应用于铯喷泉钟的磁屏蔽系统的设计

Design of Magnetic Shield for Cesium Fountain Clock

高质量磁屏蔽系统是铯喷泉钟的重要部件之一。首先给出评定磁屏蔽效果的3个指标，即磁场均匀区长度、磁场均匀区起点位置和磁屏蔽效率。在此基础上，讨论了利用有限元计算3层磁屏蔽系统的层间径向间距、轴向间距、端盖孔套管长度和端盖连接方式对磁屏蔽的影响，给出了相应的优化参数，并对比了按优化参数设计的3层磁屏蔽与原有4层磁屏蔽系统用有限元计算的磁屏蔽效果。有限元计算结果为中国计量科学研究院新铯喷泉钟磁屏蔽系统的技术设计提供了理论指导。

The high quality magnetic shielding system is one of the most important components of cesium fountain clock. Firstly, the three parameters for magnetic shielding performance evaluation were defined, i. e. uniform range, the starting position of uniform range and shielding factor. And then, the results for different configurations of three layer cylindrical magnetic shield sets using finite element calculation are presented. In particular, effects on shielding of radial and axial spacing between shield layers, the length of sleeves weld on the end cap and the connection geometry between end caps and shield cylinders are examined. From the calculation results, the performance of optimal configuration of three layer shield sets is compared with the four layer ones used in NIM5 cesium fountain clock. This is important in design and assemble the magnetic shielding for the next generation cesium fountain clock to improve the accuracy.