强度的影响，其技术进步主要依赖于著名零磁装置的实践经验，缺乏机理分析和理论研究。针对这一问题，本项目：提出外磁场下屏蔽装置的磁平衡概念，通过促使外磁场下材料内部磁场达到最小能量的磁平衡状态，降低装置内部剩余静态磁场10倍以上。提出外磁场下磁平衡过程的定量计算方法，阐述磁平衡过程决定剩余静态磁场的机理，预测磁屏蔽装置的所能实现的近零磁场极限值。提出新型分布式退磁线圈，已经于2019年应用于德国联邦物理技术研究院柏林零磁室的升级和瑞士保罗谢勒研究所（PSI）的新建零磁装置，并应用于我国空间环境地面模拟装置大科学工程。基于上述突破性技术，实现了在0.5m×0.5m×0.5m空间内的绝对磁场三方向分量均小于0.1nT，该指标已经达到世界第一。国际EDM联合会主席chupp教授在现代物理评论（Reviews of Modern Physics，影响因子36.917）发表文章，评价申请人论文体现了磁屏蔽技术的最新水平。基于最新水平的零磁环境，将促使大量科学研究开展新一代研究实验，例如测量基本粒子磁场并推进EDM测量极限、测量神经电流磁场形成新一代脑磁图研究成果等等。